The Homemade Heat Pump Manifesto

[randen]

Vlad

Valid questions. I myself am definetly not a AC guru by any stretch of the imagination. I only have a basic understanding of the system. My GSHP's 4 way valve switches the heat exchangers source from ground loop to infloor/airhandler for the seasonal heating /air conditioning demand. The working temps don't vari greatly. The temps stay well within the envelope of liquid and superheated gas for the pressures charged. For example when I change the ground loop input/output (8 Deg.C) to air-conditioning the evaporator will operate in the same range of temp (2-10 Deg.C) and the HX condensor that is changed from the infloor/ airhander loop to the ground loop will settle into sending heat out at about 28 deg.C. and return of 14 deg C. Therefore the the temp/pressures remain within a workable limit in either direction.

To gain the most heat for unit electrical power I adjusted the charge according to the compressor current draw and condensor heat output (Temp) I placed a ampmeter on the power line and watched the temp on the condensor out-put and slowly added or removed refrigerant to get the best output. I'm using propane (R290) for the refrigerant and the pressures are about half of the R22 pressures. The compressor should last for a long time. It may not be totally scientific but its working well.


Randen

[Vlad]

randen, As you mentioned, your system is cap.tub.
Cap. tub. systems are critically charged systems. The amount of charge is not easy to determine. You can not only use COP factors, because you have things in yous system like compressor. You MUST HAVE superheat @ about 20F, otherwise your compressor is getting liquid refrigerant in suction line. Liquid in suction line will kill compressor, you have no choice. It is like if I feed you with a small amount of poison every day, your liver will give up. On other hand you want only just enough superheat because it lowers COP.

[Vlad]

Because my heating is the only radiant floor heat I have some challenges with fresh air and exhaust air. I was thinking of installing HRV but I will still need AC during summer and add more heat after HRV in heating season. The price of HRV is steep and savings will (if at all) show in few years from now.

I got for free two small WSHP from office building. One is about 9000 btu the other is about 12000 btu. They both 265 volt R-22. Compressors condition unknown (I am getting 220 and 120 instead from eBay). The smaller is TXV (has 20 oz charge) the bigger is Cap Tube (has 11 oz charge). This fact shows how Cap Tube systems are charged more accurate.

Because I have my CFC card I can buy r-22 and use it, but it is too easy for DIY. I can just change compressors and charge them by label (adjust amount for r-290) but it is again too easy.

I think we should look at heating as HVAC, because it is integrated part of our house. For myself I decided to have heat as radiant floor heat (the best). AC for summer must be a part of ventilation system (cool air distribution). Fresh air supply as part of ventilation as well.

My smaller WSHP will be used as heat supplement for heating fresh air during heating season (9000 btu will be enough to heat up fresh cold outside air). In the summer it will work as AC to add capacity to bigger unit. The bigger WSHP unit will work as AC with reversing option.

At one point I was thinking of utilizing warm exhaust air and using it as heat source. After reading AC's posts I see the biggest challenge in GSHP. It is outdoor loop. If we can extract btus from somewhere it means we need less from ground loop. I was thinking to add air coil in series with water cooled evaporator. The exhaust air (we blow it outside anyways) will pass through air coil and give back its heat to air coil. The problem is put air coil before water coil or after. If we put coil before it will freeze up (warm moist inside air is perfect for this) If we put after water coil COP will be lower.

I think we can discuss some of this topics. We are as DIYers are not afraid to chop out system into pieces and braze it back couple more times

[Vlad]

One day I was looking for r-22, like always source #1 is eBay. I found r-22a in results. I started looking for more info. I found big discussion on "hvac-talk". Nobody tried it but everybody "heard" from "body" scary story.... Everybody had his OPINION but nobody eve tried it, what a bunch of ....("professionals"). Finally I gathered some info, that made me think to try it.

I am still in process (nothing is done, waiting for parts). R-22a is a mix not just pure propane. I think it is great because everybody can legally play with AC using it (initially system must be properly evacuated). Even considering that most of laws that regulate refrigerants is pure BS we still have to follow them.

When one refrigerant is replaced with the other one many things must be redesigned in the system that was originally designed for original refrigerant.
One of this things must be metering device (MD). If it was cap tube, then it was designed for r22 r22a(propane as well) has completely different properties. Now cap tube will not work properly. The problem with cap tube is it is fixed it will not readjust itself. For this reason I will go only with TXV. TXV is more forgiving. It is like driving auto VS manual (auto will never forget to shift )

The other problem with cap tube is DIY. Yes we don't have enough resources to run thousands of tests when we "design" our system. If you make mistake with heat load and over-under size condenser or evaporator cap tube will never let your system run properly.

