The Homemade Heat Pump Manifesto

[Geo NR Gee]

Originally Posted by AC_Hacker

It would be much easier to diagnose if you could tell me HS & LS pressures, after the unit has been running about ten minutes.

Did you set it up so that you could read HS and LS pressure? I guess you installed at least one Schrader valve on the LS for charging with propane

Tell me HS & LS pressures after 10 minute running.

-AC_Hacker

AC,
I put in the HS port and took out a bit of refrigerant. I ran it 10 minutes watched the gauges and the HS began to creep over 225, so I removed more and got it to about 175, but the LS never goes higher than about 25 now. The compressor is only drawing 1.1 amps!!!!!!!!. WOW

With R22 it was drawing 6 amps.

The wiring going to the fan area is drawing 4.3 amps. With the old R22 it was pulling 4.7amps.

The temperature coming out of the compressor now is 170 f. and the LS is 70 f.
To recap.......
----------------------------
R22
HS with R22, 100
LS with R22, 40

amps 6 at compressor
amps 4.7 at control board area
-----------------------------
R290

HS with R290, 170
LS with R290, 70

amps 1 at compressor
amps 4.3 at control board area
-----------------------------



Should I take more refrigerant out?
The design pressure on the label is 200 Low and 400 High

Thank you,
Geo

[AC_Hacker]

Originally Posted by Geo NR Gee

R290

HS with R290, 170
LS with R290, 70

amps 1 at compressor
amps 4.3 at control board area
-----------------------------

Should I take more refrigerant out?
The design pressure on the label is 200 Low and 400 High

Thank you,
Geo

Well this photo does tell a story:

From the looks of things, It does look like the miracle of refrigeration is taking place!

> Should I take more refrigerant out?
> The design pressure on the label is 200 Low and 400 High

Those specs are for R-22, if you don't have R-22 they don't really apply anymore.

I'd say you have too much, Randen's technique of watching the amperage and measuring the heat rise in the water would be great if you were running your condenser as a water HX, which you aren't.

Perhaps you could measure the temp of your condenser (the hot HX) and see if there is a charge level that will give you a high condenser temp and a low amperage draw.

Any way you cut it, you are almost there.

We need more photos...

-AC_Hacker

[MN Renovator]

"I think a 4' x 8' box with a couple of levels of metal lath painted black, would make an excellent pre-warmer. Top it wil glass or plastic, forget insulating the box, be sure to not restrict the flow of air into the ASHP." Good size considering the available size of plywood. Unless I'm missing something, the inside of the box should be painted black too. I don't see the metal lath doing that much since most of the light will pass through the mesh and hit the plywood. The airflow in the box and convection(when the heat pump is off) should get most of that heat off of the black painted plywood. A very hot box should make for a much larger boost to efficiency for a minute or so when the unit first kicks on in the middle of a sunny day.

[AC_Hacker]

Originally Posted by MN Renovator

...I don't see the metal lath doing that much since most of the light will pass through the mesh and hit the plywood.

Well, it might take three layers to do the trick. The idea is to have all the sun's energy heat up the metal lath and to quickly release it into the air stream.

I can't claim ownership of the idea, it came From Sunspots: An Exploration of Solar Energy Through Fact and Fiction by Steve Baer, an excellent book.

-AC_Hacker

[itjstagame]

I have read your entire thread and had an inspiration of my own.

I had been considering purchasing a central a/c condenser and building my own central a/c a couple years ago and I know I can find them fairly cheap used. Now I realize this can be used as heat too.

My thought would be to reverse the flow and set this up as an ASHP with a refriderant-to-water HX on the new condenser side, inside the house. This is probably overkill and maybe I should experiment with an old dehumidifier, if I can find one cheap, but it seems a nice, completely, full-package that is already pretty much designed for this.

