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Heat Pump Conversion- Only Backwards

2089 Views 13 Replies 5 Participants Last post by  Bret86844
Hi All!
So that you know a bit about my experience as you read my wacky plan, here is some background on my very restricted experience in HVAC:
I am semi-retired master electrician. While active, the company I worked for allowed me to do a 2 year plumbing apprenticeship as well as a full heating & cooling apprenticeship. I have extensive hydronic experience, but my cooling work was very restricted to only a few types of systems. I only services the company's own units, not general contract work.

The only cooling systems I installed or serviced were large water cooled chillers (in the 100 ton and up range). They were R-22, R-502 or R-717. I'd occasionally service small (ca. 3 ton) R-12 & 134a refrigeration systems with multiple, remote evaporators.
As you can see, I have a decided lack of knowledge about residential cooling, hence my question here:

Summary- I'd like to convert a heat pump to normal A/C. I have found many articles about converting A/C to heat pump, but I wish to go backwards.

My home has a Haier Heat Pump condensing unit connected to a Hi-Velocity brand mini-duct system. (We have hydronic heating.) Currently it is wired only for cooling. Since electricity cost is so high, I've always ignored the heat pump capabilities of the unit. We also don't have a long heat pump capable season in Detroit. And, I have our home hydronically zoned. If we use heat pump, we won't be zoned.

System Notes-
(Terms used are when in cooling mode)
Condensing Unit- 2-1/2 ton
Evaporator - 3 ton in Hi-Velocity air handler.
Vertical coil.
Refrigerant - R-22
Metering In Cooling Mode - TXV with external equalizer. Emerson BAEB3HCA 3 Ton
Metering In Heating Mode- Fixed orifice
Protection- Filter-Driers in 3 places. Two are factory
...1) Before TXV (Field installed bi-directional)
...2) Between accumulator & compressor (Factory installed)
...3) Liquid Line, immediately before service valve outdoor. (Factory installed)
3/8 Liquid 3/4 Suction
Length = 24 feet
Compressor has a crankcase heater (Oil sump type)

The Troublesome Part:
In the unit is what looks like a distributor on the outlet of the condenser (outlet when in cooling mode). From studying the piping & piping schematic, I believe it must have the metering device & check valve for the heating mode built into it.

The problem is that this device is a 3-piece component that screws together. The bottom is where many outlet tubes from the condenser arrive, the center section I think is a seat and the top is the connection to a temporarily oversized liquid line. (3/4" here, eventually reducing to 3/8).

The only way to seal the leaks properly is to un-braze it from the distributor tubes and the liquid line. Then I would replace the o-rings that hold it together. I was able to cheat and twist the top section loose just enough to get some evil Leak Lock on the threads. But this was not a great idea because the piping twists with it. I can't braze it shut for fear of melting the metering device and/or check valve seat inside.

The custom o-rings and the part itself are obsolete.

If I am going to have to go to the work of cutting it out to repair the leaks, I may as well ditch the thing entirely and convert to straight A/C. I also get to eliminate the reversing valve which is one more place that has had leaks in the past. They, however, were easy to re-braze.

So my grand plan is to cut this out and braze up my own distributor without any check valve inside. The liquid would be gathered by the small tubes from the condenser then be sent to the liquid line in the existing 3/4" tube (which reduces to 3/8)

I wonder, however, if it will work to have a distributor on the outlet of the condenser without any metering inside? In cooling mode, it acts more like a 'gatherer' than a 'distributor'. I do not remember ever seeing a distributor on the outlet of a condenser, but my experience is quite limited with any air cooled systems.

Part Two- There is an accumulator between the suction line and the compressor. Can I leave it when converted to standard AC? I kind of like having it there to protect the compressor valves when the TXV opens wide on high delta temp days. Also note that, by design, this evaporator runs at 34-26 degrees-F, so some liquid does head for the compressor. That temp is from the air handler manufacturer. Superheat is to be between 8 & 12-F. Suction line is to be 42-F after the evaporator outlet.

Step-By-Step Plan:
A) Cut out reversing valve. Re-Pipe per normal A/C cooling mode
B) Cut out the distributor & make a new one
C) Remove the two factory filter-driers in the outdoor unit.
D) Leave the accumulator
E) Remove the bypass loop and check valve that bypasses the TXV when in heating mode. (This check valve has also been the source of leaks.)
F) Replace the indoor filter-drier at the TXV with standard one-direction drier
G) Install low ambient protection in series withe the contactor coil.

Does this sound like a workable plan?

And, if I may, I have a curiosity about the p-traps on this system.
Set Up Is:
The condensing unit liquid line outlet is 6" lower than the TXV at the evaporator.

Picturing the refrigerant leaving the evaporator, there are 3 oil traps:
A) The suction gas leaves the evaporator and travels horizontally 4 inches. It then drops into a p-trap. Next it rises 2 feet to the basement ceiling and goes horizontally about 10 feet.
B) Next it exits the building and drops to the level of the condensing unit. Once inside the unit it rises again to reach the top of the accumulator, thus making a rather large trap.
C) Exiting the accumulator, the suction line drops to the floor of the unit, then rises to the suction inlet of the compressor.
Why so many oil traps?
Is this OK to leave?

I apologize that this post is so lengthy. I wanted to supply as many details as possible for your diagnosis.
Thanks Very Much for your thoughts about this conversion & the oil traps. I certainly appreciate your advice.

Enjoy This Day!
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You can leave the accumilator i or take it out. At 8°F SH, your not getting liquid refrigerant back to the compressor.
The air is very low velocity until it exits the mini ducts. Then it goes into warp speed.
Generally inside the supply run, the velocity is over 1400 FPM, even on a restricted outlet/run. 2000 FPM is the average outlet velocity of a HV system.
1 - 2 of 14 Posts
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