Why must the pressure relief valve on the liquid receiver of an R-22 system never be capped or plugged?
Safety · EPA 608 Type II. The correct answer, and the reasoning behind it.
Hermetic compressors under vacuum and other high-pressure hazards.
The question
Why must the pressure relief valve on the liquid receiver of an R-22 system never be capped or plugged?
- It lets air into the system during evacuation
- It is used as a charging port
- It protects the receiver from bursting in a fireCorrect answer
- It meters liquid into the evaporator
Why “It protects the receiver from bursting in a fire” is correct
A relief valve opens to release pressure before a vessel can rupture, for example if the receiver is exposed to fire or overheating. Capping or plugging it removes that protection and turns the receiver into a potential bomb.
Source: EPA: Test Topics
Why the other answers are wrong
- It lets air into the system during evacuation — A relief valve is not an air inlet for evacuation.
- It is used as a charging port — Relief valves are not charging ports.
- It meters liquid into the evaporator — Metering liquid is the job of the expansion device.
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