My question is, after reading this whole thread and hearing about 4way switches and reversing flow, how exactly does this come in to play? I have been unable to picture it. Obviously the flow through the condenser does not reverse, so I guess what we're really doing, is deciding if the refridgerant should go. So, to change an outside condenser unit to pump heat the way I want, I am guessing I would need to cut the existing connector between the compressor and the condenser, because the output from my compressor will now go in the house, and the 'condenser' will need to feed in to the input of the compressor, so that it becomes an evaporator.

Does that make sense?

Can one buy one of these 4way switches so I have the option for cooling as well?

After that, my goal would be to get a water HX and use the HP to preheat the water in my baseboard heating system. I think it goes hotter than the HP can deliver when the gas lights, so I will still need to work out a control method for when to switch from one to the other.

Do you have any advice or suggestions, or just get some junk and start hacking?

[AC_Hacker]

First off itjstagame, welcome to the conversation!

It looks like a very ambitious undertaking you have in mind, so I advise you to get a cheap, used air conditioner or de-humidifier and start small. You have a lot to learn, if you haven't done this kind of thing before, start small and cheap. The tools you get for your learning projects will be the same tools you will use on your ultimate system.

Originally Posted by itjstagame

...My question is, after reading this whole thread and hearing about 4way switches and reversing flow, how exactly does this come in to play? I have been unable to picture it. Obviously the flow through the condenser does not reverse, so I guess what we're really doing, is deciding if the refridgerant should go.

Here's a picture of a reversing valve:

...and here's adiagram of what's inside of the reversing valve:

...here is a diagram of a heat pump circuit, showing how the reversing valve works in cooling mode:

here is a diagram of a heat pump circuit, showing how the reversing valve works in heating mode:

Originally Posted by itjstagame

So, to change an outside condenser unit to pump heat the way I want, I am guessing I would need to cut the existing connector between the compressor and the condenser, because the output from my compressor will now go in the house, and the 'condenser' will need to feed in to the input of the compressor, so that it becomes an evaporator.

The diagrams should have answered your questions...

Does that make sense?

Originally Posted by itjstagame

Can one buy one of these 4way switches so I have the option for cooling as well?

Yes, you can...

Originally Posted by itjstagame

After that, my goal would be to get a water HX and use the HP to preheat the water in my baseboard heating system. I think it goes hotter than the HP can deliver when the gas lights, so I will still need to work out a control method for when to switch from one to the other.

If you have hydronic baseboards, they are likely designed for higher feed temperatures than a normal heat pump can deliver.

There are some baseboard HXs being built in Europe that will work just fine. You could also put in more baseboards than you would usually need.

Originally Posted by itjstagame

Do you have any advice or suggestions, or just get some junk and start hacking?

I would say get some junk and start hacking, you'll learn a tremendous amount along the way. You will probably answer many of the questions you already have, and the ones you can't answer will be really interesting.

We're here to help.

-AC_Hacker

[Pmorris710]

Geo NR Gee:

I didn't catch what prompted you to jump to propane from R22, but they are similar on a pressure temp chart. If you were dealing with an overcharge you would see temperatures leaving your evaporator near saturation temp according to a temp pressure chart. It looks like a cap tube set up, so really if you are icing the first part of the coil only, that is the point where you run out of liquid refrigerant, which would agree with your 70 degree LS.

My hunch is that you have a restriction. When I see plugged cap tubes, I see a partially warm evap, and a iced up mess in the other part.

If you aren't pulling amps, you aren't producing work.

The tell tale is in the temperatures. If you measure at the exit of the evap, as you add or subtract charge, you should normally see a smooth increase or decrease depending on if you are adding or removing. With a restriction, you will see near ambient temp exiting evap even as you continue to add more. Did you pull vacuum? Long periods of soldering without purge? Many times at the point where liquid line becomes cap tube, there is a screen that will plug easily. Other times the cap tubes them selves are so small that it doesn't take a significant amount of foreign material to block them up. I've changed cap tubes that weren't moving refrigerant, only to find them unblocked once I got them out. If you didn't pull vacuum, and you are pumping air or moisture, you will see spikes in HS without condensing/liquid charge producing.

