Rooftop commerical Lennox AC compressor keeps tripping on the internal breaker

[dchou4u]

Our office has a rooftop Lennox THA090 AC unit. It comes with 2 compressors. Almost everyday we have to go to the roof to restart the compressors because they often will trigger an internal circuit breaker that protects the compressors. According to the PCB board that is next to the compressors, when it trips the breaker, it says it is because of a High Pressure fault (LED1 will flash, and LED2 will be ON solid). What would cause this fault on a daily basis? Thanks for any tips!

Here are some pictures of the AC unit:

[Mark]

1) use a clamp on Ammeter to verify that the current is indeed high 2) use a pressure gauge to check the high side pressure to see if is indeed high 3) check that the condenser coils air flow is not blocked or dirty and that the condenser fans are running correctly

Mark

[The Daring Dufas]

Are there bubbles in the sight glass when the units are up and running after 5 minutes or so? Another problem could be dirty condenser coils. A low charge or dirty coils could cause the compressors to overheat. ?

TDD

[bob haller]

might be a bad breaker, circuit breakers are designed to get more sensitive at end of life......

[Stormin Mormon]

The high limit switch is designed to protect the compressor from burning out, when the amperage or discharge pressure is too high. When it trips, you're supposed to to call a HVAC service company to come out and repair the unit. If you press the reset and do it all over again (the next day), eventually you will have a compressor burn out. And the resulting repair will be several times more expensive than having the unit serviced. Talk to the people in the stores near you, see who they use, and who does a good job. Your cheap approach is going to cost you mega bucks before too long.

Christopher A. Young Learn more about Jesus

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Here are some pictures of the AC unit:

[Stormin Mormon]

They totally need to call a service company, and have it repaired. Before the compre$$or burns out. That way, they can have the unit serviced for a couple undred, instead of compre$$or replaced for $$everal thou$$and dollar$$.

Christopher A. Young Learn more about Jesus

.

1) use a clamp on Ammeter to verify that the current is indeed high

2) use a pressure gauge to check the high side pressure to see if is indeed high

3) check that the condenser coils air flow is not blocked or dirty and that the condenser fans are running correctly

Mark

[Mark]

if the guy didn't already know and had to ask what to do on a newsgroup, then you are probably right.

Mark

[dchou4u]

Thank you all for the tips. We will call a service tech to come and check it out.. :)