Bob and Tim are on the second day of an inspection of an apartment house building that has multiple split-system heat pumps. They have inspected all 60 outdoor units on the roof. They are now going to inspect the indoor units.

In this troubleshooting situation, the equipment you’re servicing is a 240-volt, single-phase split system in a small office, and the customer’s complaint is that the system is blowing warm air.

Bob and Tim have arrived at Tim’s first service call. Tim asked Bob, “What is this call all about?” Bob said, “This is a new customer that wants us to take over the maintenance work for this apartment house.”

In a previous article on chilled water systems we focused on maintenance of the “heart” of the system, the chiller.

Btu Buddy has met Bob for lunch to answer some questions that Bob had about yesterday’s service call. Bob asked, “Why did that motor have two contactors and so many wires going to it? It seemed very confusing. I am glad that I tagged those motor leads when I disconnected the motor. I never would have figured out how to reconnect the leads.”

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.