[Geo NR Gee]

Originally Posted by Pmorris710

I didn't catch what prompted you to jump to propane from R22, but they are similar on a pressure temp chart. If you were dealing with an overcharge you would see temperatures leaving your evaporator near saturation temp according to a temp pressure chart. It looks like a cap tube set up, so really if you are icing the first part of the coil only, that is the point where you run out of liquid refrigerant, which would agree with your 70 degree LS.

Thanks Pmorris710 for your insight. The reason that I changed from R22 to propane (R290) is to experiment on the higher efficiency of propane (R290). According to many studies and tests, it is far superior to R22. Purdue University has a great one on R290 as a substitute for R22.

Originally Posted by Pmorris710

My hunch is that you have a restriction. When I see plugged cap tubes, I see a partially warm evap, and a iced up mess in the other part.

Remember, this is a dehumidier. But I do see that the unit may not have enough charge since it is only iceing up part way up the coil. When I looked at the picture again, I could see at the top what appears to be a sensor. I wonder if that sensor tell the unit that the coil is full of ice and now should melt it to drop into the bucket at the bottom? So thanks to you, I think I don't have enough charge in it.

Originally Posted by Pmorris710

If you aren't pulling amps, you aren't producing work.

Totally makes sense to me now. I just figured that the reason I had lower amps is because of the more efficient R290.

Originally Posted by Pmorris710

The tell tale is in the temperatures. If you measure at the exit of the evap, as you add or subtract charge, you should normally see a smooth increase or decrease depending on if you are adding or removing. With a restriction, you will see near ambient temp exiting evap even as you continue to add more. Did you pull vacuum? Long periods of soldering without purge? Many times at the point where liquid line becomes cap tube, there is a screen that will plug easily. Other times the cap tubes them selves are so small that it doesn't take a significant amount of foreign material to block them up. I've changed cap tubes that weren't moving refrigerant, only to find them unblocked once I got them out. If you didn't pull vacuum, and you are pumping air or moisture, you will see spikes in HS without condensing/liquid charge producing.

Actually, I figured since I was new to brazing and I didn't have time to cut and braze in ports, I would install the quick pierce ones. It was also to eliminate exactly what you stated on having contaminates in the system. I figured once I got this unit working correctly, I would pull the charge, then cut and braze them in. FYI, I did pull a vacuum after I pulled the R22 out of the enclosed system.

Next I will increase the charge to see the ice/frost build up on the coil go to the top where the sensor is. Thank you for the clarification.

[AC_Hacker]

Please note useful new thread which outlines where to get donor units and reasonably-priced HVAC tools.

URL of the thread is listed here.

Regards,

-AC_Hacker

[itjstagame]

Thanks AC_Hacker, that is how I expected it to work.

One thing that bothered me was the expansion valve, or loop of thinner gauge coil. I'm guessing in your last diagram that the pass valves have to be switched at the same time that the reversing valve is?

Yes, I think it makes sense to start small and cheap and hard braze it for heat and worry about reversing in a better model.

I realize that this won't get me as hot a water as a furnace and not as good a cop as GSHP, but should be good learning. I'm not sure with ASHP when it's 20F outside and I'm trying to get heat, but if I can stay above 1 cop (including the energy to run my baseboard circulating pump), I should still be saving money and not using natural gas. I figure I can run the circulating pump much more often at lower heat and cycle in the furnace now and then for cold days or if we get further away from our thermostat set temp.

Obviously the hardest part will be the controller, but I think it could be a very cool system in the end.

One last question, I think there's another thread somewhere but cannot find it immediately. When you charged with R290, did you add oil first before charging? I was thinking of trying the R290 route but was wondering what you do about the lack of oil.
Also did you use a small canister, like a mapp gas canister?

I have pressure gauges from working on cars but need to get a vacuum pump first before I can charge anything.