4 Ton Weather King Heat Pump

[jah]

I installed a 4 Ton Weather King heat pump and matching AHU. It was installed in July, so we set up the charge in the cooling mode. It worked great. I get a call in Febuary that the thing is not working right. I check it out and the compressor is dead. So I replace the compressor and set up the charge in heating mode. I checked the cooling mode and it was low. In short when the charge is right in heating it is to low for cooling and when it is right in cooling it is too high in heating. Any one have any ideas?

[BaldLoonie]

10 SEER? 12 SEER?

The 10 SEER uses a TXV outdoors plus a charge compensator. It is tricky to charge to make both seasons happy but with a matching indoor coil we haven't found any we couldn't get right. The 12 SEER seems especially picky. We tried to put a couple of them on coils meant for older model WeatherKing 12 SEER heat pumps with no luck.

[Wild Leg]

Static regain?

[Shophound]

In short when the charge is right in heating it is to low for cooling and when it is right in cooling it is too high in heating. Any one have any ideas?

I may have a few ideas.

First of all, how are you determining the charge on this system? Weighing in? 126 degrees over ambient on the compressor discharge while in heat mode? Superheat and subcooling? Beer can cold?

Look at the OEM's specs for factory charge on the nameplate. Measure length of lineset and equivalent length of all fittings. Determine if charge needs fine tuning from OEM's factory charge amount.

Ensure air handler has adequate airflow in both heating and cooling. Clean filters, clean coil, all supply registers and dampers open fully, etc.

Check lineset to ensure it is properly sized for the system's tonnage and length of run.

Without using superheat and subcooling readings when charging in cooling mode, you're only guessing as to what the charge might be. Pressures tell only part of the story. Going by pressures alone typically leads to an overcharge. That may have been what wiped the compressor.

[docholiday]

So give details...

Model# for OD unit, ID Ahu and coil, psiton or TXV? Line set length, size and vertical seperation, airlfow(actual), any other details. We can tell but there are several things you should look for.

[jah]

Here are some of the details. I do not have model numbers with me at the moment, but I will give you as many details as I can and post the numbers later. It is a 10 Seer 4 ton HP, 4 Ton AHU (04882), #82 piston indoor, Line set is about 15' 1"1/8 X 3/8. AHU is about 5' higher than HP unit. This HP unit has a scroll compressor and outdoor expansion valve. Originally charged the unit by superheat in cooling, but did have some problems getting it in range. When charged in heating mode recently went exactly by the directions and chart inside the unit panel.

[jah]

I should have mentioned the air flow situation. This AHU is a downflow with the duct in the crawl. We have 10 8" flex duct supplies coming off. The longest of these is 35' and the shortest is 5'. The unit supplies a small church auditorium. The return comes through a wall and is wide open.

[bornriding]

sounds like your system does not have an accumulator. To charge this system, you would have to 'short' the cooling cycle a little to compensate for the heat cycle. But neither cycle will be its most efficient.
I have a Lennox unit, same deal, only they loke me to service it twice a year so I just adjust the charge each time, for each cycle.
There's not going to be a perfect way of doing it.

[docholiday]

There is indeed a proper charge but everything else has to be right, this is a heat pump and for that reason the match and installation must be correct.

Looking at the data, it calls for a TXV indoors when matched with a 4 ton WK hp even in 10 SEER. Also, how is the return run, is there a large return plenum? If it comes in with a tight turn you can be missing part of the coil. You should have 8 slabs in that coil (4 a's). If its tight consider turning vanes.

You also need to know your actual air flow, not calculated by duct design. Might I suggest using the heat rise method.

Also can you recall if the flaps were folded out on the air handler at the plenum? If they werent, thats about a 25% airflow reduction. You may have to pull the blower to see, but you can do that when you install the TXV.

Your lines sound ok.

[BaldLoonie]

Imagine that, it does! We've never installed a PJ heat pump that big so didn't realize they called for a TXV. Those cube pumps have been such a pain in the #$# to us with their crazy coil matchups and problems in the outdoor unit.

