Continental reach in
Working on a continental reach in cooler today. R-134A got there today found suction pressure at 16 no high side tap. Unit wouldnt pull below 45. So decided to recover charge and put high side tap in pull vaccum recharge to factory. New reading 24 suction 150 head. Unit pulled down to 38. But what has me bafffled is I had like 44 degrees superheat. I have a sneaking suspicion it is restricted at cap tube.
How old is the unit? Any kind of maintenance on the unit? 24 psi at what box temperature? What's was the ambient temperature and what's the subcooling? Discharge temperature?
With 134...its a very good possibility it's restricted. You could have easily checked for restriction when you had the system open. Put nitro through the high side and see how fast it equalizes. You could also back blow the system with nitro to try and clear the restriction. That seems to work pretty well sometimes.
Did you change the drier too? And if you did...did you remember to flow nitrogen while brazing the captube to the drier?
Don't mean to bombard with all the questions...it's tough to diagnose over the Internet lol.
At any rate....it sounds restricted.
High side was 150 had 7 degrees subcooling. Didnt not change drier know i should have. Blew through with nitrogen but didnt noticed like it cleared a restriction or anything.
I really need to apply for a pro membership. I could really get into a lot more detail on my approach in diagnosing.
Try blocking the condenser and see what happens to the low side. You could also add a few more ounces and see how it reacts. But 150 psi is starting to get pretty high for 134 depending on the ambient temp.
Was it 24 psi at a 38 degree box? Did you measure 38 degrees in the supply or return of the evaporator?
But by the sounds of it....I'd be quoting out a new captube and drier.
most of these fractional HP systems have the cap tube soldered or taped to the suction line for heat transfer. This makes it impossible to take an accurate superheat reading at the compressor.
For the what it's worth it agree. System sounds ok if it pulled to 38. Possibility of a leak if it was running at 16 and then 24 after the factor charge was weighed in?
Originally Posted by craig1
If this system has the factory spun filter it could be clogged as well. Seen it many times.
Originally Posted by HVACTECHND
Use a CO32-Capt filter/dryer by Sporlan which will give you a high side port. Also sometimes if you cut the first few inches off the cap tube that is where the restriction is.
If the cap tube is welded to the suction line, I have not seen much difference if you don't create the heat exchange again by connecting it to the suction line when you replace it. Just make sure you get the exact right size. You will have to call the manufacturer or the supply house that handles that brand.
Sounds to me like it was low on charge. Because really all you did was charge it... If cap tube is clogged, pressures would've still been low.
He did say that he had 44°superheat.
Originally Posted by trippintl0
Could still be partially restricted.
Like others posted, make sure you don't have any heat exchange like cap tube wrapped around an accumulator or cap tube strapped to suction line, if you're going to look at superheat for diagnostic purposes.
For me, at 24# suction with a confirmed nameplate charge, I would not suspect a clogged cap tube. If you had low suction pressure, then weighed in charge and still had low suction, I would suspect a restriction. If weighing in the charge corrected it, is seems that the charge was the issue, that's just my way of thinking. But of course, as JoeMach said, anything as possible, could still have a partial restriction. Thats why most of us hate those cap tubes, all they ever do is clog up!
As a side not, I have observed many Continental's run higher suction, possibly due to larger evaporators or maybe undersized compressors, than say, a True cooler. On True I usually see like 16# suction, but on Continental I usually see around 20 - 25. Although I honestly don't work on that many Continentals, seems more of our customers have Delfield or True brand.