R407 C wall mount LG 7 Kw

[Abe]

Need an insight into this one. Last year installed an LG Wall Mount, 7Kw Cooling only R407C

In my opinion it was never as cold as I thought it should be, I put it down to the gas. never mind.........got a call today, unit is struggling

I hooked up gauges, back pressure is settled on around 2.7 Bar..........then condenser fans cut, I hear a whooshing sound as if a solonoid has opened..........back pressure zooms up to +8 Bar..........condenser fans cut back in and back pressure starts going back to 2.75 Bar again

After a while compressor and fans stop...............after a while restart again

Any ideas anyone??

[Gary]

I am assuming this is an A/C unit?

This sounds like a defrost cycle.

Have you taken a full list of temp measurements?

[chemi-cool]

Hi Abe,

I agree with Gary. If it goes into defrosting cycle when its hot out, check the charge. Another problem that I would check, is the evaporator coil temp sensor. You should check its resistance to see if it is function OK. That sensor is responsible of defrost in cooling mode.

Another thing that comes to mind. Does the compressor works all the time?
You say its cooling only so there might not be a 4 way valve in the condensing unit.

Chemi

[Gary]

Given the low back pressure/low SST (about 21F), I would say the sensor is just doing it's job.

[chemi-cool]

Yes Gary, but if its cooling only unit then I doubt if there a 4 way valve to preform the defrost.

Faulty compressor comes to mind, the sound Abe describes is a scroll stopping and starting.

Chemi

[Gary]

A full list of temp measurements would clearly tell the story.