The Homemade Heat Pump Manifesto

[AC_Hacker]

Originally Posted by superlen

At the time I was active there was only hvac-talk (OMG, that bunch will suck the superheat right out of your sails). Anyhow, Thanks.

Len

Len,

Welcome to the madhouse!

Yep, it was those very same superheat sucking charmers that convinced me that the doors needed to be flung wide open.

I'm very happy to say that the doors are definitely open and since this is the Internet, they're not going to close again. The cat is way out of the bag and ain't going back.

If you look around EcoRenovator, there are some excellent projects that have been carried through, and have been well documented for all to see.

If you have questions or problems or want to share progress, we're willing, wanting and waiting to hear and to help.

As always, keep your B.S. detector in working order. It may start beeping now and then.

But for the most part, we have an excellent, friendly pool of knowledge and hands-on lore.

Definitely a 'Can-Do' crew.

Best,

-AC_Hacker

[superlen]

AC, Thanks for the warm welcome.

I'll start collecting some pics of the system I'll be working on and the options I have. I have too many options and ideas (each with their own pros/cons) and I would love some feedback from the group on them.

I'll post a new thread in the future, but here are some basics of what I'm working with:

- 4200 sq ft (2200 main floor, 1000 2nd story, 1000 basement)
- wrapped in 6" of foam (r36 walls, r60 ceiling, low air leakage, half of basement is below grade)
- NW Arkansas moderate climate (4500 hdd)
- staple up radiant 1/2" o2 pex for 2200 sq ft main floor. (all parts bought, not installed yet - originally no spreader plates planned but that seems to be a hot topic here. )
- 140Kbtu wood boiler (not plumbed but set in place)
- fireplace insert (primary heat now & will keep the main floor comfortable)
- 70 acres of free wood.
- Artesian Spring 50ft from house ( 3gpm min (august), max 100'sgpm after hard rain - 55deg)
- 6000 gallon holding tank for spring
- access to multiple 350-500gallon tanks
- 150 ft well (used for swimming pool and vegetable garden - at one point would continually flow 15gpm indefinitely, but has some issues now and probably needs to be redeveloped)
- Abandoned 5 ton loop field 200ft from house. (5 parallel - 300ft loops of 3/4" pex )
- 2 acre pond 1000' from house.
- surplus 5T coaxial HX from GSHP I ran several years ago.(currently plumbed in as a desuperheater on the air conditioning condenser)
- several spare 4t and 5t compressors/ condensers/evaporators/txvs/ect.

My plan is to utilize the spring and/or the well as evaporator heat source for a WTW heat pump. The radiant floor would then be the heat sink for the evaporator.

Thats enough for now and I don't want to cloud up this thread.

Len

[AC_Hacker]

Originally Posted by superlen

AC, Thanks for the warm welcome.

I'll start collecting some pics of the system I'll be working on and the options I have. I have too many options and ideas (each with their own pros/cons) and I would love some feedback from the group on them.

I'll post a new thread in the future, but here are some basics of what I'm working with:

- 4200 sq ft (2200 main floor, 1000 2nd story, 1000 basement)
- wrapped in 6" of foam (r36 walls, r60 ceiling, low air leakage, half of basement is below grade)
- NW Arkansas moderate climate (4500 hdd)
- staple up radiant 1/2" o2 pex for 2200 sq ft main floor. (all parts bought, not installed yet - originally no spreader plates planned but that seems to be a hot topic here. )
- 140Kbtu wood boiler (not plumbed but set in place)
- fireplace insert (primary heat now & will keep the main floor comfortable)
- 70 acres of free wood.
- Artesian Spring 50ft from house ( 3gpm min (august), max 100'sgpm after hard rain - 55deg)
- 6000 gallon holding tank for spring
- access to multiple 350-500gallon tanks
- 150 ft well (used for swimming pool and vegetable garden - at one point would continually flow 15gpm indefinitely, but has some issues now and probably needs to be redeveloped)
- Abandoned 5 ton loop field 200ft from house. (5 parallel - 300ft loops of 3/4" pex )
- 2 acre pond 1000' from house.
- surplus 5T coaxial HX from GSHP I ran several years ago.(currently plumbed in as a desuperheater on the air conditioning condenser)
- several spare 4t and 5t compressors/ condensers/evaporators/txvs/ect.

