copland scroll

[savoc]

I always end up with the worst jobs. Today i worked on a old emailair ducted A/C with a copeland scroll zr 72.

discharge temp 125 degrees Celsius.
discharge pressure 1500 kpa.
suction pressure 450 kpa.
suction temp at compressor +25 degrees Celsius.
ambient temp 30 degrees Celsius.
room temp 26 degrees Celsius.
temp difference across return and discharge air 8 degrees.

First thing i did was reclaim gas, vac,driers and charge with new gas(r22). the pressures and temps stayed the same. The suction line leaving the indoor coil is sweaty and super heat is ok cant adjust vavle. but by the time the cold gas recharges the comp the suction line temp has reached +25 degrees. hence the high discharge temp. The lines are fully insulated. Is it possible that the line are to long approx 40 meters? Could an over sized suction line cause this? I belive the a/c is way undersized. Any clues would be helpfull.

[AlexG]

21K superheat is too high. Lack of refrigerant or txv is not adjusted...

[texas64]

You should replace the TXV. Then check. Please don't do any adjusting on the new TXV. You should consider blowing out the system with Nitrogen before installing the new TXV. You didn't give the liquid line temperatures, but you did good by eliminating the filter and any problems with contaminated R22. At least you can't have a possibility there.

[texas64]

Oh, this old system has been around with this piping size, I don't think it would have made it to "old" if the size was wrong or the length too long. I have piped multiple over 200 feet long line sets and the systems work flawlessly. Of course there were some increases in pipe diameter, though.

[savoc]

i was hoping it wasnt the txv. but all signs point to the vavle. its in the worst place possible.

[Brian_UK]

Is the TXV strainer blocked?

[paul_h]

What is the sub cooling?
With such a low HP, either all your refrigerant is in the liquid line (TXV or any other strainer blockage, or TXV fault), or the reversing valve may have a problem (just saying RV because of high LP, though it's not really that high for the ambient, it is higher than a liquid line blockage would make it be, so worth looking into RV temps too rv suc in, rv suct out, rv dis in, rv dis out)

edit: also, what charge did you give it? Factory charge (if so did it give data for how many grams per meter?)
Did you weigh out the old charge to give you an idea of what was in it?


edit:
If life has taught me anything, it's two things, always weigh out the reclaimed charge, and take photos of everything in the job, that is all...

[texas64]

I was considering how you were saying that the TXV was going to be a pain to replace because of its location. Since this unit is really old, why don't you remove or cut out the TXV and braze it outside the unit. You could run the liquid line directly to the back of the TXV and just insulate the leaving side of the TXV as it enters the unit. Your torch time would probably be less if you are only making one weld inside at the distributor. Just an idea to save time and maybe less hassle. ;)

[zanit1]

salut to all
c'est ma premiere participation.
pour essayer de repondre, je trouve que le taux de compression est faible (1500/450), d'un coté de l'autre 125 °C pour le refoulement c'est trop a moins que la temperature exterieure est elevée.
svp donne nous la temperature exterieure pour verifier les mesures effectuées.
je crois que le probleme est au niveau du compresseur (soit il tourne dans le sens contraire "scroll"??? ou mauvaise compression)...juste une idée.
amivalement

[zanit1]

hello to all
this is my first participation.
To try to answer, I think the compression ratio is low (1500/450), on one side of the other 125 ° C for delivery is too saw the outside temperature is 30 ° C.
1500 Pa at the condensation temperature is about 42 ° C.
the distance between the discharge and the condenser is it important?
becaufe of repression 125 ° C to 42 ° C ...... the problem is his first.
I think the problem is the compressor (ie it rotates in the opposite direction "scroll"?? or bad compression) ... just an idea.
friendly

[Mick13]

mate i think the compressor is the cause of your problem....

hard to say without being there, but if u say the superheat is good at the end of the evap, where the txvalve bulb is placed, then the txv is doing what it should. it maintains its superheat at the bulb, not at the compressor.

whats the liquid line temp?

the unit probably doesnt have a sightglass, but if it does, is it full?