Condensor to Water conversion

NRT_Rob

We are aware of people using brazed plate heat exchangers to turn a condensor into a "chiller", along with a buffer tank, flow switching, etc.



I am wondering... is there any reason we couldn't source a "top coil" indirect water heater, and pipe the refrigerant to the top coil, and do the same thing? this would eliminate several service items and significant cost, I believe. but I'm not sure how the refrigerant would like it.



I imagine the critical detail would be in selecting the temperature hysteresis and operation range to make sure you get the heat rejection you need to keep the compressor running and happy. but maybe there is more consideration than that?

SWEI

Refrigerant heat recovery

I'm not 100% sure what you're looking for, but would one of these work? http://www.thermastor.com/Heat-Recovery-water-Heaters/

NRT_Rob

no

I'm trying to take a regular outdoor condensor unit and make it a chiller for chilled water applications like radiant cooling etc.



right now the upcharge to go chiller is pretty large... mostly because of the much, much lower volume of such units in production and all the testing etc required to sell them.



a cost effective method of utilizing more typical outdoor condensors would reduce the cost of chilled water systems.

Rich_49

Rob

are you wanting to produce Heating cooling combi radiant systems ?

NRT_Rob

we already do

with heat pumps. looking for a way to extend this more cost effectively to people who have more traditional heating equipment like boilers. or with larger cooling demands.

Rich_49

What

would be the sequence of operation you are contemplating Rob ?  Have been thinking about all matter of different stuff lately

NRT_Rob

well

I imagine it would be something like



1. thermostat places cooling demand

2. energize tank cooling aquastat

3. when aquastat requires heat rejection, engage condensor

4. when aquastat is satisfied, turn off condensor.



ta daaaa!



if we do it with a heat exchanger external to our buffer tank, we have to use flow switches and an extra pump, plus a lot of install labor. thus the question about using a copper coil in the top of a tank...

SWEI

Not sure where the tank comes in

but you can get flat plate HXes rated for refrigerant.  As long as they are properly sized, they should be able to be hooked up to a conventional A/C outdoor unit.

NRT_Rob

for chilled water

a major benefit is being able to decouple the load from compressor operation and do real zoning. so a buffer tank is necessary to ensure adequate runtime from the compressors in most cases. inverter driven compressors can help but then it's a control issue I can't easily solve... they don't take 0-10vdc signals as of yet that I'm aware of...



but with external HE we have to prove flow before we let the compressor run, and it requires the HE, pump, flow switch that are not required if we put the HE *in* the tank like a top coil would achieve.



so if it works,I'd vastly prefer a top mounted coil in an indirect as a heat exchanger for this setup. drop a failure-prone flow switch and an energy-using pump and two major vectors for failure that could damage the compressor, plus a lot of assembly time and labor and wiring.



but I don't know if refrigerant will like that... the unit on the outside, the condenser, is basically a big coil of copper so I think it should work?

Limamikemike

Refrig to water exchanger

http://www.aquasystemsinc.com/

How about these?

NRT_Rob

hmm

those are intriguing but they don't seem to have that much water content so we'd still need to have a buffer tank to ensure proper runtime of the condensor. good people to talk to though I bet, thanks for the link.