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Old 11-07-12, 05:18 PM   #31
jeff5may
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Default Yaay, success! Wait, nope.

I got the unit working last weekend! I'll post pics as soon as I go back inside the case. It ran sweetly until sometime today. When I came home from work, i noticed no puddle below the unit, no frost on outside coil. I went inside and observed no heat, unit purring away...?? Upon further inspection, I found that the high side service valve / tube I brazed in had rattled itself in two.
Oh well, I need to get back in there anyway to hide stuff and tweak anyway.

Note: the unit is in prototype phase; it's gonna look bad until I trust it. The wife says it has to be done before Thanksgiving since everyone will be coming to our house this year.

A quickie view of the failure. I bent the two service tubes a little so they would fit through the vent window for easy access... To get to the liquid line, I have to open the case.

From what I observed over the 4 days I had this unit running, I know it will provide more than I expected.Temps here have been well into frost territory at night. The unit puts out too much heat to run it all out; Saturday night I had to let it cycle when the house got to 85! Outdoor temp at that time was 37.
I've got some concerns, though. Mainly, I don't trust that the txv is not overfeeding the evap coil when it's cold outside. Sunday night / Monday morn it got down to 26 deg f and the suction line was frosted heavily all the way to the compressor body. When I adjusted the charge, it was around 60 deg f outside. It had 6 degrees superheat in heating (txv) and 10 degrees superheat in cooling (cap tube). When the unit defrosted, it melted from the outdoor coil to the reversing valve, but from the rev valve to the cxr the line stayed frozen. Strange. But then again, the unit finished defrosting in like 3 minutes.

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Old 11-15-12, 04:42 AM   #32
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Ok, back in business. I adjusted the superheat up one full turn on the valve to eliminate doubt about slugging the compressor. It was a good thing. Now I have a larger temp spread and more heat when it gets cold.I'm starting to trust this thing.

check valve, cap tube,liquid line service port

condenser side of things... txv, filter drier,and strainer loop came out of a scrapped lennox. White wire is defrost thermistor.

reversing valve and sensing bulb for txv. I had to insulate some lines to keep the txv from hunting. before it's finished, most all vapor lines will be insulated.

Last edited by jeff5may; 11-18-12 at 05:08 PM..
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Old 11-15-12, 10:48 AM   #33
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Ok, back in business. I adjusted the superheat up one full turn on the valve to eliminate doubt about slugging the compressor... I had to insulate some lines to keep the txv from hunting. before it's finished, most all vapor lines will be insulated.
Great going.

Heat for Thanksgiving will certainly be appreciated!

Yeah, turning a scrap air conditioner into an efficient heating machine is truly a win for the DIY team.

From the beginning of my obsession with hacking these cast-off assemblies, I have been struck by the fact that for little money, these conversions can efficiently assume the load of heating parts of, or even all of a house or shop, or heating water for domestic use (as Hv23t is doing) or using the water for all or part of home heat.

I think that too much, we have become accustomed to thinking that 'central air' is the only way to heat a home and that we have to hire experts to do it for us.

Well, you are proving that there is another way... keep it up.

Randen, a machinist up in Canada, built a real beauty out of an old 3 Ton AC. He put in an extensive ground loop system to enable his unit to extract heat from the earth, and he is successfully heating his machine shop with his setup. Last winter, he sent me an email, from Argentina thanking me for making available the information to tackle an AC-to-GSHP conversion. He has, several times remarked how much money he has saved with his system, compared to using oil heat. In fact, I'd guess that the money he saved from his homemade GSHP system, went a long way toward paying for his trip to South America.

So, I think we're really on to something here. And everyone who has tried to build one of these systems, and posted their results... their successes and their mistakes, is contributing to the 'lore' that others might learn from.

Your project is providing heat in time for Thanksgiving... that's a very good thing. But because you have gone to the trouble of posting your results, you are warming up much more than one room...

Best,

-AC
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Old 11-18-12, 08:21 PM   #34
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AC,

I think I'm beginning to get the bug you speak of... I'm getting ideas on how to improve upon this creation already. As it is, I can live with it until after Thanksgiving. It puts out lots of heat until outdoor temps hit about 35 degrees F. It then starts dropping in output down to about 25, where the coil outside just isn't big enough to absorb the load. Heat production peters out at about 20. I don't have concrete numbers to throw around, but I learned a lot about TXV metered setups with this one. While tweaking / observing this unit, I could see what the valve was doing on the gauge and feel the resulting temperature swing indoors. Man, these things fight for you while you're not there. I can see why the establishment charges so much for them: they're worth it.

You amateur experts seem to be finding the same thing: whether air or water source, the outdoor loop of the system has to be made larger than you think. A bigger loop translates to better performance and costs more. Too small is cheaper, but when you need it the most, your loop has nothing to give. No amount of conjuring or conniving will help move more heat.

So for this unit, I'm satisfied with it down to about 25 degrees F. In Kentucky, the average winter lows are in the 20's or 30's. The only time the temp stays below 25 for long is during a cold snap. Temps will drop into single digits at night. After three or less days, temps are back into the 30's and up. So this unit will work well probably 350 days of the year, at least during the daytime. On the coldest 15, it can freeze with the rest of us.
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Old 11-19-12, 12:16 AM   #35
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So this unit will work well probably 350 days of the year, at least during the daytime. On the coldest 15, it can freeze with the rest of us.
Hey, that's wonderful for you!
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Old 11-19-12, 12:31 AM   #36
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AC...I think I'm beginning to get the bug you speak of... I'm getting ideas on how to improve upon this creation already.
Yep, you got the bug alright. And as far as I can tell, it's incurable.

