5 Ton GSHP Build

[randen]

Nearly finished with the re-build. The refrigerant side is still holding the vacuum. The water circuits are near completed. Everything has fitted nicely into a compact package. A little more solder and a pressure test then a trial.


The stainless housing needs a little more work but as it is the unit could be tested and then the housing cover can be installed. Oh but the pipe insulation will go on as well.

This compressor is a 3 phase which we have a invertor to drive it. That seemed to work so well, soft start and different run speeds. Although I didn't have a lot of time to play with it. The operational power requirements did look promising.

Soon I'll have some more details. Looking forward for the air-conditioning side as this is probably an overkill area for capacity. As seen with our home heat-pump. One day I had set for maximum cool and after 5 hrs the house was at 17 Deg C. Upon my wife's arrival from work she wasn't impressed with the exercise. " I hope its not going to stay this cool"

The photo's are of the previous configuration with a tube in tube HX (not enough surface area for the evaporator) The BPHX are a little oversized but it worked out to a more compact package.

Randen

[NiHaoMike]

Easy solution: just dial back the frequency setting (and voltage) on the inverter. Or more realistically, do that with a variable output thermostat. A good operating range is 40-65Hz, with the limitation that the high end will be limited by the compressor current rating. Which basically means that if the evaporating and/or condensing temperature are high, you'll likely reach the rated current of the compressor before you reach the high end, at which point you don't want to keep going. Conversely, if conditions change and the current starts going over, you'll want to throttle back the frequency so the motor doesn't overheat.

On a package unit like yours, it's highly unlikely that oil return would be an issue, especially with plate exchangers. Thus there is no need to have a timer to do an oil return rampup.

[jeff5may]

Originally Posted by stevehull

Jeff,

I have been thinking of doing this with my open loop GT heat pumps (precooling return air with water) for summer AC

My well water temp is about 60F and I can get a real cheap evaporator (that doesn't leak) to put before existing GT heat pump air coil.

When the unit is on, it uses ~ 5 gallons per minute (~ 40 L/min). Easy to plumb the water exiting this precooler to then go to the GT heat pump input. I bet the water temp is now a few degrees higher, which means a lowering of the EER.

Clearly, I am not going to get any latent water removal, but it should pre-cool the return air. Return air is about 80 F or so.

Do you think the time/trouble is worth it? Or am I trading just one efficiency for another . . . .?

Thanks . . .

Steve

You could run both coils in tandem off of your well pump. Then both the heat pump and the pre-cool exchangers would see the same source temperature. Some fiddling might be needed to balance the flows, but imho it would be worth it. Don't underestimate the power of 60 degree water to yank lots of latent humidity (and sensible heat) out of the return air.

If you felt daring, you could rig up a control that would adjust the flow automatically. As your heat pump ramps up, the pre-coil could do more gpm. At a certain setpoint of discharge water, the control could feed more water to the heat pump, increasing heat flow and COP.

Just running source water through the pre-cool coil while the heat pump isn't running (at reduced cfm) could also save energy. Unless your source water is very close to return air temp, then all bets are off. But knocking 5 degrees per pass off of your return air for the cost of a water pump and a blower running on low could prove to be very economical.

[stevehull]

Jeff,

What water GPM (going through the "precool coil") would you suggest? Assume inlet water temp of 60, air temp of 75, with about 400 cfm going through this exchanger.

I was thinking of starting with 1 GPM and seeing what the outlet temp (water and air) were.

Steve

[AC_Hacker]

Originally Posted by randen

Nearly finished with the re-build. The refrigerant side is still holding the vacuum. The water circuits are near completed. Everything has fitted nicely into a compact package. A little more solder and a pressure test then a trial.

Randen,

That's a beautiful machine you have made.

I can't wait to find out about the performance data.

My only possible concern would be with the copper tubes that attach to the compressor, and the possibility of stress fracturing. It may not happen at all, but if such a problem did occur (it happened to jeff5may), introducing some J-loop into the copper path would be an easy remedy.

Way to go!!

-AC

[randen]

AC_Hacker

Thanks for the heads up. Didn't think of the possible resulting fatigue of the copper tube. I felt the generous loops in the first iteration would have been OK as the scroll compressor runs very smooth and with the VFD. The ramp to start/stop eliminates a lot of the torque rotation normally seen with a contactor closing/opening the circuit.

But the thought of a heads up and a fatigue crack happening without due diligence would be upsetting to say the least. I really do appreciate the input!!

It only took a few extra minuets to make the change. The vacuum is holding again so I will proceed again with the water circuit. All the copper is cut and fit.

Still some cold nights so we should get a good idea to what the heat-pump will be capable of.

Randen

[AC_Hacker]

Originally Posted by randen

...the thought of a heads up and a fatigue crack happening without due diligence would be upsetting to say the least. I really do appreciate the input!!...

Excellent fix.

I think you're clear for take-off!

Keep us posted...

Best,

-AC

[randen]

I though I would bring you up to date. The water side of the heat pump has been completed however it had wrestled me to the floor. Pressure testing showed three weepy threaded couplings on the BPHX. The difference of Chinese NPT and north American threads had reared some ugliness. The tapers were not exactly right. I could only thread them on about 3-4 turns. Unsolder/clean threads use liberal amount of silicon threaded pipe dope, re-solder test. I had used the Teflon tape and a small amount of silicon on my previous attempt.

Houston we have no more problems. Its holding pressure beautifully.

Oh one tip -I was looking around for a bubble type solution for detecting the leaks. Happened on my little boys bubble blowing bottle complete with wand. Worked extremely well with the added glycerin.

Randen

[randen]

Still not out of the woods. Two fitting still leaking. Found the issue. Chinese Male Pipe Thread on the BPHX don't quite match north American Pipe threads. Who knew.!!

Standard north American Pipe threads 1" 11-1/2 threads per inch.
Supplied Chinese pipe threads 1" 11 threads per inch CLOSE !! Only out 1/2 a thread!!!but will not seal!!

I guess I'm turning out tailored fittings.

Sorry guys, Really wishing now at this point,I had just bought a heat-pump!!

Randen

[jeff5may]

Sorry to say, but this is a common problem nowadays. The NIMBY ppl had most of the steel foundries in America shut down, so now most iron pipe and fittings come from China. Even the fittings that are the right thread leak out of the box. Anything painted or galvanized MUST be chased out before fitting, or you will be doing it after the fact. No amount of pipe thread dope will cure lazy machining.

The production maintenance men were fighting the same thing today where I'm working. A hydraulic punch press blew its high pressure bypass valve yesterday, and they air-mailed a (chinese) replacement valve in overnight. Part came in at 9AM, and they jumped right on replacing it. By 10, they were ready to try it out.

The first punch the machine made, one of the (original) pipes slipped a thread and oil went EVERYWHERE! No problem, right? Wrong! They were still trying to get the unit leak-free when I left at 4:30. The area had a berm of cat litter poured in a circle around it to keep the oil pond from growing. Root cause: replacement part was painted and had crappy, painted threads out of the box. Everyone was in such a hurry to get the machine running that they didn't thoroughly inspect the new valve. Cuz a factory authorized part should work, right?