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.

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!!

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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.

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.

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.

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!

Trenching & Piping

The supply line is on the right, with the T connection to the East hole

Both returns run from the far hole to balance the flow.

(This posting was delayed; I'll explain in my next post).  The drilling contractor finished the outside work. This final step was referred to "trenching". An medium size excavator and dump truck visited. The trench they dug was impressive. Much bigger than I imagined.  They hit so many rocks that they have to come back to remove more boulders and dirt.


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.

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.

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.

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.

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.

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."

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? 

1. Insert the water pipes in the bore holes
2. Pump in the thermal grout to stabilize the pipes in the bore holes and make a good thermal connection to the ground.
3. Remove the refrigerant in the A/C system and remove the compressor/condensers
4. Trench a path the foundation
5. Bore holes in the foundation for the pipes
6. Drain my oil lines
7. Demolish/remove the old HVAC system and water heater 
8. Install the new water heater, holding tank and lots of piping
9. Install the electrical circuits for the GSHP and the water heater. 
10. Finally install the flow center and GSHP! 

We expect to be without A/C from the 11th to around the 19th. Hope the heat wave is over for the moment!! Usually that is not a big deal, but this summer has been so ridiculously hot! Hopefully that is not the "new normal" on Eaarth.