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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 7582
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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My compressor is shutting off while the handler keeps

Customer Question

Hi! My compressor is shutting off while the handler keeps running. It is only happening when outside Temps reach ~100f. Water mist on outside unit keeps it on. I've had a tech out 3 times this week. 1st trip found low refrigerant but he couldn't replicate problem. 2nd trip he replaced the fan motor. 3rd trip same day he replaced the high pressure switch. It is still doing it and he's coming back in the morning but I'm already $800 into this. I don't want to be mad but I'm almost out of money to fix this. I have a York but dont know the model. Any suggestions?? Thanks, T
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.

Hello,

Tell me about how old the unit is... and if you have used the water hose to clean the condenser coil or not by forcing water between the fins of the condensing unit coil.

It may have a clogged condenser, or it may have been over charged with refrigerant.

We can go from here without any time limits.

Customer: replied 1 year ago.
It's about 10 years old. Yes, I clean the condenser coil pretty often especially this time of year with the monsoon-dust storms.
Expert:  Phil replied 1 year ago.

Thanks,

This technician is not particularly incorrect at all, his guesses were valid. However if he had verified the compressor discharge pressure with real or simulated 100+ weather he would have known whether to replace the high pressure cut out switch or not.

Since he may not have done that, and if he or someone else had worked on the system before this problem began, it is quite likely that the system is over charged with refrigerant, especially if it is a heat pump, and was worked on the winter.

Let me know about all that, we can go from there without a time limit.

Customer: replied 1 year ago.
The prevailing theory is that there is a partial clog in the refrigerant line and that was causing false pressure readings. He said this unit has a strainer where the refrigerant is distributed through the outside coils. He said there's another at the expansion valve on the inside unit. Thoughts??
Expert:  Phil replied 1 year ago.

Hello again,

No clogg what so ever in the refrigerant lines will result in high head pressure. That is a very common misconception... based on the idea that if the refrigerant flow is restricted, refrigerant GAS will back up into the condenser coil and cause the high head pressure.

However, in the condenser coil the hot gas is *condensed* into a liquid, the volume then shrinks and the head pressure actually *drops*

There is one fairly rare exception... that is when the condenser is a *micro channel* type instead of a tube and fin type.

Here is a video on the topic... tell me if you have a micro channel type coil or not.

https://www.youtube.com/watch?v=Q0VhglEz_as

Watch this video above first. Micro channel use has since been discontinued by a number of system manufacturers.

https://www.youtube.com/watch?v=-cJtnSsuUSA

In that case, your tech has about a 20% chance of being correct. (that is a 1 in 5 chance) in his view that there is a restriction in the refrigerant liquid line.

You can tell by inspecting the condenser on your unit if it is micro channel or not... if it is not micro channel, then your tech in this case is a little short on training and experience and he or someone before him has over charged your system with refrigerant.

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