noncondensibles?

[ajram]

On rtu's what are the symptoms for non condensibles, I know that you will get High cond. pressure, but what else should i look for

[master mechanic]

HOOK UP YOUR GAUGES TO SYSTEM, RUN THE CONDENSER FAN WITH- OUT THE COMPRESSOR FOR ABOUT 10 MIN. CHECK DISCHARGE PREASURE AND CONVERT TO TEMPERATURE COMPARE THIS READING TO OUTDOOR TEMPERATURE. IF THE TEMPERATURE OF THE SYSTEM DOESN'T CORRESPONDED WITH OUTDOOR TEMPERATURE + OR - 2, NON CONDENSABLES ARE PRESENT

[dhaynes]

went to look at a unit the other day, and my pressures would go from 55 psig, clear up to 70, then back down again....the discharge seemed to correspond in the same way...unit is about 5 yrs old, is this a sign of noncondesables also?

[micdundee]

"pull em down! pull em down! WAAAAAAAY DOWN !!!

[dhaynes]

so do u agree there is air in the system dundee? i didnt install this system but it looks like they didnt pull a good vacuum.

[maxster]

a sure sign........flashing sightglass and a hot LL with all the fans running and the compressor loaded up.even if the SG is clear pull some liquid out to break the glass and see how much the LL temp changes if at all.

[dhaynes]

also i forgot to add that my ambient that day was 83, and i tried the trick of taking the comp. out of the circuit and comparing temp with the press while the fan runs......my temp ended up being 74, i thought the pressure would be higher than the o.d. temp if it had non-cond. in the system

[captinsano]

A quick and easy check is to take ambient temp then take liquid line temp and if it is below ambient you have alot of air.Liquid line temps will normally only approach ambient by 5 degrees air will give you a false subcooling reading.Thenpump down run fans and let sit for 1 hour check codenser saturated temp and it should be equal to ambient if higher air and nons.A sight glass is the most inproperly used device on a system @ low load @ temp with proper charge you may see flashing, as unit loads subcooling will increase see what each manufacturer recomends for subcooling @ full load.You put 10 degrees @ low load you will be overcharged @ full load.
Hope this helps break out the gauges and thermometers forget the sight glass about the only thing they are good for is a mouisture indicator

[kevink1955]

Back in the OLD DAYS we used to recover the charge then check the pressure vs temp of the recovery cylinder. If the pressure was higher then it should be we would very slowly bleed off the noncondenables from the top of the cylinder till the pressure/temp relationship matched

I do not think we where venting any refrigerant, only the non condensable gases. Do you think this is still acceptable under current EPA regulations?

[dhaynes]

i went to a training seminar once, where the instructor explained how to bleed the non-condensalbes from the recovered refrigerant but it has been too long ago to remember exactly how to do it. i remember it being a fairly simple process but time consuming as well

[wallatech]

The non-condensable tend to end up at the top of the condensor or top of the reciever tank. I have gotten them out before by opening discharge vavle and letting it blow hard for about 5 seconds,any more and its freon:).Other than that i would pull it out evacuate the system,use micron gauge, and weigh in fresh charge,also change drier.

[dhaynes]

guess i have to apologize for not letting u know that the symptoms i am describing are occuring on a residential split system. wrong thread i guess, but should still apply right?