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Heating, Air Conditioning, Fridge, HVAC/Damage resulting from setting the AC temp too low


I am concerned that my tenants improper use of the Central Air may have or could cause damage. I lived in the house before renting it out and had no problem with the AC. They have been there 2 years and have had to have the HVAC guy out both years. Though there were other problems that may have contributed to the problems, I believe they turned on the AC when it was still cold outside and it had freeze up. The following year I found out they had been keeping the thermostat set 65 degrees and below. My HVAC guy said not to turn thermostat below 70 degrees. The tenants wanted to renew the lease and I decided to leave everything the same (rent, etc ) but not to warrant the central air system saying I will pay for repairs but not if it goes into thousands or needs replacing. We've had two unusually hot summers and I cannot control what they do and fear that the AC unit could get ruined. When signing the lease, one of the tenants complained that they used to keep the temp at 50 degrees at their previous rental with no problems which scares me even more. Another tenant in the house said she didn't like air conditioning so I am wondering if maybe some (there are 4 tenants) are closing their doors or vents keeping things from circulating properly. I really like the people and want to please them but I don't make enough in a year off the rental to pay for new AC. Am I wrong in my fears? Is it possible to turn the air to 50 degrees without a problem? Is it true that the temp should not be set below 70 degrees? Also, I have read that it should not be turned on if outside temp. is below 55 degrees - is that correct?  I Thank you for taking the time to read this and hope to hear from you. I don't know the make of the AC and since I was not at the house and don't really understand this sort of thing, I don't have a lot of details other than the low temps that they were running the AC at.

To start with I will say this, A/C systems work on pressure/temperature(p/t)relationship.  It is a rather long process to truly understand how it all works.  A couple of common problems that occur are frozen coils and slugging compressors with liquid.  Slugging a compressor, which can occur when it freezes up, can be the kiss of death for it.  

Because of p/t is not a good idea to run the unit cooling mode below 50F-60F.  Some units might work below that and low ambient kits are installed when the need arises.

Because of p/t an a/c system is not going to run at 50 indoor temp.  The coil will freeze up long before it gets that cold inside.  There are devices that come installed or can be installed that will shut the unit down when it gets to the point before freezing up a coil. Thermostats can be installed, programmed, and locked with a passcode to prevent such a low setting.

Every system is a bit different, but 65-70 is the lower normal operating range of an a/c system based on p/t.

Closing off too many vents in a home can cause p/t issues, which can lead to failures.


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Craig HVAC Expert


I have been in the HVAC field for the past 18 years. I can help with most HVAC questions. I work on commerical buildings for the most part, and have yet to find anything I could not troubleshoot and repair, when repairable. I work on small 1 ton units to a 2500 ton chiller. Troubleshoot air flow, elect, and control problems. I attend regular classes to keep up with the latest and greatest.


I work on commerical sites, hospitals, gov't buildings. I can troubleshoot just about anything in the HVAC business.

5 years trade school, VFD training classes, Liebert factory training, some York and Trane factory training.

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