Variable Speed GE Profile High Suction Pressure

[clman]

Late last minute call out of area to a ncoo GE Profile. It had previously been serviced approx 30 days ago for ncoo. Owner and extended warranty co both told me that the previous servicer said unit had a sealed system leak. I found a access valve installed, ff @ 74 deg and fz @ 79. Variable speed compressor running and cool, no heat in liquid line and a slightly cool suction line. Initial low side pressure @ -4 psi. Looked for signs of leak before and after charging - nothing found. Charged unit so customer could use the unit till a resolution was achieved. The problem comes in with two things. I charged the unit to approx 3psi - No temp changes to anything. Kept going up to 5 then 10 then 15, etc till I finally got some heat in the condenser about 1/3 of the way through at 35psi. Also the compressor had a sort of dull light rod knock sound - lighter when settled and a bit more pronounced when adding refrigerant. The temp started dropping quickly then but I know somethings wrong here. I've never charged a residential unit to that high of a low side pressure before. I find it odd that the unit would have a leak and a bad compressor but I know it's possible. Just not used to charging variable speed units so it leaves me with questions that with a recip comp I would not have. Wish I would have had time to add a high side valve. Opinions please. Thanks

[tgoods]

You can't charge a variable compressor fridge using pressure readings.  Since it's variable, the pressures will change.  I'd pull all of the refrigerant out and weigh in a new charge. Then if it's not cooling, you know it's either a bad compressor or restriction.

[niobrara]

Agree with tgoods, vacuum it and install new dryer.

[clman]

I see your point. I don't know if I'll be going back to this one as the ext warr co will most likely do a buyout. I did offer to purchase it for parts should they do so so I could experiment with it. I guess moreover I am looking for more information for future troubleshooting as well as with this issue in particular. With a reciprocating compressor one would expect pressures to be a in certain parameters depending on environmental conditions. Knowing those parameters and comparing them to what is happening allows you to determine performance and faults. Certainly variable speed / liner compressors / systems should have their own set of expected behaviours and pressures which would allow you to do the same as with the recrip ones. I can't find any info on the web and nor can I find good tech data on LG's tech site.