We programmed the thermostats and the ERV (energy recovery ventilator) and we discovered something really nice: The air is really really fresh inside the house. It is almost crisp. I think it is a combination of 3 things:
1) The new system is more appropriately sized for our house. Our old system would blow cold air forcefully and then shut off. The new system seems to be more gentle with its temperature adjustments.
2) The new thermostats have a programmable fan. We have it set to run for 10 minutes every hour if there has been no heat or air conditioning in the last hour. That helps keep the air from getting stale.
3) The ERV is set to run 30% of the time (18 minutes of every hour). When it runs, the ERV takes air from the 2nd floor bath rooms and replaces it with fresh air from outside the house, dumping the fresh air back in to the 2nd floor air supply ducts. If the HVAC system is running, that fresh air will ultimately get circulated throughout the whole house.
Thursday, September 2, 2010
Sunday, August 29, 2010
Desuperheater - making hot water
The GSHP desuperheater has a pump that pulls water from the holding tank, heats it put by 5 degrees and then dumps this hotter water back in to the holding tank. It'll keep doing this as long as it has heat to dump and the water from the holding tank is below a set temperature. The desuperheater can be set to heat the water to either 125 degrees or 150 degrees. 150 degrees is obviously way too hot to have coming out of the tap so we cut the temperature down with a mixing valve that adds cold water. The nice thing about the 150 degree water is that it serves as a nice heat energy storage tank. We use less hot water from the 150 degree tank than we would from 125 degree tank. So we can use a smaller holding tank as well. The hotter the input water to the ASHP, the less work it has to do.
The hot output of the holding tank feeds the cold input of my air-source heat pump hot water heater. The hot output of the ASHP goes to the house. We use the mixing valve to make sure the water we put in to the ASHP water heater is not too hot. That's the grey knob in the center of the picture above.
There are two aspects that confuse me about the mixing valve: One is that because the GSHP runs intermittently we won't get a full holding tank of water at 150 degrees. So I cannot easily configure the mixing valve knob setting. The second issue I have is about the mixing valve itself and how it works. I had two mental pictures for how it worked. The simple picture was that the knob sets the ratio of hot and cold water that get dumped to its output. The more complex picture is that the knob sets the ratio and that the valve somehow senses the temperature and actively varies the ratio between the hot and cold inputs to set the output temperature. I think the reality is somewhere in between. I need to call the manufacturer of the mixing valve to learn more.
Basically, I think there is some sort of temperature sensing element in the mixing valve and it attempts to vary the ratios between the hot and cold inputs over a small range. But if the hot water is too cold, it reaches a limit and mixes in more cold water than it should. For example, if we set the mixing valve for 150 degree input water from the holding tank then it'll probably work fine if the holding tank is at 140. However it will also likely mix in too much cold water if the holding tank is only at 100 degrees.
My plumber was very smart in installing a temperature sensor on the connection between the holding tank and the ASHP water heater. I hadn't thought of that. But now I'm watching it to try to figure out if the mixing valve is set properly. Due to heat leakage from the ASHP, sometimes we see the heat convecting out of the cold input and raising the temperature observed by the thermometer.
There are two aspects that confuse me about the mixing valve: One is that because the GSHP runs intermittently we won't get a full holding tank of water at 150 degrees. So I cannot easily configure the mixing valve knob setting. The second issue I have is about the mixing valve itself and how it works. I had two mental pictures for how it worked. The simple picture was that the knob sets the ratio of hot and cold water that get dumped to its output. The more complex picture is that the knob sets the ratio and that the valve somehow senses the temperature and actively varies the ratio between the hot and cold inputs to set the output temperature. I think the reality is somewhere in between. I need to call the manufacturer of the mixing valve to learn more.
Basically, I think there is some sort of temperature sensing element in the mixing valve and it attempts to vary the ratios between the hot and cold inputs over a small range. But if the hot water is too cold, it reaches a limit and mixes in more cold water than it should. For example, if we set the mixing valve for 150 degree input water from the holding tank then it'll probably work fine if the holding tank is at 140. However it will also likely mix in too much cold water if the holding tank is only at 100 degrees.
My plumber was very smart in installing a temperature sensor on the connection between the holding tank and the ASHP water heater. I hadn't thought of that. But now I'm watching it to try to figure out if the mixing valve is set properly. Due to heat leakage from the ASHP, sometimes we see the heat convecting out of the cold input and raising the temperature observed by the thermometer.
All systems go!
Wednesday August 25th we had power-on for the GSHP system in cooling mode. The good news is that it appears to work. They finished the duct work, control and thermostat wiring, setting the condensate pumps and running condensate drains for my water heater and GSHP. We even tried out the desuperheater and it appeared to generate hot water.In the picture on the right, you can see the 5 "wet" connections for the GSHP. The two copper pipes are for the desuperheater -- to heat the hot water in the white holding tank. The white pipe is for the condensation. You can see a small condensation pump tucked in behind the black insulated pipes. The black insulated pipes go to the red-and-white pumping station on the wall. That's the ground loop pump.
Our old heating system had two completely isolated furnaces. With the new system, we are using the one GSHP. Naively, I thought they'd just make a pair of Y's with the ducts. One for the first and second floor supply vents and one for the first and second floor returns. Reality is a lot more complicated. The HVAC installer really had to be creative to get all the ducts connected properly. Like air origami!
For the first cooling data, we observed the water leaving the GHSP at 74 degrees and returning from the loop at 64 degrees. Given that the ground loop is in 50 degree earth, I sort of expected it to come back cooler, but I guess the analogy is that even an ice cube takes time to melt at room temperature. The good news is that it is cooling. Need more data to see how efficient it will be.
Lots of little things to finish up on the project. Patching holes in walls, fixing a few things here and there. We spread 3 yards of loam and planted some grass over the weekend. We were fortunate enough to have 5 days of rain to get it started. We need to get some more loam. We did not realize that we would be without so much topsoil after the trenching!!
--
Correction to previous posts: they used propylene glycol not ethylene glycol in the ground loop to keep it from freezing in winter. I was surprised: Propylene glycol is used in soaps and even dog food. I think the loop holds about 80 gallons of fluid. About 20 gallons of that is propylene glycol.
Saturday, August 21, 2010
ERV - Energy Recovery Ventilator
The ERV is great for tight homes to bring fresh air in, condition it, and remove stale air from inside the house.
For the inside work, the big surprise was the length of ducts that the ERV requires. It requires 4 connections: (1) fresh air in from outside, (2) waste air to outside, (3) waste air from inside, and (4) fresh air to inside. I should have realized that means a lot of duct work.