My plan is to utilize the spring and/or the well as evaporator heat source for a WTW heat pump. The radiant floor would then be the heat sink for the evaporator.

Thats enough for now and I don't want to cloud up this thread.

Len

Sounds like you've lived in the house for a while. You spelled out a lot of info except what the heat load for the house is... which is the most important part.

Originally Posted by superlen

Abandoned 5 ton loop field 200ft from house. (5 parallel - 300ft loops of 3/4" pex )

WTF?!? Do you know anything about this?? From your specs, and not knowing the characteristics of how it was put in, or the potential of the soil in your area, it doesn't seen to me that you could get 5 Tons from such a layout. But even if it was not able to deliver 5 Tons, with the insulation you described, and a high efficiency floor, I wouldn't think 5 Tons should be required.

However if it is in good shape (a properly installed loop field should last hundreds of years) I would say that you should start there. You will not need to battle a constant invasion of particulates, for instance. Get it working, and then see what else is required.

Regarding your staple up floor... without plates, the only thing worse would be suspended tubes. Even with plates, there is a problem.

With the exception of the wood burning fireplace, all of the potential heat sources you cited, are in a class known as Low Temperature Heating Sources (=< 120F).

This means that they will not be able to reach the temperatures needed by a staple up PEX floor (180F). even if you put in lots of thin aluminum plates it might lower the feed temps (140-160F). But your Low Temperature sources will deliver lots of heat for cheap at a lower temperature (=< 120F).

If you totally bit the bullet, and built your radiant floor on top of your existing floor (spacing the PEX closer to maybe 6" to 8" AND STILL USING PLATES), then your Low Temperature Sources would thrive.

There's a lot of knowledge in the radiant heating industry, but not all of it has trickled down to the installers, who often double as designers, yet. Many of them are still designing floors for fossil fuel (=>180F) and then combining those designs with Low Temp Sources (=< 120F), and the result is gnashing of teeth and wailing in the outer darkness.

I'd also suggest that if you can get even more insulation into the attic, it would be money well spent.

And find out what the heat load (A/C & Heating) is of your house.

Best,

-AC

[superlen]

Originally Posted by AC_Hacker

Sounds like you've lived in the house for a while. You spelled out a lot of info except what the heat load for the house is... which is the most important part.

I ran a heat load back in 08 before my remodel & it was a little over 3T (39K heat loss) and (30k heat gain I seem to recall). I was estimating some at the time as my plans weren't 100% firm at that point. I was using Hvac-Calc (BTW, anyone reading, this is a pretty good piece of software, easy to use/figure out & plenty of features for most, but not so many that the UI gets confusing) I should run another now, but those numbers I think are pretty close. I need a blower door test to confirm my air change assumptions.

Originally Posted by AC_Hacker

WTF?!? Do you know anything about this?? From your specs, and not knowing the characteristics of how it was put in, or the potential of the soil in your area, it doesn't seen to me that you could get 5 Tons from such a layout. But even if it was not able to deliver 5 Tons, with the insulation you described, and a high efficiency floor, I wouldn't think 5 Tons should be required.

Sadly, yes. I installed it around 2002 time frame. From my research then I had determined that 300' per ton was appropriate....not sure if it really was but that's what I went with. It did keep the house cool with a lot lower electric bill, but I do think my loopfield was too small as I had to add more pumping power to flow more btus out than I had calculated. Note: At that time, the house was only 2200sq ft & was so poorly insulated and sealed that a standard 10seer 5t AC could barely keep up in mid-August. It was the perfect example of all worst case scenarios (leaky ducts, entire system in attic, loose 4" bats of insulation in ceiling, most duct insulation falling off, dropped ceiling in some parts of the house, ect ect.)

