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Question DetailsAsked on 5/24/2017

My sub cool is 2.8 and the units required sub cool is supposed to be at 11. Should I worry?

The techncician came out today and told me it was like running a car with no oil which is pretty serious. Unit is 2 1/2 years old. The gauges showed my sub cool at 2.8 and he said the units required sub cool is supposed to be 11.

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Don't know what a sub-cool is - did you mean a sub-zero reefer maybe ? Don't know what the 2.8 versus 11 number is either - AWFULLY low to be refrigerant pressure, which is normally around 50-100 psi static and well over 100 into the 300 range on high side when opearating.

You also did not say WHY you called the tech - was this for pre-season servicing and he checked the pressure as part of that and noticed it was low, or because it was not working normally ?

Oh - I bet he gave you pressure readings in bars - not psi. So 11 would be around 160 psi - into the common operating pressure for home A/C systems, and 2.8 would be about 40 psi - on the quite low side even for static pressure for most systems.

Certainly you should worry if the pressure is well below design level - because the refrigerant carries the lubricating oil around with it, so if you lose enough pressure there is not enough gas flowing to keep the lubricant going to the compressor, which will burn it out, like he said. I presume he recommended recharging the system with new refrigerant ? Or did he go for broke and recommend replacing the entire system, or the compressor at least ?

If your unit has been cooling (albeit maybe slower than normal, or running a long time to do it) I would guess you have a leak that needs finding and fixing (and should not be the evaporator coil, which hopefully has a 5-10 year warranty on it), but if it has been cooling and the compressor has not been making a lot of noise (squeeling, whining, gasping, thumping commonly), I would guess it will probably be OK once the correct gas is injected to bring the pressure back up to normal.

One thing you can do - during the recharging process, since it sounds like much of your gas has escaped anyway (assuming the TXV regulating valve malfunctioning and giving bad operating pressure is not the problem), would be to have him evacuate the system and remove the filter/dryer canister and see if the lubricating oil in it is clean looking, or if it is badly burnt and scorched. (In some systems that can be done without draining the system, by shutting off cutout valves). That would be at least an indication of how serious the situation might have gotten.

Looking at the compressor and the tubing in and out of it and painted parts can also be indicative - if the tubing is badly heat discolored or paint is scorched and burnt (other than where soldering flame might have hit it) then that would be an indication of pretty significant overheating, which might make you trend towards compressor replacement.

You will have to determine what confidence level you have in him - probably highest if he explains the options and possible consequences without jumping straight to giving you a price for a total system replacement. I would guess, if he looks at the filter and sees it pretty burnt and dirty, that he might suggest flushing the system (a very good idea if dirty is the case) and a good tech, if the oil is burnt, might say something like your compressor is likely pretty scorched inside and might die well before its normal say 10-15 year life, but that it is your call whether to see how it does after flushing and recharging, or to minimize the risk of an unexpected breakdown by replacing the compressor after flushing the system. There are cleaning chemicals made or reocmmended by the manufacturers that run through the system while operating to fllush out burnt oil and carbon and such.

If the filter does not look bad, then personally I would get it recharged and see what happens - might well go for another decade or more and not have experienced any signfiicant problems.

Of course, dig out you original warrnaty - because depending on where the leak is, it might or might not be at least partly covered by the warranty.

Answered 3 years ago by LCD

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