The fresh air from outside (#1) is warmed or cooled by the waste air extracted from indoors (#3) and then the fresh air is pumped in to the house (#4). The waste air from inside (#3) has heat extracted from it (in winter) or added to it (in summer) and is then exhausted externally (#2). The 2 external connections have to be at least 10 feet apart and the intake has to be far from other exhaust sources. The standard thing is to run the to soffits or ducts on opposite side of the house. My soffits were too small so we went for opposite sides of the house.
For the #1 and #2 vents, we need external connections. To avoid cutting more holes in the house, we used a small portion of my existing gable vents (about a quarter). Given that I have soffit and ridge vents, we didn't think this would impact attic air flow too much. I also plan to get a couple of mushroom vents installed when I get my roof replaced (that's the next big project!)
What about the inside stuff (#3 and #4)?
The original intention of doing the ERV was to fix the problem I had with the bathroom vents. The current shower fans draped in to the soffits. Since air wants to go in the soffits, not out, all the moist air from the bathrooms would stay inside the house and rise up the roof sheathing. A bad situation. So we didn't use the bathroom shower fans. Really annoying.
With the ERV, we are able to take the exhaust vents from the shower fans and use them as a source of internal waste air (#3). We also took one of the two HVAC air supply lines from the master bathroom (which we had shut off for years) and converted that in to a another source of waste air for the ERV. That avoided cutting another vent hole in my bathroom.
All that remained was to dump the fresh air (#4) somewhere inside the house. The original goal was to split that duct from the ERV and dump half in to the upstairs supply system and half in to a vent on the first floor. But the first floor vent didn't work out; The chase that we had planned to use was full of other duct work and didn't have any space left. So instead, we are just putting the fresh air in to the second floor HVAC air supply system. I'm happy to just have the bathroom shower vent issue resolved! No more opening a bathroom window in the winter!
Avoiding low-resistance cycling
Given that the bathrooms have both HVAC supply vents (where the fresh air from the ERV is being pushed in) and also the waste-air intakes for the ERV, there is some danger of having the ERV just cycle the air in the bathrooms as that would be the lowest resistance path. To avoid that possible loop, we run the fresh air in to the 2nd floor supply system far away from the bathrooms. This way it should reach all the rooms on the 2nd floor. I have my friend Peter to thank for thinking of the issue.
For the inside work, the big surprise was the length of ducts that the ERV requires. It requires 4 connections: (1) fresh air in from outside, (2) waste air to outside, (3) waste air from inside, and (4) fresh air to inside. I should have realized that means a lot of duct work.
The fresh air from outside (#1) is warmed or cooled by the waste air extracted from indoors (#3) and then the fresh air is pumped in to the house (#4). The waste air from inside (#3) has heat extracted from it (in winter) or added to it (in summer) and is then exhausted externally (#2). The 2 external connections have to be at least 10 feet apart and the intake has to be far from other exhaust sources. The standard thing is to run the to soffits or ducts on opposite side of the house. My soffits were too small so we went for opposite sides of the house.
For the #1 and #2 vents, we need external connections. To avoid cutting more holes in the house, we used a small portion of my existing gable vents (about a quarter). Given that I have soffit and ridge vents, we didn't think this would impact attic air flow too much. I also plan to get a couple of mushroom vents installed when I get my roof replaced (that's the next big project!)
What about the inside stuff (#3 and #4)?
The original intention of doing the ERV was to fix the problem I had with the bathroom vents. The current shower fans draped in to the soffits. Since air wants to go in the soffits, not out, all the moist air from the bathrooms would stay inside the house and rise up the roof sheathing. A bad situation. So we didn't use the bathroom shower fans. Really annoying.
With the ERV, we are able to take the exhaust vents from the shower fans and use them as a source of internal waste air (#3). We also took one of the two HVAC air supply lines from the master bathroom (which we had shut off for years) and converted that in to a another source of waste air for the ERV. That avoided cutting another vent hole in my bathroom.
All that remained was to dump the fresh air (#4) somewhere inside the house. The original goal was to split that duct from the ERV and dump half in to the upstairs supply system and half in to a vent on the first floor. But the first floor vent didn't work out; The chase that we had planned to use was full of other duct work and didn't have any space left. So instead, we are just putting the fresh air in to the second floor HVAC air supply system. I'm happy to just have the bathroom shower vent issue resolved! No more opening a bathroom window in the winter!
Avoiding low-resistance cycling
Given that the bathrooms have both HVAC supply vents (where the fresh air from the ERV is being pushed in) and also the waste-air intakes for the ERV, there is some danger of having the ERV just cycle the air in the bathrooms as that would be the lowest resistance path. To avoid that possible loop, we run the fresh air in to the 2nd floor supply system far away from the bathrooms. This way it should reach all the rooms on the 2nd floor. I have my friend Peter to thank for thinking of the issue.
No more oil!
I had my last visit hopefully forever from my oil company! Yippie! It was actually an apropos ending to the whole oil experience. I had tried to donate the oil to Joe for Oil (A Massachusetts oil-heat assistance program) but they said they didn't have any mechanism for that. So, for the value of the oil in my tank, my old oil company said they'd remove it. Isn't that a generous gesture from them? 2 guys doing less than 30 minutes of work with a 20-gallon-per minute pump. You do the math. Anyway, they pumped the oil from my two tanks through about 100 ft of hose up in 12 ft in to the top of one of their oil delivery trucks. Well, what happens when you turn off a pump that has hose with 100 ft of oil in front of it in it rising up 12 feet in the air?
Oil is dirty and smelly. While some of the oil company maintenance people were excellent, not all of them are. We went through 2 or 3 oil companies in 9 years. And whenever we had someone show up to annually service the system who just wanted to get to his next job, we ended up with no heat, or a clogged nozzle, or some other problem. Usually in the middle of the night on a holiday weekend with unusually cold weather. Now my old system was 20 years old and rather complicated with the 3 furnaces (2 for air, one for water) and a cold external chimney so it was probably not the easiest system to maintain. Modern systems do not work this way; I think mostly people with oil have boilers with circulating hot water coils to heat air or water in holding tanks.
The new GSHP system is expected to cost a lot less to run and emit a lot less carbon dioxide. I am looking forward to the winter so we can obtain data on that fact.
Oil is dirty and smelly. While some of the oil company maintenance people were excellent, not all of them are. We went through 2 or 3 oil companies in 9 years. And whenever we had someone show up to annually service the system who just wanted to get to his next job, we ended up with no heat, or a clogged nozzle, or some other problem. Usually in the middle of the night on a holiday weekend with unusually cold weather. Now my old system was 20 years old and rather complicated with the 3 furnaces (2 for air, one for water) and a cold external chimney so it was probably not the easiest system to maintain. Modern systems do not work this way; I think mostly people with oil have boilers with circulating hot water coils to heat air or water in holding tanks.