R22 and r22a PT charts look really close, it means that TXV with r22 charge in its bulb might work OK and it will provide proper superheat.

[AC_Hacker]

Originally Posted by Vlad

...We are as DIYers are not afraid to chop out system into pieces and braze it back couple more times...

Music to my ears!

-AC_Hacker

[Pegasus]

Hello all, and many thanks for the manifesto (Read it all).
From what i can tell we share the same thinking regarding ecology, economy and DIY.

I have a well insulated home at Chania - Crete, Greece. My Heating system consists of :
- 4 evacuated tube sollar collectors from a local factory (0 emitions)
- A wood stove with a boiler (Carbon Neutral, localy obtained Olive tree trimmings)

The heat sources above "charge" a 800 lt Water Heat storage + DHW (Tank in Tank) that in turn "feeds" the demand : Floor (concrete) + Wall - Ceiling (Gypsum "Plaster" board) Hydronic Heating (at a temp of 30-40 Deg C).

I also have a 150 m2 Geothermal Heat exchanger at a 2m depth (placed below the building foundation) with no option for expanding because of the hard rocky plot i own
(used for cooling WITHOUT any heat pump till now).

For the last five years i have no problem in meeting the heating demands of the house, but the cooling is an other matter.

The initial planning was to use the solar collectors both for heating and cooling after the incorporation of an evaporation circle heat pump aided by the ground loop. I found some interesting implementations of that concept, but are either way too expensive (no more money!!!) or yet under development.

After 5 years of waiting i decided to modify a small A/C (~1kw) to a DIY Geo heat pump, in order to help both in heating (charging the heat storage) and in cooling (directly) the house. Its my first time i deal with HVAC and i only have a general understanding of it.

Your Thread has been a revelation and just in time i must say. I have already ordered the HX (though E-bay) and i know a HVAC technician willing to help me with the modification (sceptic though), mostly providing the tools I'm gona need and a few advice.
Questions:
- Any newer progress - photos of your project (how is the hand going)?
- What about using old fashion mechanical pressure valves for LS and HS in staid of fancy electronics?
- A gas leek detector- alarm wouldn't be a nice ad-on for the R290 i plan to use ?
- What would be the 4 way valve and the pressure - temp. control logic for the system (the control logic in general) ?

Any response, from any one, would be of assistance, thanks a lot again.

[AC_Hacker]

Originally Posted by Pegasus

I have a well insulated home at Chania - Crete, Greece.

Peagsus,

Welcome to the conversation! And how excellent to have a fellow EcoRenovator in Greece. It is very cold and rainy where I live, so it is good to hear from you, it makes me feel a little warmer already!

Originally Posted by Pegasus

My Heating system consists of :
- 4 evacuated tube sollar collectors from a local factory (0 emitions)
- A wood stove with a boiler (Carbon Neutral, localy obtained Olive tree trimmings)

The heat sources above "charge" a 800 lt Water Heat storage + DHW (Tank in Tank) that in turn "feeds" the demand : Floor (concrete) + Wall - Ceiling (Gypsum "Plaster" board) Hydronic Heating (at a temp of 30-40 Deg C).

I also have a 150 m2 Geothermal Heat exchanger at a 2m depth (placed below the building foundation) with no option for expanding because of the hard rocky plot i own
(used for cooling WITHOUT any heat pump till now).

For the last five years i have no problem in meeting the heating demands of the house, but the cooling is an other matter.

Sounds like you have been very resourceful and clever in your work so far. If only people in North America were as thoughtful as you are, the world would be a more peaceful place.

Originally Posted by Pegasus

After 5 years of waiting i decided to modify a small A/C (~1kw) to a DIY Geo heat pump, in order to help both in heating (charging the heat storage) and in cooling (directly) the house. Its my first time i deal with HVAC and i only have a general understanding of it.

Your Thread has been a revelation and just in time i must say. I have already ordered the HX (though E-bay) and i know a HVAC technician willing to help me with the modification (sceptic though), mostly providing the tools I'm gona need and a few advice.

This is going to be very interesting. Please take photos and share them with us... we all want to see how your project goes.

Originally Posted by Pegasus

- Any newer progress - photos of your project (how is the hand going)?

As you know from reading the 'manifesto', I ran my compressor for a couple of months last winter and was able to enjoy useful heat for my basement, at a reasonable cost.

