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Originally Posted by tim79 Wait till the spring or you will end up doing it twice. Can't always wait till spring. What if the RTU cools a critical area? It is just something we have to deal with north of the Mason Dixon Line.
Wait till the spring or you will end up doing it twice.
Using a recovery machine is a good option, but you should have it connected to your charging hoses and pull a good vacuum on it to remove any moisture first.
Originally Posted by gwoner Use your recovery machine and weigh in . Works every time 3 votes for this so far ,,,,it's what I do ,,,,and by the time you dick around with cardboard and bags,fire ,hit water (we had a guy blow a jug up doing this ),having to drag them on/ off the roof ,dispose of it or save it ,,,its just as easy and probably faster to pump it in with your machine ...
Use your recovery machine and weigh in . Works every time
He has to weigh the charge in. But I will use that cardboard to block the condenser
5 gal bucket with hot water. 30 lb jug fits right in there.
Carefully cycle outdoor fan motor by hand ?
.....back in the day with r12 we had heaters(electric) that went on a 30# drum and Robinair (are they still in business) had a charging cylinder that had a heater in it. But all that is a little over the top!
Originally Posted by rcac101 Take a large plastic garbage bag and wrap it around the condenser. I usually let the fan hold it in place and charge the system its quick and easy. Hard to find a big enough garbage bag for a Rooftop Unit. That trick works until it gets really cold.
Originally Posted by hands They would probably do the same if you were caught with a control panel open and you didn't have your PPE gear on, but that never happens either does it. you are correct
Take a large plastic garbage bag and wrap it around the condenser. I usually let the fan hold it in place and charge the system its quick and easy.
Originally Posted by mikeacman that works... A lot of the places I service would politely escort you of site and never allow you to return if caught putting a flame to a pressure vessel .... They would probably do the same if you were caught with a control panel open and you didn't have your PPE gear on, but that never happens either does it.
Sell them an economizer?
Originally Posted by hands If the system was evacuated to 500 microns or lower, You should be able to get most of the charge in without even starting the unit. I will use a torch to warm the refrigerant drum if it won't pull in the entire charge by itself. You could also use a heat gun if you have one, but a MAP gas torch works great. that works... A lot of the places I service would politely escort you of site and never allow you to return if caught putting a flame to a pressure vessel ....
If the system was evacuated to 500 microns or lower, You should be able to get most of the charge in without even starting the unit. I will use a torch to warm the refrigerant drum if it won't pull in the entire charge by itself. You could also use a heat gun if you have one, but a MAP gas torch works great.
Wow down here 20f is cold I say let's drink some coffee and charge it next summer That trick is a first for me I sure hope I never have to use it
Originally Posted by mikeacman To add ,I use my recovery machine to recharge units . I can weigh it all in before I even start the unit up.... After all ,its a refrigerant pump.... Mike is right. That is how we do it in cold weather. Awful hard to create enough head even with blankets and cardboard when it is below zero. Which means that we wouldn't be able to work on them all winter. So we put the weighed charge in with the recovery machine, then start it up. Never fails, we always have to go back in the summer and trim the charge or adjust the TXV, but it gets us close. Sucks doing AC work when it is below zero.
To add ,I use my recovery machine to recharge units . I can weigh it all in before I even start the unit up.... After all ,its a refrigerant pump....
You do have to weigh it in However you may have to block condenser to keep head up so the suction will stay up so you can get system to take charge without it cycling on freeze stat. Using cardboard to block entering air to the condenser usually works great
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