The new GSHP system is expected to cost a lot less to run and emit a lot less carbon dioxide. I am looking forward to the winter so we can obtain data on that fact.
Condensation pumps: water freezes in winter!
Both the GSHP and the ASHP water heater generate condensation. In the summer, like any air conditioner, the GSHP produces condensation that must be dumped somewhere. I don't have floor drains in my basement, so I have two choices: basement sink or outside the house. We had planned to run the output of the condensation pump outside like it had been for the old system. Then one of the astute people working on the project realized that my ASHP might generate condensation year round -- in which case it could not be vented outside else it would freeze!! Apparently they've seen that happen a few times. While we had hoped to use one condensation pump, because of the locations of the GSHP, the ASHP, and my basement sink, we ended up getting a second condensation pump and we'll run both of those in to the basement sink.
Minor setback
The project was going really well. As I explained in my last post, the trenching and piping were completed. All the remaining work was to be inside. Mostly in the basement for the GSHP but also in the attic (for the energy recovery ventilator (ERV). Lots of wire pulling, circuit running, plumbing, piping, ducting and insulation was occurring. We were expecting to fill the pipes with the water and propylene glycol solution and start the system up last Thursday. Then, last Wedesday, we had a bit of a setback.
I don't want to go in to the details because the party responsible for the accident has so far handled things quite professionally and the project will only be delayed about 3-5 days (depending on how you count). Accidents happen. All that you can hope for is that people take responsibility when they happen. And so far so good. No one was hurt. We just lost a little time. I joked that the project was going too smoothly.
So we are looking forward to Monday or Tuesday for power-on! Thermostats wires are in place, but no thermostats are connected yet. The ERV switches in the bathrooms are in place and the plug was installed in the attic, but the ERV needs a few more low-voltage connections before it is operational. Plugs are in place for the condensation pumps, but we need to run the condensation pump drains. The internal ground loop pipes still need some insulation and glycol... The electrician must make his final visit to make the 3 high voltage connections (circulation pump, GSHP and aux-heat). And then we can try it out!
I don't want to go in to the details because the party responsible for the accident has so far handled things quite professionally and the project will only be delayed about 3-5 days (depending on how you count). Accidents happen. All that you can hope for is that people take responsibility when they happen. And so far so good. No one was hurt. We just lost a little time. I joked that the project was going too smoothly.
So we are looking forward to Monday or Tuesday for power-on! Thermostats wires are in place, but no thermostats are connected yet. The ERV switches in the bathrooms are in place and the plug was installed in the attic, but the ERV needs a few more low-voltage connections before it is operational. Plugs are in place for the condensation pumps, but we need to run the condensation pump drains. The internal ground loop pipes still need some insulation and glycol... The electrician must make his final visit to make the 3 high voltage connections (circulation pump, GSHP and aux-heat). And then we can try it out!
Trenching & Piping
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| The supply line is on the right, with the T connection to the East hole |
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| Both returns run from the far hole to balance the flow. |
They used a hot-plate like device to heat the HDPE pipes to 500 degrees to join them together.
They used a torch to cut the pipe casings 4 feet below grade. But before they cut the casings, they inserted another metal pipe in to the casing to protect the HDPE tubes.
They ran both the returns from the farther hole to balance the flow between the holes. They also used different pipe diameters to balance the flow.
They put a rubber gasket around the top of the pipe casing to protect the HDPE pipes.
The picture on the right shows how they used a great big cork-screw drill to bore the 2 holes in the side of the foundation.
Once everything was connected, they flushed the tubes and performed a pressure test. Using water from my irrigation system, they filled the pipes, drained the air and pressurized the pipes to 90 PSI (lower right). It was a little unnerving to watch it steadily dropping to 72 PSI. They said that was expected because of the expansion of the tubes.
Surprise discovery #1: I have the rockiest lawn they've ever encountered. They dug up so many boulders they filled their dump truck and have to visit again to collect a few more.
Surprise discovery #2: a second unexpected pipe for the lawn irrigation system. This one with electricity attached. The irrigation company will visit on Monday to reconnect those wires. The trenching team reconnected the two pipes that they cut.
Thursday, August 12, 2010
Totally Tubular
Quick update today. The drilling company installed the tubes and thermal grout in to the 290-foot-deep bore holes. The tubes will hold a water and propylene glycol solution that will be the heat transfer medium for the ground source heat pump. It only took a couple of hours. You can see in the photo on the right a clever little jig they attached to the casing to help guide the tubes in to the hole. The tube is U-shaped and was pressure tested before they inserted it in to the well. On site, I believe they had to fill the tube with water before they could sink it in to the hole.
The big surprise to me was the thermal grout. The thermal grout is supposed to help the tubes make a good thermal connection with the ground. They used a substance called Therm-Ex. It is supposed to remain soft and flexible so that the tubes can expand and contract as they change temperature. Some how I imagined (incorrectly) that it would be more like a rigid cement.
When they pumped in the thermal grout, the water that had accumulated in the hole poured out. Now I realize why the last crew (the drilling crew), just before they left, dug a small pit and trenches to that pit. They were planning ahead for the pipe-and-grout crew. It was impressive forethought based on their experience. The pit kept the water spillage contained nicely.Tomorrow the third and final outside crew comes to excavate a trench 4-feet down between the holes and then on to the foundation. They'll bore 2 holes in to the foundation. The two U-pipes will be connected in parallel and the connecting pipes will get inserted in to the basement. They run the pipes 4-feet down to use the ground as insulation for the water in the tubes.
Wednesday, August 11, 2010
We're in really in hot water now!
Well, not quite "in" hot water. We just have hot water again. Today was a great day for the project. Yesterday we ripped out the old oil furnaces and disabled the oil-fired hot water heater. We had 50 gallons of warm water in the tank which was enough to get us through to the morning. Today the plumber and electrician visited.
Here's James from Kirkland and Shaw posing with his plumbing handiwork. On the left is James. In the middle is the GE Geospring air-source heat pump (ASHP) 50-gallon water heater. On the right is a 40-gallon electric water heater. The 40-gallon water heater is not connected electrically. It is just a holding tank for hot water from the desuperheater in the ground-source heat pump (not shown, not delivered yet). Between the two tanks is a mixing valve to make sure we don't put water that is too hot into the Geospring.
Our electrician, Gallant Electric, also was on-site today to install the subpanel that will provide power to the water heater, GSHP and auxiliary heat (and the condensation pump). They pulled a big armored cable from the main service panel to the new subpanel. They also installed the TED devices! (I'll get a picture of Andy when he returns next week).