[jah]

There is no sharp turns in the return plenum. It actually goes into the drop ceiling space and a 30 X 30 grill on the wall.
I don't see that as a problem, but I did wonder about the TXV. When I asked my distributor about it they told me that I did not need it, but like you I think it is probably where the problem is.
My next move was to put a TXV on the indoor coil and change the 3/8 line to 1/2. If you say the 3/8 is ok I will just start with the TXV.
I know the flaps are folded out. In fact, the distributor told me that I could not just set it on a box that extended into a plenum into the crawl, but I needed a 10" straight flange off the AHU flange in order to generate the proper air flow. I didn't see how that mattered, but I did it as they said.
I will check the heat rise, though. That would be a good information check.

[docholiday]

Dont put a 1/2 in line in, that goes against the instructions also.

When you add the TXV, do this....

Recover the refrigerant, dont pump it down. Add the TXV and then add the drier. Tripple evacuate. break with nitrogen the fiorst two times and then refrigerant on the third. Weigh in the charge per the label.

[docholiday]

Originally posted by BaldLoonie
Imagine that, it does! We've never installed a PJ heat pump that big so didn't realize they called for a TXV. Those cube pumps have been such a pain in the #$# to us with their crazy coil matchups and problems in the outdoor unit.

The 12 SEER requires the TCQC coil too, no option for the multiflex.

[dash]

The flanges on those air handlers?

I hear different views,anyone have the correct length of duct that should be the same size as the flanges?


Thanks

[docholiday]

You trying to perpetuate rumors also?

You're a Carrier man, read thier instructions too. Do I need to go over this static regain garbage again? Maybe I'll start a post discussing this in its entirity but it will just crop up again so it seems moot.

No, the air handler we are talking about has flanges that are folded down for shipping unlike the Carrier which are up from the factory. They are to be folded up when the unit is installed. Many times, if the plenum is installed over the whole top, which I dont have a problem with, the flaps are often forgotten is my point.

In this case, I am merely suggesting the airflow be verified. If it is found to be low, then fix the problem if it is not low, then apparenly the duct system is satisfactory.

[Edited by docholiday on 03-29-2005 at 10:24 AM]

[BaldLoonie]

dash, the I/O manual suggests 3' from the blower outlet, but if that isn't possible says "even 6, 12 or 18" will help". It says not doing that way and hooking plenum to outside dimensions of the air handler means "as much as .1" static pressure will be lost."

A product manager told me 5+ years ago that line of AHs were gonna be history soon. I guess 5+ years ain't soon enuf in his view

[dash]

Thanks Baldie.


One more question,I saw an older model Rheem ,that had "perfs" for tabs that could be bent up,not only around the blower discharge,but the outer edge of the cabinet top, as well.Can't imagine,why they were "perfed"on the edge of the cabinet top??



I've asked our techs ,and no one ever sees the duct the size of the blower discharge,and we they find the Tabs left down the majority of the time.


They know the airflow is low,but the static is also low ,as the blower has less static capability with the tabs down,and large duct.Low ESP,normally indicates good air flow,but this tab and duct size thing,changes things.I think we need to discuss this more with the techs and do a little testing.

[Edited by dash on 03-29-2005 at 10:49 AM]

[docholiday]

Originally posted by BaldLoonie

A product manager told me 5+ years ago that line of AHs were gonna be history soon. I guess 5+ years ain't soon enuf in his view

They were, replaced with the BHC.

See my static regain post.

[jah]

Thanks Doc, for your help. I have ordered a RXCPRXCT-CHL. This the part that my distributor said was for the 4 Ton WK unit that I have been dealing with. Does this look correct to you? I ask because you seem to know more about this equipment than they do. They said they would have it in for me in 4 WEEKS!?!

[Edited by jah on 03-30-2005 at 03:32 PM]

[docholiday]

Since we never really didn't establish the model number, I will say for a 10 SEER, 4 ton, yes its an RXCT-CHL