I also learned that my ground loop was so long that it was necessary to use a large pump to pump water at the rate I needed for my heat pump. So last fall , I dug to the central point in the ground loop and I now will be able to run two loops in parallel.

Here is what the loop field looked like before:

Here is locating and uncovering the midpoint:

And here we are welding in the new pipes and routing the pipes into the basement:

Here is the loopfield which is now two shorter loops instead of one overly-long loop:

Now, I will only need a pump 1/4 the size that I needed before. I will not get any more heat from my loop, but I will not lose so much energy to the pump.

Originally Posted by Pegasus

- What about using old fashion mechanical pressure valves for LS and HS in staid of fancy electronics?

You must be talking about the metering device that regulates the flow of refrigerant into the evaporator. Most small air conditioners use a very small tube called a cap tube for this. The one that is already in your air conditioner will work for your project. If you use propane, it will not be exactly the right size, but it will still work very well.

There is another kind of valve called a Thermostatic Expansion Valve (AKA: TXV) that will work somewhat better for your project. I would reccommend using the cap tube for your first project. Later if you want to try to improve your homemade heat pump, you can replace the cap tube with a TXV of the proper size.

The Electronic Expansion Valves are really an advanced topic and might require a lot more technical understanding that you may have at this time.

I think you will be very pleased with a cap tube.

Originally Posted by Pegasus

- A gas leek detector- alarm wouldn't be a nice ad-on for the R290 i plan to use ?

There is potential hazard to using propane. But if your heat pump is outside, if it leaks, there will be no problem.

Refrigerant leaks are usually very, very slow, and the propane will mix with air and ex-filtrate out of the house and never get to a dangerous point.

However, if your heat pump is in a basement, it could be a problem because propane is heavier than air, and can build up to dangerous levels.

Also, if your house is very, very tight, propane could build up to dangerous levels.

If your heat pump had a large compressor, like a over a ton, there could be enough propane even with a slow leak to be a dangerous problem.

If you feel you need a leak detector, I would not discourage you from getting one.

Originally Posted by Pegasus

- What would be the 4 way valve...

I'll let randen take that one...

Originally Posted by Pegasus

...and the pressure - temp. control logic for the system (the control logic in general) ?

This is an area where we are not represented very well at this time. If any readers want to offer advice here, it would be greatly appreciated.

I have looked at a board that Xringer found and it looks like it will work very well for my purposes.

Here's where I got mine...

At this time, I have only used it for monitoring temperatures throughout my house, but my impression is that it will only require a few hours to make it work for me.

Xringer is embarking on a project to make a small heat pump water heater, so he will most likely do development on the CAI board that is very similar to your project.

Originally Posted by Pegasus

Any response, from any one, would be of assistance, thanks a lot again.

I suspect you will have plenty of assistance.

-AC_Hacker

[Geo NR Gee]

Originally Posted by Vlad

When one refrigerant is replaced with the other one many things must be redesigned in the system that was originally designed for original refrigerant.
One of this things must be metering device (MD). If it was cap tube, then it was designed for r22 r22a(propane as well) has completely different properties. Now cap tube will not work properly. The problem with cap tube is it is fixed it will not readjust itself. For this reason I will go only with TXV. TXV is more forgiving. It is like driving auto VS manual (auto will never forget to shift )

The other problem with cap tube is DIY. Yes we don't have enough resources to run thousands of tests when we "design" our system. If you make mistake with heat load and over-under size condenser or evaporator cap tube will never let your system run properly.

R22 and r22a PT charts look really close, it means that TXV with r22 charge in its bulb might work OK and it will provide proper superheat.

Not sure what you are saying here? Are you saying the cap tube for R22 and R22a is the same, or Not the same?

[Vlad]

Geo NR Gee,
R-22 and R-22a have close pressure-temperature characteristics. Their PT charts look very close. But they have many other properties which are different. If you look at refrigeration equipment, then you can say that compressor is a heart of the system, but metering device MD is a brain.

Cap tube is even hard to replace with identical one. You can't just go with size bigger or smaller, longer or shorter. The SYSTEM will not work as it supposed to work. You are trying to adopt it for different refrigerant.

Check this video:

Heat Pump Water Heater - YouTube

and tell me what is wrong with it. It works, but there are some mistakes that will make system to fail.

The short answer to your question will be cap tube for R-22 and for R-22a must be different.

[Vlad]

This is easy basic manual. It shows where components must be located.

http://www.danfoss.com/NR/rdonlyres/.../0/filter5.pdf