The TED devices measure the power used by the main electrical panel and the subpanel. The subpanel is dedicated to the water heater and the HVAC system. The TEDs transmit their measurement data on the power lines. A device called a gateway plugs in to a normal electrical outlet and also gets connects to my Ethernet wires. The gateway is *really* cool. It basically has a little web browser inside. It can also transmit data to the google power meter so now I'm able to read my power measurements from my igoogle web page (see picture on the right).
The TED's have a really cool web interface as well (picture, right). It shows the power (kW) that my system is currently using, the cost of electricity or the pounds of carbon dioxide emitted to produce that electricity. It also has a cool graphing feature and can export the data.
The big dial in the center of the picture shows that at the moment we are using 2.7kW of electrical power. The bar in the middle of the left hand side shows that we've used 1.6kWh of electrical energy since we turned the TEDs on. That includes heating 50 gallons of water and cooking dinner this evening. If I click on the "$" it shows that we spent $0.28 on electricity today. The box in the upper right (if you could read it) says that the peak usage today was 5.7kW at 6:19PM (when corresponds to when we were cooking dinner).
The TEDs will allow me to measure the electricity use for the whole house and specifically for the GSHP and water heater. This will help us more deeply understand how much energy the new system is using. The graph at the right shows 3 bars per hour. The leftmost 2 bars (purple and green) in each group are the total power used by the house. The light blue bar (rightmost in each group) shows the power used by the Geospring. When we turned it on we were heating the 50 gallons up to 120 degrees for the first time using a combination of electrical resistance heat and the air-source heat pump. Once the water reached 120, I put the Geospring in "eheat" mode where it tries to avoid using the electrical resistance heat and relies more on the ASHP. The GSHP will be included in the light blue bar when it is installed.
Tomorrow we get the glycol circulation tubes and thermal grout installed in the two 290-foot holes we bored last week.
Here's James from Kirkland and Shaw posing with his plumbing handiwork. On the left is James. In the middle is the GE Geospring air-source heat pump (ASHP) 50-gallon water heater. On the right is a 40-gallon electric water heater. The 40-gallon water heater is not connected electrically. It is just a holding tank for hot water from the desuperheater in the ground-source heat pump (not shown, not delivered yet). Between the two tanks is a mixing valve to make sure we don't put water that is too hot into the Geospring.
Our electrician, Gallant Electric, also was on-site today to install the subpanel that will provide power to the water heater, GSHP and auxiliary heat (and the condensation pump). They pulled a big armored cable from the main service panel to the new subpanel. They also installed the TED devices! (I'll get a picture of Andy when he returns next week).
The TED devices measure the power used by the main electrical panel and the subpanel. The subpanel is dedicated to the water heater and the HVAC system. The TEDs transmit their measurement data on the power lines. A device called a gateway plugs in to a normal electrical outlet and also gets connects to my Ethernet wires. The gateway is *really* cool. It basically has a little web browser inside. It can also transmit data to the google power meter so now I'm able to read my power measurements from my igoogle web page (see picture on the right).
The TED's have a really cool web interface as well (picture, right). It shows the power (kW) that my system is currently using, the cost of electricity or the pounds of carbon dioxide emitted to produce that electricity. It also has a cool graphing feature and can export the data.
The big dial in the center of the picture shows that at the moment we are using 2.7kW of electrical power. The bar in the middle of the left hand side shows that we've used 1.6kWh of electrical energy since we turned the TEDs on. That includes heating 50 gallons of water and cooking dinner this evening. If I click on the "$" it shows that we spent $0.28 on electricity today. The box in the upper right (if you could read it) says that the peak usage today was 5.7kW at 6:19PM (when corresponds to when we were cooking dinner).
The TEDs will allow me to measure the electricity use for the whole house and specifically for the GSHP and water heater. This will help us more deeply understand how much energy the new system is using. The graph at the right shows 3 bars per hour. The leftmost 2 bars (purple and green) in each group are the total power used by the house. The light blue bar (rightmost in each group) shows the power used by the Geospring. When we turned it on we were heating the 50 gallons up to 120 degrees for the first time using a combination of electrical resistance heat and the air-source heat pump. Once the water reached 120, I put the Geospring in "eheat" mode where it tries to avoid using the electrical resistance heat and relies more on the ASHP. The GSHP will be included in the light blue bar when it is installed.
Tomorrow we get the glycol circulation tubes and thermal grout installed in the two 290-foot holes we bored last week.
Tuesday, August 10, 2010
Demolition!
On a day where the temperature peaked at 91 degrees, my GSHP installer ripped out the old heating and air conditioning system. They pumped down the refrigerant. They drained down and ripped out the oil lines. They cemented up the opening in my chimney flue.
They spent a fair bit of time fishing wires for one of the new thermostats. I'm thinking they should just sell wireless thermostats; They cost more than wired ones but it has got to be a net savings in installation labor.
After they left this evening, we painted the interior of foundation walls of the basement that had been blocked by the old system to match the rest of the basement. Most of it will be covered by new duct work and new equipment but it looks a lot nicer this way and was much easier to paint.
I also patched up the holes where the refrigerant lines were running through the sill. To do that, I wanted to cut some circular pieces of wood to fit in to the holes. I have a hole-saw of the required diameter. A hole saw is basically a cylindrical drill bit that cuts out circles, in my case 1.5 inches in diameter. Some hole saws have a center drill bit to stabilize the drill while you are cutting the hole. My hole saw does not and that makes starting the hole really tricky. The drill wants to dance around at first. A few years ago for another project I managed to do it but it was really difficult to get the hole saw going. Recently, while channel surfing one night, I saw an episode of This Old House where they made a simple jig for the hole saw to keep it from dancing around. I used a couple of pieces of scrap wood as guides and made a V-shaped groove wide enough for the hole-saw! I was done in just a few minutes.
Next up are the plumber and electrician. The final phase of out door work begins later this week when they install the tubes in the holes they drilled and thermal grout to keep it in place. After that they trench a path to the house and bore two holes in the foundation for those pipes. With any luck, the system will be up and running by the middle of next week.
They spent a fair bit of time fishing wires for one of the new thermostats. I'm thinking they should just sell wireless thermostats; They cost more than wired ones but it has got to be a net savings in installation labor.
After they left this evening, we painted the interior of foundation walls of the basement that had been blocked by the old system to match the rest of the basement. Most of it will be covered by new duct work and new equipment but it looks a lot nicer this way and was much easier to paint.