So, I sure do agree that bigger heat gathering area is better, but there is a sweet spot, after which incremental increases only give marginal improvements.

The commodity air conditioner (that's pretty much every one you have ever seen) is designed primarily for the profit of the company that makes them. They want the customers to be satisfied enough that they would be willing to buy another unit. You can improve on the design, but more knowledge and experimenting is ahead.

I probably said it before, but if you can use earth or water as your source for the heat pump to extract from, you'll see sizable improvements.

So, if you live near a lake, you have it made. If a creek is running next to your house, that cold water contains a lot of heat. If the earth where you live is drillable or trenchable, you have a wonderful source there.

The principle is that your evaporator coil is either direct with a liquid, or through a water/HX arrangement, is in indirect contact with the earth, down where the temperatures are warm while the cold winter winds are howling past your door.

Otherwise, as you are finding out, through most of the winter, an ASHP will work just fine, but somewhat less efficiently.

So, I don't know if there are any sizable towns near where you live, but you might check out mini-split heat pumps, just to see how they're built. I actually bought a small one to tide me over while I worked on my ground source unit. The small unit works very, very well. But I have noticed that the HX where the fan draws in air is really quite large, especially compared to a typical A/C unit. I would guess that that HX is easily 2x to 3x the size of an A/C evaporator. The mini-split uses rather thin HXs with either single rows of coils or double rows of coils at the most, but the height and width are quite large. The fan is quite large too, compared to an A/C.

There were mini-split A/Cs before there were mini-split heat pumps, so you might look into something like that. Acuario did a great write-up on converting those kind of units. He used them to heat his swimming pool, and later applied the same kind of hacked units to heat his house.

If you can lay your hands on a working R-22 mini-split A/C, grab it fast, for it will be prime hacking material.

The ones with 'inverter technology' are better, more efficient units, but the inverter bit and the complex electronics can be paralyzingly complex.

However, if you already have a multi-trace oscilloscope and a signal analyzer in your home and you already know how to use them, please ignore the previous paragraph.

If I can be of further help, please let me know.

Best,

-AC
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Old 11-25-12, 11:12 AM   #37
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Default Murphy's law strikes again...

The unit has been running faithfully since the last repair until sometime this morning. I moved the defrost thermistor to the other side of the evaporator circuit, near the TXV, to ensure the coil was defrosting completely. In its original location, the control was terminating defrost soon after hot gas began to flow into the coil. Ice was building up on the bottom inch of the coil, since the melted frost didn't have time to drain. Now, the evap coil is bone dry and the unit is growing icicles on it at the drain point! At least it was...

Last night when I checked, it was 23 degrees F outside, and the unit was blowing 90 degree air (72 degrees indoors at the furnace). This morning, I woke to find the unit blowing 68 degree air and 10 psi suction pressure. I unplugged the beast and let everything equalize. Pressures leveled out at 50 psi. Great. I popped the cover and started spraying everything with soapy water. This time, I found a leak at the joint where the discharge line leaves the compressor. Oh well, at least it's not a joint I brazed. Hopefully this will be the last bug.
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Old 11-25-12, 12:20 PM   #38
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Hope the leak is at a good spot.. Accessible to the torch and easy to heat-sink etc.

I'm keeping my fingers crossed, praying the Sanyos keep up their output. (& keep their R410A)
So far, they seem to be working okay. But the winter has just started.

Seem to be using about 0.8 kWh per hour (average) these days.
Not too cold yet, but getting there.

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Old 11-25-12, 06:41 PM   #39
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I unplugged the beast and let everything equalize. Pressures leveled out at 50 psi. Great. I popped the cover and started spraying everything with soapy water. This time, I found a leak at the joint where the discharge line leaves the compressor. Oh well, at least it's not a joint I brazed. Hopefully this will be the last bug.
Awesome trouble-shooting, just awesome!

There should be some kind of black belt for this...

Best,

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Old 12-02-12, 09:27 PM   #40
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Update:

Right around Thanksgiving, the unit developed a leak at the top of the compressor. The stock tubing the manufacturer used was rather thin and seems to have vibrated itself apart. You can see the spot that popped in the previous post I made, taking a picture of an access valve I brazed in that had vibrated itself apart in the same way. The tubing below the slip coupling I brazed in failed. What I did this time was made a longer slip coupling that now fits all the way down to the cxr. I left a 1/2 inch piece of the factory tubing for a stub to line up piping, and blobbed on a generous amount of silfos at the cxr shell to increase contact area at that joint. I then lined everything up and slipped my new fitting down into this puddle of silfos. Now there is a flange-type joint at the top of the compressor, so hopefully it will have added strength and rigidity. Down at the reversing valve, I installed some foam between it and the cxr shell and wired them together to reduce any excessive vibrations from occurring in the discharge line that has caused two vibration-related leaks. Re-purge, vacuum, recharge. Unit has been running good since 25 Nov.

The weather got mild again this week, so the unit has not been running anywhere near constantly. Last week, it pretty much kept the gas furnace from running any long cycles. Normally, the gas furnace runs every fifteen minutes when temps go below 45, and more often the colder it gets.

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