Carrier 7.5 Ton Heat Pump

[heat fixer]

I have a Carrier 7.5 ton Heat Pump that suffered a severe burnout. I was really careful in the compressor change following all recommendations from Copeland on clean up,etc. It is a Scroll compressor and when I went back to start it up after charging by weight with R-22, the suction went to zero and the head pressure was unchanged,holding steady at 50 psig. The suction pressure goes back to 45 psig when the system is cut off. Cant run it long because I dont want the scroll going into a vacuum I m thinking a blockage somewhere but dont really know where to start. Looking for some other opinons to help me figure out where to begin. This is a 10 year old unit and compressor number 2. Trying to prevent compressor number 3 from occurring.

[dandyme]

does this thing have a model #?

does it have a solenoid somewhere?

is there a txv?

where did you get the charge weight from?

[heat fixer]

Model # 38ARQ008-501
Indoor TXV which was replaced about 3 years ago
No solenoid that I know of
Got charge from data plate on unit

[SBKold]

Are you running in heat or cool?

What was the amount the nameplate's calling for? I thought they only had a holding charge listed.

[jtrammel]

Commercial equipment is field charged so unless the installer marked the charge (which I wouldn't trust) it is only a holding charge. Packaged units are fully charged though.

[heat fixer]

2.8 lbs r-22 it may be only a holding charge i thought it seemed really low but i cant get the unit to take anymore gas either i thought the low pressure switch would not open if it was too low.

[welling service]

This is a 3 phase unit I assume. Have you checked the rotation? If the suction goes to zero why can't you add more gas? 2.8 pounds is no where near a full charge.

[dandyme]

1-might want to look around that IDU for a solenoid valve.

2-how long is the piping?

3- suction =0 & head=50?????is that correct?

4-just how much r-22 did you weigh in?

[captaincallback]

Did you also change reversing valve, liquid drier, and contactor?

[hands]

Is this a RTU or Split System

[vahe501]

2.8 lbs r-22 it may be only a holding charge i thought it seemed really low but i cant get the unit to take anymore gas either i thought the low pressure switch would not open if it was too low.

Sounds like the unit has a LOW charge, 2.8 lbs R22 is way low on a 88,000 BTU unit.
The Data sticker reads 2.8lbs R22 that is the charge the unit was shipped with, the Normal operating charge is around 20lbs.

[vahe501]

This is a 3 phase unit I assume. Have you checked the rotation? If the suction goes to zero why can't you add more gas? 2.8 pounds is no where near a full charge.

You have to charge the unit wile it is running on the suction side. Be Cautious not everyone can do this....