I also patched up the holes where the refrigerant lines were running through the sill. To do that, I wanted to cut some circular pieces of wood to fit in to the holes. I have a hole-saw of the required diameter. A hole saw is basically a cylindrical drill bit that cuts out circles, in my case 1.5 inches in diameter. Some hole saws have a center drill bit to stabilize the drill while you are cutting the hole. My hole saw does not and that makes starting the hole really tricky. The drill wants to dance around at first. A few years ago for another project I managed to do it but it was really difficult to get the hole saw going. Recently, while channel surfing one night, I saw an episode of This Old House where they made a simple jig for the hole saw to keep it from dancing around. I used a couple of pieces of scrap wood as guides and made a V-shaped groove wide enough for the hole-saw! I was done in just a few minutes.
Next up are the plumber and electrician. The final phase of out door work begins later this week when they install the tubes in the holes they drilled and thermal grout to keep it in place. After that they trench a path to the house and bore two holes in the foundation for those pipes. With any luck, the system will be up and running by the middle of next week.
Monday, August 9, 2010
Oh yeah, right, drilling uses energy too.
The drillers finished up on Saturday afternoon. They left the rig in place over the weekend with the 15 20-ft extension poles and the auger in the bore hole. The front of the truck was jacked up because of the hill on my front lawn. It drew some really funny looks from people driving by. It sort of looked like the truck was flying through the air especially if you could not see the single support post in the front of the truck.
I was talking to the drillers. Nice guys. Their 73,000 pound drilling rig can use about 200 gallons of diesel fuel per day. My project probably used about 300 gallons of fuel. I'll have to factor that in to the carbon dioxide equation. 300 gallons of heating oil can get me through a big chunk of a New England winter.
Saturday, August 7, 2010
Geology
The USGS has a really nice collection of geology maps for google earth. According to the map, my house sits on a combination of two types of igneous rocks: Diorite and Gabbro. Wikipedia states that "Diorite is an extremely hard rock, making it difficult to carve and work with. It is so hard that ancient civilizations (such as Ancient Egypt) used diorite balls to work granite."
Friday, August 6, 2010
Drill, baby, drill! (But in the good way!)
Day one of drilling for the ground source heat pump. The plans call for two 286-foot deep holes, 6-inches in diameter, 20-feet apart on the north side of my house. Given all the boulders sticking up out of my lawn, the driller anticipated hitting bedrock at a relatively shallow depth. Instead we were surprised that we didn't hit bedrock until 43-feet down! So it was slow going drilling through the clay and boulders that were encountered above the bedrock. Turns out that they like drilling through solid rock as they don't have to worry about stabilizing the bore hole with casings. Once they hit the bedrock, they say that they can often bore 100-feet per hour. With the midday start and the unexpected clay, they were only able to drill 140-feet today.
We asked them to stop at 6PM so my neighbors could enjoy their dinner in peace. The drillers are actually coming back on the weekend to finish the remaining drilling work! Hard workers!When drilling through the clay, they circulated water from a small pit they excavated next to the drilling rig. I assume that was both to remove the cuttings from the bore hole and to cool the drill bit.
As you can see from the photos on the right they had to raise the rig in the vicinity of a nice old silver maple. They had to prune a number of small branches. They actually tilted the truck while raising the drilling platform to avoid having to cut some branches. I have to admit I was pretty nervous about the whole process but I'm feeling much better now that they have gotten started and that they didn't find anything completely ridiculous (yet). I am optimistic that they'll be able to complete the two bore holes tomorrow. And we'll be able to keep our schedule for next week!
After drilling, what's next?
- Insert the water pipes in the bore holes
- Pump in the thermal grout to stabilize the pipes in the bore holes and make a good thermal connection to the ground.
- Remove the refrigerant in the A/C system and remove the compressor/condensers
- Trench a path the foundation
- Bore holes in the foundation for the pipes
- Drain my oil lines
- Demolish/remove the old HVAC system and water heater
- Install the new water heater, holding tank and lots of piping
- Install the electrical circuits for the GSHP and the water heater.
- Finally install the flow center and GSHP!
Saturday, July 31, 2010
Questions about GSHP systems
As we get closer to the installation I find myself talking to more and more people about ground source heat pumps and how they work. There is a lot of stuff out there on the web that describes it and it can get rather complicated. I'm reading all I can but I am not to the point where I can explain it succinctly. I found this very high level description from a source in Canada. I am still looking for a good one that will help me explain this all very clearly.
The other question I get is how popular are GSHP systems? According to the wikipedia article on GSHP systems, there were "As of 2004, over a million systems installed worldwide" and "Each year, about 80,000 units are installed in the USA".
Another important question is "how much does it cost?" Sadly, it seems like a lot. Last year, I was faced with estimates of $16,000 to replace my 20-year-old oil-fired systems with a modern boiler and circulating water coil (hydronics). This GSHP system costs more. On the surface it appears to be a lot more but three things help mitigate that cost. One is that 30% of the system cost gets rebated from the federal government at tax time. For the water heater (the Geospring ASHP) the limit of that is $1500, but there is no limit on the rebate for the GSHP system. That brings the total system cost much closer but still well north of the new oil system estimates. The second thing that helps is that we were able to get a $15,000 zero-percent 5-year loan after getting a home energy assessment from mass-save. (They even gave us some cool new CFL light bulbs which achieve their full brightness much more quickly than the bulbs that I purchased a couple of years ago.) Still it'll cost more to install the GSHP. The operating costs are expected to be much lower than my current system and also lower than a modern oil system + conventional A/C. We expect it to cost about $5000 more after full installation. And one must factor in the $15K interest free loan that I can pay out over the next 5 years.
The other issue with the oil-system upgrade (that we chose not to do) was that I'd have to consider getting my old chimney lined to accommodate the higher efficiency of the hypothetical new oil boiler. We had a quote for about $3000 to do that and it involved removing some bricks to get at a jog in the flue. That was not included in the $16000 estimate.
And for me, best of all is no more oil-system maintenance issues.
So what's next?
We expect the drilling to begin this week. After the drilling, they have to install the pipes in to the 2 6-inch holes and fill them with a thermal grout. Then they excavate a trench from the holes to the house and bore holes in the foundation about 4 feet underground so that the pipes can be connected to the heat pump in my basement.
When they get to excavating for the foundation bore holes, because of the location, my installer will have to remove my existing A/C system condensers pumping down the refrigerant and disposing of it responsibly. Then we'll be without A/C for a while until the new system is going. Hopefully it won't be too long given how hot it has been lately...
When the air conditioners are removed from service I will get my electrician to wire the new electrical circuits and the plumber to hook up my Geospring water heater and holding tank. Can't wait!
Today, I flagged the in-ground sprinkler heads with the hope that the drilling rig and excavator can avoid destroying the ones they must traverse to get to the work area. We also had a couple of tree branches trimmed so that the drilling rig can get in to the work area next to my house.
The other question I get is how popular are GSHP systems? According to the wikipedia article on GSHP systems, there were "As of 2004, over a million systems installed worldwide" and "Each year, about 80,000 units are installed in the USA".
