Quote:
Originally Posted by Xringer
Does an ASHP hotwater heater need two coils and two compressors?
|
Nope.
A single compressor should do it.
If you're gonna hack your A/C's, you will need to have an Air-to-Refrigerant heat exchanger for the evaporator (your A/C has this, with a properly-sized cap-tube already attached), and a Refrigerant-to-Water exchanger for the condenser (you could make a tube-in-tube or get a brazed plate HX). You will also need a small circulation pump to pump water through the condenser HX.
You could even keep the case and all, and just give your A/C a condenserectomy (newly minted word). That way you reduce your worries about hardware placement, etc.
The guy that sold me the water heater heat pump ('hydronic' is his forum name) had some issues with where to put the in-flow into the tank. He tried taking cold from the bottom, running it into the top, he also tried the reverse, and he finally settled on an in-flow pipe that ran down from the top to about half way into the tank. You could search for what he wrote, or send him a private message for details... he thought it was important for best operation.
You'll probably have some amount of frost build-up. Your A/C controller probably has a circuit for just this thing...maybe you can use it. You could also use the CAI board and experimentally derive a 'duty cycle' that would allow a lapse between on-cycles when the unit is running during the most frost-prone part of the year (whenever that is). I observed that a dehumidifier does this this kind of thing but it has some kind of a brain... but not very much of a brain.
Of course you will also need an insulated tank for a reservoir. An electric water heater would do nicely for this. I'm looking to do the same project, and I'm looking for a 60 gallon one. I'm seeing them locally for $50 to $100.
Since there's just your wife & yourself, you probably don't need super fast recovery time, so your smaller A/C would probably do it just fine. If it recovers too slow, hack the bigger one to replace.
If you use a water heater, it already comes with a high-current thermostat, and the thermal mass of the water in the tank would assure you of no short-cycling.
It will almost build itself!
If you want to be super legal, you should check to see if your state requires double-wall HX on potable water.
As always, take lots of pictures.
Have fun!
Regards,
-AC_Hacker