Impossible Head Pressure?

[hydra]

Short story: Original Pressures -7/150. Added 6-8 ozs 134a to a 1/3 HP true prep table. Suspected low charge. Head pressure shot to 700! I'm not kidding, 700 and it kept running. Quickly bled the charge to 400 and it kept running. My final diagnosis is capillary restriction with non condensibles. My question is: 1) Has anyone seen pressures like this in hermetic units? 2) Why did it not trip on internal overload?

[lynn comstock]

Short story: Original Pressures -7-25 deg F /150 116 deg F . Added 6-8 ozs 134a to a 1/3 HP true prep table What is the system rated charge?. Suspected low charge. Head pressure shot to 700! I'm not kidding, 700 and it kept running. Quickly bled the charge to 400 and it kept running. My final diagnosis is capillary restriction with non condensibles. Sounds like a good possibility since it prossibly has a low side leak but may be a totally blocked metering device. My question is: 1) Has anyone seen pressures like this in hermetic units? Only once, long story. 2) Why did it not trip on internal overload? Shot up quickly and if the metering device is totally blocked, the compressor motor is moving zero refrigerant and therefore is not doing much work. It would eventually overheat.

Also, Do you know the history of this equipment and how much it may already be overcharged? Isn't this fun?

[hydra]

Also, Do you know the history of this equipment and how much it may already be overcharged? Isn't this fun?

No clue. First time working on this unit, but it's getting a new cap tube and drier on Friday. Will leak check as well.

[hydra]

Also, Do you know the history of this equipment and how much it may already be overcharged? Isn't this fun?

No clue. First time working on this unit, but it's getting a new cap tube and drier on Friday. Will leak check as well. The fun never stops with this job!