question about split system installs
when you install a split system lets say 3 ton heat pump and you have 40 foot 3/4 , 3/8 lineset. additional refrigerant has to be added for the lineset right. how do you know when the perfect amount of freon has been added? i had someone tell me that you just add gas until the suction lines sweats and feels like a cold can drink!! i want to know how to really know the perfect amount of freon is in the system. can someone please tell me? thanks
Not a DIY site. Call someone qualified to do this and it will save you money.
Last edited by Stamas; 08-11-2010 at 11:42 AM.
Depends on the metering device.
The old rule of thumb doesn't work at all.
If the unit is working properly and has run for 5 minutes the suction line will sweat. But it could be way over charged and burn up a compressor and or cost you dearly on the electric bill.
The manufacturer will specify in the instructions how many feet of lineset the charge is good for. And there should also be an amount per foot to add. Especially with heat pumps you shouldn't do the old tricks you can get caught and easily overcharge your system. The only way to be sure (especially in heating mode) is to weigh the charge in - honest!!! Lol and it gives you a baseline for your future reference. There is usually a subcooling number there to compare with after you get the charge right. I think these numbers are usually written in the inside panel as well.
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There's a spec in the install manual for a weighed-in baseline - for example, my Goodman system was factory-filled with enough refrigerant for 15 feet of line. with 1 1/8" line, the spec is .6 ounce per foot of line, over 15.
Originally Posted by brinkman
This spec is just used to begin the testing process, and testing and setup can vary based on the manufacturer.
To setup my Goodman, after it's been running for at least ten minutes (in stage one) , you check line pressures, delta-t, amp draw, inside supply and outdoor ambient temps and compare to that units spec chart.
Getting this right is what separates the men from the boys in this business - all of this data needs to be recorded on the repair order. If the data isn't there, it wasn't done.
If the only measurement "tool" your installer has is a cold can of beer, you need to send him home, he isn't qualified to work your equipment.
The best way to do it is to look at the manufacturers specs. to determine how much the unit comes pre-charged for. Most units come with enough refrigerant for 15 of lineset. Then find out how much additional to add based on the size and length of the lineset. Once you weigh the charge in, double check it by either checking the superheat or subcooling. A lot of manufactureres put charts inside the outdoor unit so you know what you're looking for in regards to superheat or subcooling.