Another important question is "how much does it cost?" Sadly, it seems like a lot. Last year, I was faced with estimates of $16,000 to replace my 20-year-old oil-fired systems with a modern boiler and circulating water coil (hydronics). This GSHP system costs more. On the surface it appears to be a lot more but three things help mitigate that cost. One is that 30% of the system cost gets rebated from the federal government at tax time. For the water heater (the Geospring ASHP) the limit of that is $1500, but there is no limit on the rebate for the GSHP system. That brings the total system cost much closer but still well north of the new oil system estimates. The second thing that helps is that we were able to get a $15,000 zero-percent 5-year loan after getting a home energy assessment from mass-save. (They even gave us some cool new CFL light bulbs which achieve their full brightness much more quickly than the bulbs that I purchased a couple of years ago.) Still it'll cost more to install the GSHP. The operating costs are expected to be much lower than my current system and also lower than a modern oil system + conventional A/C. We expect it to cost about $5000 more after full installation. And one must factor in the $15K interest free loan that I can pay out over the next 5 years.
The other issue with the oil-system upgrade (that we chose not to do) was that I'd have to consider getting my old chimney lined to accommodate the higher efficiency of the hypothetical new oil boiler. We had a quote for about $3000 to do that and it involved removing some bricks to get at a jog in the flue. That was not included in the $16000 estimate.
And for me, best of all is no more oil-system maintenance issues.
So what's next?
We expect the drilling to begin this week. After the drilling, they have to install the pipes in to the 2 6-inch holes and fill them with a thermal grout. Then they excavate a trench from the holes to the house and bore holes in the foundation about 4 feet underground so that the pipes can be connected to the heat pump in my basement.
When they get to excavating for the foundation bore holes, because of the location, my installer will have to remove my existing A/C system condensers pumping down the refrigerant and disposing of it responsibly. Then we'll be without A/C for a while until the new system is going. Hopefully it won't be too long given how hot it has been lately...
When the air conditioners are removed from service I will get my electrician to wire the new electrical circuits and the plumber to hook up my Geospring water heater and holding tank. Can't wait!
Today, I flagged the in-ground sprinkler heads with the hope that the drilling rig and excavator can avoid destroying the ones they must traverse to get to the work area. We also had a couple of tree branches trimmed so that the drilling rig can get in to the work area next to my house.
Tuesday, July 20, 2010
Geospring's little quirk
The GE Geospring hybrid air-source heat pump has a little quirk according to the manufacturer. If the input water is above the set point for the water heater (say 120 degrees F), then the water heater experiences what they call "run-away" heating and presumably destroys itself. This is important for people to know especially if they are hooking the geospring to a desuperheater! I guess this could be an issue too if people are warming water with solar water heaters in conjunction with the geospring.
The desuperheater takes cold water from the supply line, heats it up when the GSHP is running, and dumps hot water back in to the drain plug of the water heater. On my GSHP, the desuperheater can be configured to output hot water at either 150 degrees or 125 degrees.
To avoid the bug in the geospring, we are going to put a mixing valve in the pipe coming from the desuperheater in the ground source heat pump. The mixing valve is pretty simple. It is 3-connection device with a configurable temperature setting. It mixes cold water in with the hot water if the hot water is above the temperature setting on the mixing valve.
The desuperheater takes cold water from the supply line, heats it up when the GSHP is running, and dumps hot water back in to the drain plug of the water heater. On my GSHP, the desuperheater can be configured to output hot water at either 150 degrees or 125 degrees.
To avoid the bug in the geospring, we are going to put a mixing valve in the pipe coming from the desuperheater in the ground source heat pump. The mixing valve is pretty simple. It is 3-connection device with a configurable temperature setting. It mixes cold water in with the hot water if the hot water is above the temperature setting on the mixing valve.
Friday, July 16, 2010
Upgrading the heating system for my home
It is time to upgrade my home's 20-year-old heating system. It seems like a bit of an adventure but after the maintenance problems we experienced last spring, we really felt that we had to do something to improve the situation.
Current situation
My house is not very large, about 2300 square feet, and is fairly well insulated. I had an infrared scan and a blower door test a couple of years ago and the number one recommendation was that I get my heating system upgraded. A few other simple suggestions resulted from those tests, adding insulation in my attic, sealing the attic hatch more tightly, adding insulation in a couple of places that were leaky.
My house has a forced hot air system. Actually, it has two complete oil-fired furnaces for heating the air. One for upstairs and one for downstairs. I also currently have a third oil-fired water heater. It is direct fired, has its own burner. So my chimney has three exhaust sources all joined together and entering the chimney.
I asked the HVAC contractor who was involved in the building of my house why he did it this way. He said that if they had used one unit the A/C would have been too big and cycled even more quickly than the system I have now which -- in my humble opinion -- cycles too quickly already.
My chimney is external to the house and the flue is big - big enough to handle the emissions from the 3 furnaces all going at the same time. Think about all that cold air in the chimney. Since my house is relatively tight, I don't use a lot of heat. So the chimney is often pretty cold. So I have bad draft on the chimney. A few years ago, we installed a draft inducer. That is a fan that kicks in whenever any of the 3 furnaces is combusting oil. I never liked the draft inducer. It was really noisy and sucked a lot of air out of the house to create the draft in the chimney. To get enough air for the furnaces and the draft inducer, my HVAC guys cut two holes in the side of my house to get combustion air. This results in the basement being even more humid in the summer than it otherwise would be. So I run a dehumidifer to dehumidify my little portion of planet Earth, I guess. This year, as part of my maintenance nightmare, my oil company replaced the draft inducer.
Each one of the furnaces for the hot air is probably big enough to heat the whole house on its own. 87K BTU each. In the heating season, they cycle too quickly so that means they are inefficient and wasting oil. In the cooling season, they also cycle too quickly. I have a 2.5 ton condenser for the 1st floor and a 2 ton condenser for the 2nd floor. Because they cycle too quickly, they don't get the moisture out of the house. In both seasons, because of the oversized heating and cooling, the air often feels stale in the house. The new system should remedy this as well.
Bathroom Ventilation
One more ventilation related thing: my bathroom showers each have fans that take the moist air out of the shower and in to my attic where it vents in to the soffit! That is never a good idea. When I first noticed this, I decided we had to stop using the bathroom fans. The air flow in the attic is supposed to go in the soffit vents, not out of it! The air flows up the sheathing and out the ridge vent. So that moist air was not leaving my house, it was staying inside the attic. We are fixing this problem too. As part of my heating system upgrade, we're installing an ERV - an energy recovery ventilator. No more opening the bathroom windows all winter long! More on that later.
