ReplyRestricted return, or low supply air flow???
52 degree suction line, it isn't freezing due to a refrigerant issue.
Regular Guest
Im working on a 5ton r22 ac system with a txv, the suction pressure is at 32_33deg saturation, subcooling is at 12°, and superheat at 20°. The indoor temp is around 68°(becaise the customer wants it that cold for their wine). It has an 18"and a 10" return, and 6tons of supply ventilation (haven't checked the static but im assuming that its ok). Is r22 not meant to operate in that low of a load, because when I take the cover off the blower door and suck in warm attic air my saturation goes up to 40°.
Professional Member *
Restricted return, or low supply air flow???
52 degree suction line, it isn't freezing due to a refrigerant issue.
"If history repeats itself I am so getting a dinosaur"
Regular Guest
Return looks good, I took the covers and filters off and it changed nothing.
Regular Guest
Supposedly it has worked fine for years
Banned
I think that is normal ,considering you are on the verge of refrigeration. The lo side load is low so the suction should also be lower. Does the evap freeze over?
Regular Guest
Hasnt yet but with the saturation bordering freezing im afraid it will. Im almost tempted to open expansion valve a hair to bring it up a little
Banned
Check the existing SH , leave it at normal.They might be lucky enough to have enough "off cycle defrost" just like refrigeration.
Professional Member*
Why were you called out? It probably has run like that all the time, since what they are doing is basically a refer unit.
UA Local 32 retired as of Jan 2020
Professional Member
How much wine do they have? sure seems like a waste of a 5 ton unit
Banned
Drink enough Ripple Wine and you will see a waste
Regular Guest
I was called out due to a compressor burnout, replaced compressor flushed lines and noticed system has no filter dryer and no screen before piston. Afyer replacement turned sysyem on and my suction was way low, about 45_50 psi and icing up. Cleaned cpndenser coil and debri of condenser fan motor. Ran again, and could not get my suction psi up, or superheat down. So I suspected a plugged cap tube, so we replaced coil. Now my superheat is better and suction stauration is better but still not were I would like it.
Professional Member*
Check for a dryer inside the cond. unit. It may be plugged.
I miss you mom and dad.
Professional Member *
OK. Your Entering the Freeze Up Zone. (tv pun intended)
You have TXV trouble.
When you enter the Zone,you must rethink your Basic's.
You HAVE to Increase your SH,Starve the Evap,lower Charge(in our case),Adjust CFM.
We did this on an Old RUUD Gaspac with Captube's.NO piston or TXV.
I would go after the TXV and if it was adjustable,Check to see if it's been molested..
Not sure how far I can go Here at times so I'll leave you with this adv.
No matter how long you have been doing this,
Go back and reread the Basic's.You WILL Learn something.
Why is it called,an Act of GOD when IT has Nothing to do with Him?
Will of the Devil would be more appropriate IMO.Just Saying.
PSALMS, 18 & 25.
I am Tired of High Efficiency Propaganda.
Professional Member *
OAT? Indoor wet bulb? Temperature drop?
Yeah, I know, this is a TXV, but low load/low temperature is going to bring low suction pressure under certain circumstances. This is medium refrigeration after all.
Regular Guest
Oat was 75, wet bulb65, did not get temp drop across coil, but differential is 18
Professional Member *
When you mean differential, are you talking about the difference between return and supply temperature? If so, that would be your temperature drop.Originally Posted by claysontech
Assuming airflow is perfect at both the condenser and evaporator, I would say low load is the problem. 68 degree return is very low and if there isn't a lot of moisture in the air, that can cause your low side saturation temperature to drop below freezing. This doesn't necessarily mean the coil will freeze over because if there's a lack of moisture in the air, there's nothing to freeze on the coil. You might see some light frosting, but it's perfectly normal considering the conditions.
My only other thoughts are you might still be low by 1/2 a pound or so. Some systems operate with subcooling as high as 14 degrees, so 12 degrees isn't high by any stretch. Once you start getting above 15 degrees, then you may have an issue.
Keep in mind residential systems aren't in controlled environments, so it's useless to split hairs in some cases.
Regular Guest
I really appreciate all the feedback.
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