HVAC system stops taking refrigerant during charging
Retrofitted or low-pressure systems often stop pulling in refrigerant prematurely while running, leaving the unit undercharged and freezing up the expansion valve. This happens when suction pressure drops too low to keep the compressor running or allow the remaining charge to enter the system.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1charging through the low side while the unit is runningDid this help you?
- 2verifying line and tank connections for blockagesDid this help you?
- 3clearing and pulling a fresh vacuum before rechargingDid this help you?
- 4turning off the breaker for 10 minutesDid this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“Attempted to convert a r22 3.5ton Lennox system to 422b, unit takes some charge but it stops taking it and when running unit freezes txv because of under charge but still won’t take it in.”source ↗
“New tank on my scale it only took 2lbs then i sat there for 10 mins running the unit it just wouldn’t take it”source ↗
“Obviously there is low r32. That's why we're trying to add more. But how tf can we when it won't run the compressor?”source ↗
Where this came up
People with this problem also raised
- 5Can you just refill a leaking HVAC system with refrigerant to get by?
- 2How to get air bubbles out of the cooling system
- 4Why does my new ice maker only fill with water once?
- 13Why do cooling coils keep freezing over?
- 31Refrigerator and freezer stopped cooling completely with loud humming noise
- 2AC unit humming with no air coming out of vents