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jeff5may · 08-20-17, 11:37 PM

Grab somebody's old 10 SEER R-22 unit off of craigs list or letgo or faceb00k marketplace and start a project. I got a goodman 2 ton heat pump unit for 50 bucks this month, and saw a few 1.5 ton units for around the same price. It is peak air conditioning season, and just as window units command a premium price this time of year, people are upgrading their existing central units in droves. They are dumping their old air handlers and outdoor units for pennies on the dollar. That stuff that runs on 240 volts is useless to most.

For most, the hardest part of the project is choosing heat exchangers or building them. If you have an easy way to do geothermal, rig the loop to a plate heat exchanger rated 25 to 50 percent larger than the compressor at standard rates (2.5 GPM per ton, 10degF temperature change). If you are resourceful, you can rig a condenser out of a roll of 1/2 inch tubing inside a bucket or barrel. A moonshine worm, if you will. For 2 tons or less, 100 feet of 1/2 inch tubing will easily fit in a 5 gallon bucket. For the homebrew condenser, give it 3 GPM per ton of capacity. Voila, you're done outdoors. Sell the fan and the outdoor heat exchanger to get your money back out of the unit, or leave it in place (disconnected) to disguise what's crammed inside (small water pump and water to refrigerant HX).

Indoors, run whatever you are comfortable with as a cold air source. Indoor heat exchangers can take many forms, shapes, and sizes. Just remember that the thing will be wringing gallons of water out of the air every day during cooling season. I made one out of a cylindrical air cleaner (copper tubing in place of the hepa filter) and a water heater drain pan that does a good job. It had a 3-speed fan in it, so the fan speed is controlled by the control board i put on it (read below). I sourced a TXV from surplus city liquidators for around $20. You can buy prefab fan coils or air boxes for a hefty price.

The control system is easy to rig also. If you find an outdoor unit that works, you can rig the thing to a standard thermostat of your choice with a few wires and a 24VAC control transformer. Indoors, all that needs controlled is the fan, by way of a relay. I have started using the Qunda brand of control boards in my beasts. Same basic controls as a mini split unit. Cool looking indoor display/button panel that is either LED with blinky lights and 7-segment digits or backlit LCD panel. The non-heat pump controls are cheaper than the heat pump controls. The one I rigged to the air cleaner beast was like $50 off amazon. I had to add a few control transformers to work the reversing valve and compressor in the outdoor unit, because the Qunda board switches everything at line voltage.

Or you can buy a mini split (or window shaker) system and save most of the fabrication labor. Just plumb up a water to refrigerant HX instead of the air coil. The thing would look and operate the same indoors, but efficiency would soar due to the ground loop and water pump.

08-20-17, 11:37 PM	#7
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	Grab somebody's old 10 SEER R-22 unit off of craigs list or letgo or faceb00k marketplace and start a project. I got a goodman 2 ton heat pump unit for 50 bucks this month, and saw a few 1.5 ton units for around the same price. It is peak air conditioning season, and just as window units command a premium price this time of year, people are upgrading their existing central units in droves. They are dumping their old air handlers and outdoor units for pennies on the dollar. That stuff that runs on 240 volts is useless to most. For most, the hardest part of the project is choosing heat exchangers or building them. If you have an easy way to do geothermal, rig the loop to a plate heat exchanger rated 25 to 50 percent larger than the compressor at standard rates (2.5 GPM per ton, 10degF temperature change). If you are resourceful, you can rig a condenser out of a roll of 1/2 inch tubing inside a bucket or barrel. A moonshine worm, if you will. For 2 tons or less, 100 feet of 1/2 inch tubing will easily fit in a 5 gallon bucket. For the homebrew condenser, give it 3 GPM per ton of capacity. Voila, you're done outdoors. Sell the fan and the outdoor heat exchanger to get your money back out of the unit, or leave it in place (disconnected) to disguise what's crammed inside (small water pump and water to refrigerant HX). Indoors, run whatever you are comfortable with as a cold air source. Indoor heat exchangers can take many forms, shapes, and sizes. Just remember that the thing will be wringing gallons of water out of the air every day during cooling season. I made one out of a cylindrical air cleaner (copper tubing in place of the hepa filter) and a water heater drain pan that does a good job. It had a 3-speed fan in it, so the fan speed is controlled by the control board i put on it (read below). I sourced a TXV from surplus city liquidators for around $20. You can buy prefab fan coils or air boxes for a hefty price. The control system is easy to rig also. If you find an outdoor unit that works, you can rig the thing to a standard thermostat of your choice with a few wires and a 24VAC control transformer. Indoors, all that needs controlled is the fan, by way of a relay. I have started using the Qunda brand of control boards in my beasts. Same basic controls as a mini split unit. Cool looking indoor display/button panel that is either LED with blinky lights and 7-segment digits or backlit LCD panel. The non-heat pump controls are cheaper than the heat pump controls. The one I rigged to the air cleaner beast was like $50 off amazon. I had to add a few control transformers to work the reversing valve and compressor in the outdoor unit, because the Qunda board switches everything at line voltage. Or you can buy a mini split (or window shaker) system and save most of the fabrication labor. Just plumb up a water to refrigerant HX instead of the air coil. The thing would look and operate the same indoors, but efficiency would soar due to the ground loop and water pump.