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Heat Pump Conversion- Only Backwards

2082 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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Error Corrections for my post, above.
In the oil trap part, there are actually 4 traps. The Item B, rises to the reversing valve. The line then drops to the floor of the condensing unit, goes horizontally a couple of feet, then rises to the top of the accumulator.

Sorry About The Goof!
Thanks for taking time to reply!

Right now the system isn't wired for heating. The stat isn't a heat pump stat, so the system defaults to energizing the reversing valve on cooling calls. (There is a DPD switch on the condensing unit circuit board for such installations. Nice touch by Haier.)

My thoughts for doing the A/C only conversion are because the distributor (if that is what it is called) has leaked twice and can't be properly fixed. Sadly, it is obsolete.

The only way to keep that thing from leaking forever would be to remove it, gut the rubber & plastic parts out and brazing it into one piece, thus making it a distributor, but backwards. It collects liquid from the condenser through several small tubes. In cooling mode and stuffs it into one, liquid line heading for the TXV. (In heat mode, it works as a distributor and metering device.)

The check valve at the TXV has leaked, but that's easy to solve with a one-piece magnetic one. And, the reversing valve has cracked at joints twice so far, so it isn't the most reliable of components either. (But my re-brazes have held well, so it might be OK now.)

To summarize, all the heat specific components are troublesome.

So I figured, perhaps wrongly, if I am going to all the work to pump the unit down & cut-out the distributor for a braze up, I may as well also ditch the reversing valve & TXV bypass to turn the condensing unit into straight A/C.

The fastest & neatest solution would be a new condensing unit, but I'd like to save some money if I can. A new A/C only condensing unit will cost about 1,000.00 for a dry ship unit. Or, I can replace the lineset, p-trap and TXV to go with a 410a condensing unit. But, my hesitation there is getting all of the mineral oil out of the evaporator.

So, if it is possible, my plan would stop the reoccurring leaks by removing the troublesome components.
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Thanks All for your thoughts.

The system held at 450 microns for 4 days (copper only- no hoses). I put in a charge of dry nitrogen. Today, at 48-F ambient I have 152 PSI. I'll be interested to see tomorrow what my pressures look like when it is about the same temp outside. But when refrigerant is in there & it is vibrating around- who knows if my cob-job repairs will hold up?

I'm confident the reversing valve will be OK. The check valve is probably solved with Leak Lock (even though using that stuff, to me, is like giving up). But the crazy distributor thing has me nervous.

Right now, since money is a bit tight, I'll probably use it as-is. I will watch pressures and the sight glass. At the first sign of trouble, I'll recover the refrigerant and make the dollars-or-time decision. I'm kind of like you, User12345a, I usually would rather spend time than money. (Unless it is car repair. I'm really crummy at that stuff.)

First thing I'll do is get a sample of oil. If there is the least bit of acid, it is "Good-bye Haier". No sense spending time on something where the compressor is on its way out. The condensing unit is old ans is indeed Chinese (but has a Bristol compressor). I had the chance to work on a Goodman last year for a friend. It looked surprisingly well made and was quite easy to service.

Thanks Beenthere for the accumulator information. Glad I can leave it if I do the conversion.

Thanks Again All. I'll be sure to post when the machine is either converted or changed out. Hopefully it will survive this season & not lose any more green gold (R-22).

Enjoy This Day!

PS: I very much enjoyed reading your house remodeling pages Bret. I'm inspired! (Maybe...)

Good call on the MC cable!
I just did a little favor job for a good client and used MC in the person's garage along the face of a header. The owner questioned the decision. (Since I worked industrial all those years I default to conduit, but $$$ were a justifiable concern.) Three days later I was back to replace some existing NM (Romex) that was next to the new MC. He hit it with something he was storing in the rafters & cut the cable.

With MC, remember to use the little red anti-short bushings. I've done many service calls where they got skipped & a conductor eventually cut itself on the jacket.

I hope the rest of your projects go very well. The photos look great!
(They should go smoothly since you guys already got the nail stepping on over with. My wife & I did the same thing a few years ago. We both got new foot holes and tetanus shots on the same day.) So much for clean as we go...
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Thanks Supers05 for the explanation about the distributor and the advice to replace the evaporator if I go with 410a. (Probably should)

This evaporator is unique to the Hi-Velocity brand system, so I'll check the cost Monday (just so I have all of my costs in line before I make the fateful decision).

Caution! Potentially Boring Stuff Ahead....
The evaporator is kind of cool, actually. The vertically installed, multi row coil is 16 tall, 19 wide and 4" thick and has very tightly packed fins.

This thick evaporator, coupled with the fact that the air is momentarily held in the unit, dehumidifies like nothing I've ever seen. On a rainy day, you can watch water drain in a thick, steady stream. The wet/dry bulb readings are fun to watch, too (If you're really trying hard to get out of doing more important stuff.)

By 'momentary held in the unit' I was referring to how this mini duct system causes the air to get jammed into a large evaporator/holding chamber before exiting to the comparatively small main duct (50 square inches). By doing this, the air is in contact with the evaporator longer than with traditional systems. I guess 'Hi-Velocity' is kind of a misnomer. The air is very low velocity until it exits the mini ducts. Then it goes into warp speed.

On the not-so-good side, the major components are OEM style & custom dimensioned. But the indoor unit has been 100% reliable so far. The fan motor is still original even though it has been running 24/7 for at least 10 years. I installed an infinite range speed control in our hallway so we can conveniently adjust the fan speed to suit. On a call for A/C the fan goes to high speed. On a winter call for humidity, the fan goes to a different preset level of my choosing.

Kind of spiffy until I get too senile to service it. Then one of you guys has to deal with my over-engineered control system. (Fear Not! Schematics and text explanations are posted on the unit, dork that I am.)

Thanks Again to everybody who helped out with advice. I'll now be quite comfortable when the repairs fail & I have to make a decision.

Be Sure To Enjoy This Day!
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