View Full Version : charging in the winter
03-09-2005, 07:40 PM
installing ICP 7.5T two-stage condenser on roof of mall; MUST have running by tomorrow. It's freezing in New England; I have never charged anything in the cold before, so I need alot of help.
03-09-2005, 07:52 PM
turn crankcase heaters on. keep condener fans off charge by subcooling after pressures start getting into range enable condenser fans. recheck subcooling and hope u have a load
03-09-2005, 08:41 PM
I am not familiar with your model number, but I assume this is a split since you have to field charge. What you have do, as Servicefitter wrote, is charge the machine as if it were a designday. You could kill the fans, or, more easily, block of the condenser coil with cardboard to elevate your head pressure during charging. If you are running R22, get your head pressure up to about 250 psig. This would simulate running on a very warm day if you are installing a high efficient unit. Ensure that at this range you have a clear glass and measurable subcooling and you will be in the "ballpark" This being said, if you hava an entering air at the evap much below around 60 degree wetbulb, you have very low load. This can hamper your charging. Keep a close eye on this start up of suction superheat, especially with a low load as stated above. Do you have a TX valve? This will help some but if mechanical refrigeration is required (no economizer) you are going to HAVE to install a means of head pressure control. You may be able to get by with a fan cycle switch, which in relation to liquid line pressure, brings condenser fans on and kills them when head dips. Good luck
03-09-2005, 09:01 PM
Charge by weight, total up line lengths charge per installation instructions. this isn't a closed book test the answers are in the book and if you do it by the book you will CYA.
03-09-2005, 10:35 PM
Weight is without a doubt your best choice. If you are not able to come up with the correct amount, there is another way. Now keep in mind this is not exact & certainly not my normal method of choice. When I'm in a situation like this & in a hurry, I will do somthing real close to 2-3 lbs. per ton[depending on line length] & slip back by on a better day & check on it. Good luck.
03-09-2005, 10:37 PM
Bucket with warm water let er rip
03-09-2005, 10:45 PM
2 stage, is it a scroll, or bristol(TS) compressor.
Head control on the bristol(TS) compressor isn't a good thing, might void warranty.
If you call ICP, and tell them the line set length, they can tell you the amount of charge needed.
03-10-2005, 07:51 PM
I agree that weight would be best bet
But, if weight cannot be established. Do as r-404a said & block the condenser coil ( at yur temps, may have to disconnect fan also ) until head pressure is around 250 - 275 psig. Then I would set system charge for a 20 degree delta 't' across my air handler, check superheat & verify that it is above 5.
Then come back when warmer & recheck
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