Max ambient temp for AC compressor

kurt mitenbuler

Would anyone know where I could find the recommended or spec'd maximum ambient air temperature for a residential split system type AC compressor?

Reason being, I looked @ a condo building where all the compressors (42 total) are located in a single small masonry box. The air temp in the box was >130degF. There was no engineer; don't ask me why. We're trying to figure out how this could have happened.

One of the unit owners asked what the max temp should be. I didn't have an answer offhand. Anyone?

Eugene Silberstein 3

How high is too high?

Although there is no published maximum temperature, it is safe to assume that systems will function when ambient temperatures are as high as 120 degrees F. This, of course, does not imply that the systems will work well.

The temperature of the air that surrounds the condensing unit has a direct effect on the system's operating pressures. The systems's operating pressures have an effect on the compression ratio of the system, which is a major factor in determining system efficiency.

For a standard efficiency system, the condenser saturation temperature is about 30 degrees higher than the outside ambient temperature. In your case, if the ambient temperature is 130 degrees, the condenser saturation temperature will be about 160 degrees. If you look at a pressure/temperature chart, you will see that the highest temperature on the chart is about 155. So, without going any further than that, it is safe to say that 130 degree ambient is above the limit that anyone would like to see.

Putting that aside for the moment, the systems as they are presently installed are definitely costing the equipment owners a boat-load of money to operate. Opening up the cage and providing some mechanical air movement through the area should help alleviate the problem.