The New System
The new system will be a Ground Source Heat Pump (GSHP) for heating my air and an Air Source Heat Pump (ASHP) for heating my hot water (more about the ASHP later). Sometimes people say "geothermal" but I think that term is more for places like Iceland. A GSHP relies on heat exchange with the ground, which in my case is expected to be 50 degrees Fahrenheit year round at a depth of greath than 10 feet. The system calls for 2 6-inch holes about 300 feet each, 20 feet apart. A loop of tubing will run from the GSHP in my basement down in to each of those holes and back up in to the house. In winter we extract heat from the ground by pumping 30 degree fluid through a closed loop and heating it to 50 degrees. In the summer we dump heat in to the ground from my house by taking the warm house air and circulating it through that same closed loop tube.
There is an interesting feature on the GSHP called a desuperheater which will help heat the hot water mostly in the summer, and only when the A/C is running. We are also installing an energy recovery ventilator (ERV) to provide fresh air in to the air duct returns while reclaiming the heat that is in the air coming out of the shower fans.
Electricity
We're basically going to be using more electricity but will have no more visits from the oil company. I'm going to measure our electricity use more closely. To do that, I purchased a "TED" http://www.theenergydetective.com/ . I got the 5002 model so that I can put one measuring device on my main electrical service panel and one on the subpanel for the HVAC+H2O system. The TED works with the Google Power Meter. It transmits data about my power use on the electrical wires and another device picks that data up an transmits it over my home's ethernet wiring.
In Massachusetts most of our electricity comes from burning coal. My electric utility has an option to purchase energy from a wind farm for a few extra cents per kWh. One can purchase 50% or 100% of your energy from wind. I know that is just net energy entering the grid and my electricity is probably coming from coal, but I believe paying these extra few cents encourages more investment in wind energy and that is a good thing. Obviously it would be nice if we had more government subsidies for wind and solar and other renewable energy resources.
I was a little concerned that the house might not have enough electrical current to support the new equipment. One electrician did a load calculation and thought it would be close and gave me very expensive options for upgrading my current 200Amp service. (Electrical load calculations are rather interesting; maybe a topic for another day). Another electrician that I've used several times before and who has a good reputation locally thought that there would be absolutely no problem. I guess we'll find out once the TED starts reporting its data.
The big question in all of this is the auxillary electrical resistive heating. That aux heat uses a lot of electrical current and as a result is very expensive. The GSHP includes this auxillary heating option for when the external temperature is outside of the GSHP design's operating range and as a result it cannot keep up the internal temperature of the house. The aux heat is like emergency backup heat. The GSHP controls/settings use the electrical resistive heat when it cannot reach the programmed temperature at the desired time. I haven't seen how the controls work yet. One person I spoke with disabled his aux heat entirely. Another person that I spoke with set the controls so that it only uses the aux heat in really extreme conditions. The whole system is designed to keep the house warmer than we normally keep the house (in case we ever want to sell it to people who don't enjoy wearing sweaters). Maybe it won't get used that much. We'll see ...
Air source heat pump
The ASHP for heating the water is probably the most mundane part of the system. I'm using the GE Geospring hybrid water heater. This water heater claims to have an energy factor (EF) of 2.3. The energy factor of 2.3 means that for every unit of electrical energy I use, I get 2.3 units of energy for heating the water. It works by taking heat energy out of the air (from my basement) and using that to heat the water in the tank. Depending on various modes, it can also use electrical resistive heat to heat the water if there are demand spikes and the ASHP cannot replenish the hot water fast enough. The ASHP will also dehumidify my basement as a side effect of its normal activity.
For the first concern: Electrical resistive heating is pretty expensive. Not sure what to say about the eletrical resistive heating. My hope is that it won't get used. I'm going to measure and hopefully it'll work out. The desuperheater will help a little. And if it is really bad, I might consider doing some solar water heating.
For the basement temperature issue, recall that I mentioned that I have two combustion air holes in the side of my house. Well those probably have a much bigger effect of the temperature of my basement than the ASHP will be. I might even be ahead now that I can close off those combustion air vents.
In future posts I hope to talk more about all these things. We have lots of things to do in the next few weeks. Some tree branches need to be cut to make room for the drilling rig. I have to get the old oil system removed and also remove the oil from my 2 oil tanks. The only access to my property for the drilling rig (a big truck) is by traversing part of my neighbor's front lawn. So I am indebted to my neighbor for their allowing this access and their willingness to tolerate the damage that the rig and excavator will inevitably incur. The driller has a plan to minimize the damage. Stay tuned...
Current situation
My house is not very large, about 2300 square feet, and is fairly well insulated. I had an infrared scan and a blower door test a couple of years ago and the number one recommendation was that I get my heating system upgraded. A few other simple suggestions resulted from those tests, adding insulation in my attic, sealing the attic hatch more tightly, adding insulation in a couple of places that were leaky.
My house has a forced hot air system. Actually, it has two complete oil-fired furnaces for heating the air. One for upstairs and one for downstairs. I also currently have a third oil-fired water heater. It is direct fired, has its own burner. So my chimney has three exhaust sources all joined together and entering the chimney.I asked the HVAC contractor who was involved in the building of my house why he did it this way. He said that if they had used one unit the A/C would have been too big and cycled even more quickly than the system I have now which -- in my humble opinion -- cycles too quickly already.
I explored upgrading my existing oil heating system to a more modern one that uses a single boiler and a set of water coils that could run to each of the 2 air handlers and to the water holding tank. The estimates I got for that were lower than the cost of my current system. But I am tired of the oil furnace maintenance routine. I've had several different oil companies over the years and it was always hard to get them to do all the required maintenance. Seems like they'd have some good guys who did great work and some guys who just wanted to get in and out as fast as they could. The latter usually resulted in clogged heat exchangers, clogged nozzles, etc.
My chimney is external to the house and the flue is big - big enough to handle the emissions from the 3 furnaces all going at the same time. Think about all that cold air in the chimney. Since my house is relatively tight, I don't use a lot of heat. So the chimney is often pretty cold. So I have bad draft on the chimney. A few years ago, we installed a draft inducer. That is a fan that kicks in whenever any of the 3 furnaces is combusting oil. I never liked the draft inducer. It was really noisy and sucked a lot of air out of the house to create the draft in the chimney. To get enough air for the furnaces and the draft inducer, my HVAC guys cut two holes in the side of my house to get combustion air. This results in the basement being even more humid in the summer than it otherwise would be. So I run a dehumidifer to dehumidify my little portion of planet Earth, I guess. This year, as part of my maintenance nightmare, my oil company replaced the draft inducer.
