Hacking a 12K BTU water source heat pump

stevehull · 07-12-15, 05:07 PM

Recently I posted on a problem I am having in my guest house. It is tight as a drum, well insulated, but getting moisture out is a problem. When not occupied by guests/friends (most of the time) , I set the thermostat to about 83F (in summer). Running a 600 watt dehumidifier does remove moisture, but it adds heat. Against my Yankee heritage . . . .

The existing two ton geothermal heat pump in the unit barely runs enough to remove water vapor at that air temp set point. I am in Oklahoma and the average daytime high temp here is about 95 or so. At night, (relative humidity of 100%) it dips to 75 F, but the air is also at the same dew-point. I bet that is where the moisture comes from.

What to do . . . . My wife and kids were gone to cousins this week, so I had the place to myself. Time on my hands . . .

This past Friday, I went to my friends at the local AC shop (are dealers for both WaterFurnace and Climate Master) and told them my problem. At low cost, I have done a lot of consulting for them over the years and they told me to go search the "junk trailer".

So, I scavenged though their trailer and got run out by wasps. Two cans later of "knock down spray" and I got lots of old and disused junk. My "find" was an old two ton R22 unit (circa 1988) with a bad compressor, blown out electronics, a bad blower motor, etc. Got this for scrap price ($2). The cabinet was most value!

Then, they found an old, old 120 VAC reciprocating compressor "about the right size" and gave that to me for $10. No literature, but looks unused. Found out later, it is a lot smaller than the old one in the unit, but the price was right. It came with capillary tubes, and Schrader like valves, but looks like it was made in the '70's. The shop boys are calling my vision - Hull's Frankenstein. The damn wasp spray was almost more than the cost of parts.

Borrowed a tank of dry nitrogen and they said compressor should have oil in it (it does slosh a bit when inverted).

Friday, I troubleshooted and have replaced the burned out relay (fried contacts), fixed up the motor blower bearings, soldered in a new wire to the 1/12 HP AC blower motor, replaced the shorted starting capacitor, rewired the electrics and have sweated in the "new" compressor. Also found out the low voltage AC transformer was shot (primary to secondary short), but found one of those in the parts bin here.

I have wired it up so the reversing valve can work (it does mechanically "sound like" it works) and will use the capillary tubing from the new compressor.

The evaporator condensate pan was rusted and had a few holes. The "new" condensate pan is now a used (but cleaned of paint) plastic roller pan with a hole drilled in it and a silicon sealed tube. One attraction is that these paint pans are tilted so there is now better drainage towards the drain tube.

So far, the blower spins (no bearing squeal), the transformer energizes the relay and I have 120 VAC into it. Gonna get free R22 as they thought the BBQ gas was a joke (it wasn't and it isn't!). But it is all the right price. Yes it is kludged up, but this will give me a small unit that you simply can't buy.

This AM, tested the water lines and they hold pressure with no leaks. Put a gate valve on the water inlet side and adjusted valve for a water flow of about 2 GPM. Re insulated all the evaporator lines with wrap on foam tape. All old insulation was just "crunchy" and turned to black dust when you removed it.

My calculations indicate a current draw of about 9-10 amps. Very hard to read the old paper label on the compressor. Given the size of the compressor and evaporator coil, I expect about a 30 F delta t across it and some 200-400 CFM from the blower, I hope to get about 14,000 BTU (1+ ton) out of it. Not a great EER if my current calculations are correct . . . .

Have done a LOT of soldering and welding before, but never brazing. This copper brazing was really quite easy. Started on some scrap copper. Used dry nitrogen as a flow through purge to prevent interior scaling. As AC has suggested, "cherry red" is the color you want, then the rod just flows . . . .

Purged, then filled compressor and lines with nitrogen; hope pressure will be there tomorrow. So far, at four hours and no drop in pressure.

Tomorrow, the boys are coming out in the AM with a tank of R22, a super vacuum pump and drier. I hope and pray that this works or I will be the butt of many of their jokes!

But it has been fun!

