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Fire and Ice
14-01-2008, 05:25 AM
Recently while working on a roof top unit for a walk in cooler, I came across the question of wether to charge or not to charge. R-22 *****. Ambient air outside @ 23 degrees. Hi side @ 155#. Lo side @ 12#. Sight glass is full. Cooler room temp is @ 39 degrees. Unit seems to recover rather quickly. I suspect a slight low charge. What would you do?
thanks-Fire and Ice

nike123
14-01-2008, 08:56 AM
I would measure superheat, subcooling and temperature difference of evaporator and condenser, also compressor current and discharge temperature.

The MG Pony
17-01-2008, 02:07 PM
I'm with Nike, I'd audit the system then determin where to go from there with certainty.

Is it cappilery tube or txv, this will tell you the most usefull messure.

Evap clean and all that sort of thing?

Gary
17-01-2008, 11:56 PM
Why do you think it needs more refrigerant?

Gary
18-01-2008, 12:10 AM
Only at the two extremes (grossly undercharged and grossly overcharged) does the amount of refrigerant in the system have anything to do with the head pressure.

Between these two extremes, the head pressure is almost entirely determined by the temperature and volume of air flowing through the condenser.

On a cool day, the head pressure is down. On a hot day, the head pressure is up.

Increase the airflow and the head pressure is down. Decrease the airflow and the head pressure is up.

Head pressure (aside from the extremes) is not about charge.

Josip
18-01-2008, 12:31 AM
Hi, Gary :)


Only at the two extremes (grossly undercharged and grossly overcharged) does the amount of refrigerant in the system have anything to do with the head pressure.

Between these two extremes, the head pressure is almost entirely determined by the temperature and volume of air flowing through the condenser.

On a cool day, the head pressure is down. On a hot day, the head pressure is up.

Increase the airflow and the head pressure is down. Decrease the airflow and the head pressure is up.

Head pressure (aside from the extremes) is not about charge.

Very nice and clear.....

Best regards, Josip :)

Josip
19-01-2008, 04:29 PM
Hi, MRcoolingMAGIC :)


Why supprise ,Gary is one of the top guys in our refrigeration field.Thanx to him and O'Brien we can learn something ,that the books can not offer.:D

:confused::confused:....it is in the books for sure, but you have to read many many books to extract it in the way Gary did.....simple and clear....

Best regards, Josip :)

Gary
19-01-2008, 07:14 PM
Hi, MRcoolingMAGIC :)



:confused::confused:....it is in the books for sure, but you have to read many many books to extract it in the way Gary did.....simple and clear....

Best regards, Josip :)

Many many books... or one of Gary's books. ;)

Josip
19-01-2008, 07:56 PM
Hi, Gary :)


Many many books... or one of Gary's books. ;)

:):) why not, but my statement is ok....not only one book, but books ;)

it is not easy to write down all, in only one book, I know that.....

Best regards, Josip :)

The MG Pony
19-01-2008, 09:09 PM
what is the name of your book gary? It was once on Xtreme systems but the name has drifted off forever into cyber space!

I'd be interested in it.

Peter_1
20-01-2008, 12:03 PM
See the man's signature

Gary
20-01-2008, 04:00 PM
Or click on this link:

https://www.merchantamerica.com/tmethod/

The MG Pony
20-01-2008, 08:11 PM
Ya I noticed that a bit after posting the question, thank you gary.