However if it is in good shape (a properly installed loop field should last hundreds of years) I would say that you should start there. You will not need to battle a constant invasion of particulates, for instance. Get it working, and then see what else is required.

When I installed the field, I used 1.25" pvc to connect the loop field to the house. The loops are 3/4" PEX, not pvc, just the supply/return are pvc. (wishful thinking I now know on my part) The field is 200' from the house. As one would expect, I got a leak after the third season. I would need to dig up and replace with appropriate pipe which isn't too big a deal. However, I have also since installed a swimming pool directly between the house and the field and I of course ripped out the supply/return through that area and I will have to reroute around the pool. It would probably mean 300' each of supply and return lines which is more pumping loss, but also 600' more total loop in the ground.

The main reason I would like to use the spring is mostly for my own entertainment & curiosity purposes. I just think it would fun to use it. The spring serves no other purpose currently. Perhaps it would be better to do a spring based hot water heater project (similar to Memphis' nifty DX) to satisfy my desire to use it for something and stick with a more conventional approach to the basic home heating/cooling.

I'll grab some pics this weekend.

Len

[superlen]

Thought I'd throw up a picture of the loop field & spring placement.

The yellow indicates the 5 - 300' 3/4" pex (150 out and back) loops. All are plumbed in parallel.

The Orange is the original 1.25" pvc supply/return.

The Pink would be the new path I would need to take for the supply/return.

The Dark Blue dot is the location of the spring. The light blue is the location of the well already plumbed into the house. Note: the well is just used for irrigation and pool top off. The house is connected to rural water.

What isn't apparent from the photo is that the whole property is on a hill side. The spring (blue dot) is about 30' lower than the house/driveway right by it. It's quite the dropoff along the drive at that point & installing a line down that hill side will be challenging although there are already several lines historically connecting the two. At one point (1915-1940) the outside spring box was plumbed into the basement of the house with another small spring box inside. The spring supplied the house until 1970 when the well was drilled. The house was on well water until 2001 when I bought the property.

Len

[AC_Hacker]

Good info here.

I do think that making heat (& cool) retention the top priority, before considering the implementation of your heat/cool source.

That approach brings many 'low temperature heating and high temperature cooling' scenarios into range.

I agree, Hvac-Calc is a really good program. Did you run your calcs before all the insulation you put in? If that's the case, you might want to re-do them.

Another thing to know, is how is your cooling distributed? I'd imagine that it is central air. Correct?

If that's the case, increasing air volumes will benefit a high temperature cooling approach.

Just as in low temperature heating, where you need to greatly increase the radiant area to get the heat that is lost from your house... in high temperature cooling, you need to increase air volumes, which may necessitate sizing your ducts larger.

Actually the whole industry is moving to high-efficiency, high-capacity, variable speed ECM fans.

There are also interesting implementations of radiant cooling in Europe. The radiant surfaces are built into the ceilings and are carefully monitored for dew point. The finding is that comfort can be achieved without reducing the sensible temperature as far as with convection.

From your photos, I can't see any power roof vents... are there any?

-AC

[superlen]

I did my calcs based on the R60 and R36 that I have now. Although the version of HVCALC I had wouldn't go to R36 for walls, so I used R18 and cut the surface area in half. I do need to redo the entire load calc, but I've been lazy. With three levels, some partially underground, it takes a bit to key in all the data properly. One thing I did find out about recently is that our local electrical utility will come do an energy audit for you (including blower door test) for $100. Others may want to check into that locally as well. I think that is $100 well spent, particularly if you are in the northern/colder climates.

