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We’ve got alot of smart people here, hopefully someone with some real good HVAC experience. This is my first experience with 408A.
Had a walk in freezed break down at work. The filter/dryer rubbed against the suction line unitl there was a hole. I fixed the tubing and, since I’m just about out of R502, decide to switch over the the 408A replacement.
Evacuated the system, ran a vacuum pump for about an hour. Charged with 408A into the high pressure side for several minutes. then started the system up and continued to charge through the low pressure side.
Bubbles in site glass dissapeared but I’ve heard that that’s not a real good indicator with some of the replacements. This thing has a pretty big receiver on it so I figure charge isn’t that critical so I kept charging for a few more minutes.
The system ran fine all night. The next morning, there was ice on the evaporator and suction lines. Maybe low on charge?, added alittle more refrigerant. A few hours later, it’s short cycling because the high side pressure safety keeps shutting it off after a few seconds running. I adjusted the pressure stat thinking I could force it to run just until the temp in the freezer was down to 0 degrees but even at 400lbs, it still shortcycled.
So, I figured I had overcharged it. It was a couple of hours before I was able to get back to it and by that time it was running smoothly except that the evaporator and suction lines were icing up again. I’m going in to check it this morning.
I’m lost. I thought 408A was a drop in replacement for 502.
Replies
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We've got alot of smart people here, hopefully someone with some real good HVAC experience. This is my first experience with 408A.
Had a walk in freezed break down at work. The filter/dryer rubbed against the suction line unitl there was a hole. I fixed the tubing and, since I'm just about out of R502, decide to switch over the the 408A replacement.
Evacuated the system, ran a vacuum pump for about an hour. Charged with 408A into the high pressure side for several minutes. then started the system up and continued to charge through the low pressure side.
Bubbles in site glass dissapeared but I've heard that that's not a real good indicator with some of the replacements. This thing has a pretty big receiver on it so I figure charge isn't that critical so I kept charging for a few more minutes.
The system ran fine all night. The next morning, there was ice on the evaporator and suction lines. Maybe low on charge?, added alittle more refrigerant. A few hours later, it's short cycling because the high side pressure safety keeps shutting it off after a few seconds running. I adjusted the pressure stat thinking I could force it to run just until the temp in the freezer was down to 0 degrees but even at 400lbs, it still shortcycled.
So, I figured I had overcharged it. It was a couple of hours before I was able to get back to it and by that time it was running smoothly except that the evaporator and suction lines were icing up again. I'm going in to check it this morning.
I'm lost. I thought 408A was a drop in replacement for 502.