OK, you’ve exhausted all of the existing air from an interior space; now how do you replace it? You bring in makeup air from another source. For the purpose of an HVAC discussion, your source will be mechanical equipment — makeup air units.
Potential or “voltage” relays are used with single-phase capacitor-start/capacitor-run motors, which need relatively high starting torque. Their main function is to assist in starting the motor. Knowing the sequence of operation for this type of starting relay can help you diagnose, confirm, or rule out certain service problems.
There are four pieces to the refrigerant system diagnostic puzzle: suction pressure; high-side pressure; superheat; and subcooling. This article talks about subcooling.
The big push is on to replace R-22 unitary air conditioners and heat pumps, and it looks like the industry has really and truly decided that R-410A systems are “it.” This article offers an overview of some of the issues related to R-22 and -410A in the field: operating pressure differences, oil characteristics, and temperature glide.
Following up on Howard Leonard’s October 10, article, “Hidden Problems Can Cause Carbon Monoxide,” Leonard elaborates on the discharge side of the combustion air system, the flue.
One of the main functions of the condenser is to condense the refrigerant sent to it from the compressor, but desuperheating and subcooling are other important functions.
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