Cooling is typical central air, all new ducts now inside the heat/cool envelope (nothing in the attic whatsoever). I had some limitations on duct routing that we had to get creative with, but I kept as large of ducting as possible throughout. We have had zero issues with cooling with the exception of a little heat buildup in the top 1000 sq ft. It has a large southern exposure, lots of south windows, and I have not installed the window trim and any blinds so it's a great greenhouse effect. I knew that we were going to be a little light on the airflow up there, but it's a rarely used area of the house. It will be 3-4 deg hotter upstairs in late afternoon day. If I cared to, I could adjust registers downstairs to force more up and make that a bit better, but it's not been a real issue. Existing air handler is an ECM unit however it's an earlier unit and the control board is not very configurable/nor smart. I can fix that easy, but I have another better/newer air handler I'll be swapping in shortly.

There is a continuous non-powered roof vent all along the ridge line, and additionally there is a powered vent as well. I say powered, but it's not connected. Also, the roof has a radiant barrier stapled 3.5" from sheathing. Southern wall also has this radiant barrier as well.

From what I've been reading here and my low temp sources, I've been wondering about 4" spacing for my radiant floor. All floors, with the exception of laundry room and two bathrooms, are 3/4" oak. Subfloor is 3/4" pine laid at diagonal and 3/4" ply. 2.25" of low conduction wood isn't great of course, but there isn't a single bit of carpet anywhere at least. At this point, staple up is my only viable option.

Does anyone have any real world experience with 4" spacing? AC, I know you said that one of the software packages you were playing with wouldn't simulate down to 4". Is that correct? Worst case I suppose would be to try it and then boost the output water temp put out by the heat pump via the wood boiler if necessary, or just take the COP hit with higher output water temp. It's still way better than strip heat.

Len

[randen]

Superlen

I have first hand experience with staple up. I had a oil fired boiler that supplied 160-180 Deg. F water to the zone. IT PROVIDED NO HEAT!! As we had latter changed to Geo-thermal heat pump as you may expect even less than NO HEAT.

DON'T WAIST your time and money with staple-up!!!

I would suggest to install a system like the Uponor hydronic floor which is applied to the top of the floor. Yes you will have to remove the already installed wood floor BUT. the money you will save with a Geo-thermal system will easily replace the cost of the floor.

The comfort is UN-PARRALLELED The heated floor is nirvana!!


Randen

[AC_Hacker]

Originally Posted by superlen

Does anyone have any real world experience with 4" spacing?

Daox has experience installing a very close-space floor. Hopefully he will chime in here. His floors were close-spaced, but not 4".

Originally Posted by superlen

AC, I know you said that one of the software packages you were playing with wouldn't simulate down to 4". Is that correct?

As I recall, it might have come close to 4", but I wanted to see what even closer spacings would be like. It would be worth your time checking it out. It is very easy to do what-if analysis. You'll end up with an intuitive understanding of how changes in your design will affect the overall performance.

I would highly recommend that you heed randen's advice regarding top of floor radiant. Granted, his location (near Toronto) means that his Heating Degree Days are much higher than yours, but the efficiency of above floor install is far superior, no matter what your latitude.

You could do a top of floor PEX/plate install like Vlad, it worked great for him.

Or you could do PEX in 1.5" Gypcrete. We have gypcrete installers on board who can advise you of the details.

Sincerely,

-AC

[superlen]

I'll table the radiant discussion for now as it's only a piece of the puzzle.

While I do want to use the spring water for something, logic would say to run new supply/return lines and use the existing loop field. In that scenario, what connection method would everyone recommend for the 3/4" pex lines I have in the ground already?

I seem to recall that you can't fuse pex so I would be left with a mechanical connection that most likely will cause some issue sometime in the future. I thought about bringing the 3/4" up nearer the surface (18-20") at the connection point to the supply/return and making that connection in a box so that I could easily inspect/repair if necessary. 95% of the loops would still be at 6' of course. This would require 5 boxes and a small portion of the supply/return lines to be at 20" depth. I would then drop back to 6' deep on the 200' way out and back to the loop field from the house to pick up whatever additional heat transfer I could gain in transit. That amount of heat exchange might be small due to laminar flow in the larger pipe.

Thoughts?

Len