Steve

07-12-15, 05:07 PM	#1
stevehull Steve Hull Join Date: Dec 2012 Location: hilly, tree covered Arcadia, OK USA Posts: 826 Thanks: 241 Thanked 165 Times in 123 Posts	Hacking a 12K BTU water source heat pump Recently I posted on a problem I am having in my guest house. It is tight as a drum, well insulated, but getting moisture out is a problem. When not occupied by guests/friends (most of the time) , I set the thermostat to about 83F (in summer). Running a 600 watt dehumidifier does remove moisture, but it adds heat. Against my Yankee heritage . . . . The existing two ton geothermal heat pump in the unit barely runs enough to remove water vapor at that air temp set point. I am in Oklahoma and the average daytime high temp here is about 95 or so. At night, (relative humidity of 100%) it dips to 75 F, but the air is also at the same dew-point. I bet that is where the moisture comes from. What to do . . . . My wife and kids were gone to cousins this week, so I had the place to myself. Time on my hands . . . This past Friday, I went to my friends at the local AC shop (are dealers for both WaterFurnace and Climate Master) and told them my problem. At low cost, I have done a lot of consulting for them over the years and they told me to go search the "junk trailer". So, I scavenged though their trailer and got run out by wasps. Two cans later of "knock down spray" and I got lots of old and disused junk. My "find" was an old two ton R22 unit (circa 1988) with a bad compressor, blown out electronics, a bad blower motor, etc. Got this for scrap price ($2). The cabinet was most value! Then, they found an old, old 120 VAC reciprocating compressor "about the right size" and gave that to me for $10. No literature, but looks unused. Found out later, it is a lot smaller than the old one in the unit, but the price was right. It came with capillary tubes, and Schrader like valves, but looks like it was made in the '70's. The shop boys are calling my vision - Hull's Frankenstein. The damn wasp spray was almost more than the cost of parts. Borrowed a tank of dry nitrogen and they said compressor should have oil in it (it does slosh a bit when inverted). Friday, I troubleshooted and have replaced the burned out relay (fried contacts), fixed up the motor blower bearings, soldered in a new wire to the 1/12 HP AC blower motor, replaced the shorted starting capacitor, rewired the electrics and have sweated in the "new" compressor. Also found out the low voltage AC transformer was shot (primary to secondary short), but found one of those in the parts bin here. I have wired it up so the reversing valve can work (it does mechanically "sound like" it works) and will use the capillary tubing from the new compressor. The evaporator condensate pan was rusted and had a few holes. The "new" condensate pan is now a used (but cleaned of paint) plastic roller pan with a hole drilled in it and a silicon sealed tube. One attraction is that these paint pans are tilted so there is now better drainage towards the drain tube. So far, the blower spins (no bearing squeal), the transformer energizes the relay and I have 120 VAC into it. Gonna get free R22 as they thought the BBQ gas was a joke (it wasn't and it isn't!). But it is all the right price. Yes it is kludged up, but this will give me a small unit that you simply can't buy. This AM, tested the water lines and they hold pressure with no leaks. Put a gate valve on the water inlet side and adjusted valve for a water flow of about 2 GPM. Re insulated all the evaporator lines with wrap on foam tape. All old insulation was just "crunchy" and turned to black dust when you removed it. My calculations indicate a current draw of about 9-10 amps. Very hard to read the old paper label on the compressor. Given the size of the compressor and evaporator coil, I expect about a 30 F delta t across it and some 200-400 CFM from the blower, I hope to get about 14,000 BTU (1+ ton) out of it. Not a great EER if my current calculations are correct . . . . Have done a LOT of soldering and welding before, but never brazing. This copper brazing was really quite easy. Started on some scrap copper. Used dry nitrogen as a flow through purge to prevent interior scaling. As AC has suggested, "cherry red" is the color you want, then the rod just flows . . . . Purged, then filled compressor and lines with nitrogen; hope pressure will be there tomorrow. So far, at four hours and no drop in pressure. Tomorrow, the boys are coming out in the AM with a tank of R22, a super vacuum pump and drier. I hope and pray that this works or I will be the butt of many of their jokes! But it has been fun! Steve __________________ consulting on geothermal heating/cooling & rational energy use since 1990 Last edited by stevehull; 07-12-15 at 08:34 PM..