Compressor Discharge for DHW Supplement

JStar

It's late in the season, but I want to add a HX to my condenser to make hot water in the summer while the A/C is running. Do I need to worry about making too much subcooled refrigerant, or do I need any special controls to keep the A/C system working flawlessly?

unclejohn

I don't think you can have to much sub cooling. You could possibly have to low head pressure. I think you need at least 100# difference between your suction and head. So if your running r410 and you have 130# suction then you need at least 230# head pressure.

JUGHNE

So will you bring the hot gas inside to a HX or the domestic HW outside to the Ac unit?
Did this some years at a grocery/butcher shop. Used a "Thermostore" water tank/HX. Hot gas piped inside to tank. Cond units had a head master control on outside unit, this kept steady liquid line pressure going to evap, (many pounds of R-502 at the time)
Maybe in your situation you need variable speed fan control for keeping head pressure up.

Mark Eatherton

http://www.swing-green.com

Members of the RPA, and guests for a previous HydroniX Talk talk show. Great, knowledgable folks.

ME

SWEI

Been eying those Thermastor tanks for years now. Any reports back from the customer after owning one for awhile?

JStar

JUGHNE said:

So will you bring the hot gas inside to a HX or the domestic HW outside to the Ac unit?
Did this some years at a grocery/butcher shop. Used a "Thermostore" water tank/HX. Hot gas piped inside to tank. Cond units had a head master control on outside unit, this kept steady liquid line pressure going to evap, (many pounds of R-502 at the time)
Maybe in your situation you need variable speed fan control for keeping head pressure up.

I plan to keep all water piping inside the basement. But, yes, I was going to use a refer-to-water HX. I'll trigger a SS circulator via an aquastat to circulate water through my existing tank water heater. A head master control seems acceptable. Although, I do have some leftover modulating control boards. They should work.

Is it worth putting in bypass valves to drop the HX out of the circuit when it's not needed? I'm assuming that if the circulator isn't running, there won't be much heat transfer, and shouldn't have too big of an effect on my normal condenser coil operation. Would it be okay to keep the HX in series with the compressor discharge?

JUGHNE

I believe the "Head master" control needs a liquid receiver at the cond unit. Controlling the fan seems simpler.

Don't know about the by-pass. The system I refer to had a 120 gallon tank with a 6 circuit SS de-superheater HX wrapper on outside of tank. (reminded me of a quilt). The tank had a water dump valve if it reached high temps, this would happen during the summer fairly often. (2 X 3 ton AC's...5 HP freezer...2 HP cooler).

Your 3 ton?? AC could maybe overheat your 40-50 gal? water tank pretty fast. So maybe a 3 way valve on the hot gas line is needed. Someone else here certainly knows more along that line than me.

Water to air HP's I've used have a small de-superheater for HW helper. They just shut down the pump when water temp gets to a high point. The water still can migrate by gravity thru the water tank so it is not captured inside the HX.

FWIW: One point is that the HG line brought the sound of the compressor valve pulsation inside the building. I did use the braided flex connectors at all units. The noise was not a problem in the back room of a grocery store but inside a house under the bedroom floor might be?? (2 of these units were Coplamatic's) .

Because of the distance I also should have increased my HG line by 2 sizes instead of only one.

njtommy

Fan cycling control you can get one for pressure or temperature