In this troubleshooting situation you have inherited a service problem that goes back to last year’s cooling season… residential HVAC equipment that’s seven years old with a lot of history, and repeated trips in response to complaints that this split system that employs a horizontal, attic-installed gas furnace “just won’t keep the home comfortable.”

Bob got a call to go to a convention center where the air conditioning system was not working. It was a 75-ton unit with one compressor. The system was many years old, but had been functioning fine, until now. After checking out the unit, an ohm check showed 0 resistance to ground.

A variable frequency drive (VFD) fails to vary the discharge-air fan speed. A motor overheats and fails prematurely. While each troubleshooting problem in an HVAC system presents its own unique set of circumstances, HVAC professionals may recognize such problems as possible power quality issues.

Bob has received a call from the dispatcher about a system that is not cooling. The job is a small building with a 5-ton cooling unit. Bob went to the outdoor unit. It was running and all appeared normal. He went to the truck to get his gauges, and when he got back, he noticed that the compressor didn’t seem to be running.

This month’s troubleshooting situation involves an under-counter refrigeration unit in a commercial application. The first technician explained to the customer that the compressor needed to be replaced. After that technician left, the customer called the office to request a second opinion.

Bob has been sent on a service call where the customer is complaining about her power bill. She thinks that the heat pump may be the problem. Her power bill is much higher than last year. She explained this to Bob and he started by asking a question, “Does the auxiliary heat light come on very often on your thermostat?”

Air conditioning coil cleaning is an important air conditioning maintenance procedure that sometimes takes some patience, and usually takes a lot of water. First, you have to make some common sense evaluations.

Bob and Btu Buddy were on a service call yesterday where the compressor motor was running overloaded due to internal load; the bearings were dragging or worn. Btu Buddy told Bob, “Motor overload protection and circuit protection are subjects that need to be discussed later.” They’ve gotten together today for that discussion.

In this month’s troubleshooting situation, our customer has called to say that the older package unit that heats and cools his office is managing to warm up the area, but then seems to cool down too much before providing heat again. When you arrive, the first thing you note is that the indoor blower motor is operating, and you check the fan switch setting on the thermostat.

Bob got a call from the dispatcher to go to an office building that has a 3-ton heat pump compressor that has been shutting off after startup. The fan would continue to run. The building maintenance man said that he had observed the shutting down of the compressor several times.