Each one of the furnaces for the hot air is probably big enough to heat the whole house on its own. 87K BTU each. In the heating season, they cycle too quickly so that means they are inefficient and wasting oil. In the cooling season, they also cycle too quickly. I have a 2.5 ton condenser for the 1st floor and a 2 ton condenser for the 2nd floor. Because they cycle too quickly, they don't get the moisture out of the house. In both seasons, because of the oversized heating and cooling, the air often feels stale in the house. The new system should remedy this as well.Bathroom Ventilation
One more ventilation related thing: my bathroom showers each have fans that take the moist air out of the shower and in to my attic where it vents in to the soffit! That is never a good idea. When I first noticed this, I decided we had to stop using the bathroom fans. The air flow in the attic is supposed to go in the soffit vents, not out of it! The air flows up the sheathing and out the ridge vent. So that moist air was not leaving my house, it was staying inside the attic. We are fixing this problem too. As part of my heating system upgrade, we're installing an ERV - an energy recovery ventilator. No more opening the bathroom windows all winter long! More on that later.
The New System
The new system will be a Ground Source Heat Pump (GSHP) for heating my air and an Air Source Heat Pump (ASHP) for heating my hot water (more about the ASHP later). Sometimes people say "geothermal" but I think that term is more for places like Iceland. A GSHP relies on heat exchange with the ground, which in my case is expected to be 50 degrees Fahrenheit year round at a depth of greath than 10 feet. The system calls for 2 6-inch holes about 300 feet each, 20 feet apart. A loop of tubing will run from the GSHP in my basement down in to each of those holes and back up in to the house. In winter we extract heat from the ground by pumping 30 degree fluid through a closed loop and heating it to 50 degrees. In the summer we dump heat in to the ground from my house by taking the warm house air and circulating it through that same closed loop tube.
There is an interesting feature on the GSHP called a desuperheater which will help heat the hot water mostly in the summer, and only when the A/C is running. We are also installing an energy recovery ventilator (ERV) to provide fresh air in to the air duct returns while reclaiming the heat that is in the air coming out of the shower fans.
We don't have the option of "natural" gas where I live. The gas lines don't reach near my house. Currently natural gas with a modern furnace seems like it would be hard to argue with cost-wise. But it is a fossil fuel... (I always giggle when I think about the term "natural" gas. What a clever marketing term! Who doesn't love nature? ... Sigh.)
Electricity
We're basically going to be using more electricity but will have no more visits from the oil company. I'm going to measure our electricity use more closely. To do that, I purchased a "TED" http://www.theenergydetective.com/ . I got the 5002 model so that I can put one measuring device on my main electrical service panel and one on the subpanel for the HVAC+H2O system. The TED works with the Google Power Meter. It transmits data about my power use on the electrical wires and another device picks that data up an transmits it over my home's ethernet wiring.
In Massachusetts most of our electricity comes from burning coal. My electric utility has an option to purchase energy from a wind farm for a few extra cents per kWh. One can purchase 50% or 100% of your energy from wind. I know that is just net energy entering the grid and my electricity is probably coming from coal, but I believe paying these extra few cents encourages more investment in wind energy and that is a good thing. Obviously it would be nice if we had more government subsidies for wind and solar and other renewable energy resources.
I was a little concerned that the house might not have enough electrical current to support the new equipment. One electrician did a load calculation and thought it would be close and gave me very expensive options for upgrading my current 200Amp service. (Electrical load calculations are rather interesting; maybe a topic for another day). Another electrician that I've used several times before and who has a good reputation locally thought that there would be absolutely no problem. I guess we'll find out once the TED starts reporting its data.
The big question in all of this is the auxillary electrical resistive heating. That aux heat uses a lot of electrical current and as a result is very expensive. The GSHP includes this auxillary heating option for when the external temperature is outside of the GSHP design's operating range and as a result it cannot keep up the internal temperature of the house. The aux heat is like emergency backup heat. The GSHP controls/settings use the electrical resistive heat when it cannot reach the programmed temperature at the desired time. I haven't seen how the controls work yet. One person I spoke with disabled his aux heat entirely. Another person that I spoke with set the controls so that it only uses the aux heat in really extreme conditions. The whole system is designed to keep the house warmer than we normally keep the house (in case we ever want to sell it to people who don't enjoy wearing sweaters). Maybe it won't get used that much. We'll see ...
Air source heat pump
The ASHP for heating the water is probably the most mundane part of the system. I'm using the GE Geospring hybrid water heater. This water heater claims to have an energy factor (EF) of 2.3. The energy factor of 2.3 means that for every unit of electrical energy I use, I get 2.3 units of energy for heating the water. It works by taking heat energy out of the air (from my basement) and using that to heat the water in the tank. Depending on various modes, it can also use electrical resistive heat to heat the water if there are demand spikes and the ASHP cannot replenish the hot water fast enough. The ASHP will also dehumidify my basement as a side effect of its normal activity.
I also looked at a cool non-integrated ASHP called the North Road Geyser. It has an EF of 2.0 which is slightly less than the Geospring, but the nice thing about it is that it is a separate unit from the water holding tank. If the tank fails, I can buy a new inexpensive electric water heater and use the same old Geyser heat pump. The Geyser hooks in via two "T" connections at the drain of any existing electric water heater tank. That poses a problem for me: My house already has a passive recirculation system that hooks in to the drain. And there is the new connection from the desuperheater from the GSHP. I thought that would be too many connections at the drain of the water heater. The Geyser still looks like a really cool device though.The biggest concerns with the ASHP are that (a) it might resort to electrical heating too often and (b) is that it will lower the temperature of my basement.
For the first concern: Electrical resistive heating is pretty expensive. Not sure what to say about the eletrical resistive heating. My hope is that it won't get used. I'm going to measure and hopefully it'll work out. The desuperheater will help a little. And if it is really bad, I might consider doing some solar water heating.
Aside: The solar water heating systems I've found for that are more money than I want to spend right now -- even though solar water heating seems to make a lot more sense than solar photovoltaic right now. Although I have my eyes on the Dow Powerhouse solar shingles. They look really cool. Out later this year supposedly!
For the basement temperature issue, recall that I mentioned that I have two combustion air holes in the side of my house. Well those probably have a much bigger effect of the temperature of my basement than the ASHP will be. I might even be ahead now that I can close off those combustion air vents.
In future posts I hope to talk more about all these things. We have lots of things to do in the next few weeks. Some tree branches need to be cut to make room for the drilling rig. I have to get the old oil system removed and also remove the oil from my 2 oil tanks. The only access to my property for the drilling rig (a big truck) is by traversing part of my neighbor's front lawn. So I am indebted to my neighbor for their allowing this access and their willingness to tolerate the damage that the rig and excavator will inevitably incur. The driller has a plan to minimize the damage. Stay tuned...
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