Bob and Tim are discussing the job that they are about to start. They are at a residence and the system has a blown low-voltage fuse. Tim said, “Let’s just change the fuse and try it and see if the system will start up. The only thing it can do is blow another fuse."

This troubleshooting problem involves a 5-ton, R-22 rooftop air conditioning unit, and the customer’s complaint is that on days when the ambient temperature exceeds 90°F, the system doesn’t keep the store, which was recently remodeled, comfortable even though it seems to be running continuously.

Bob and Tim arrive at the jobsite of a new customer. The customer is the owner of a shopping center that has a branch post office as one of its tenants. The complaint has been that the system is not controlling the indoor temperature in the postal facility. Tim tells Bob as they are arriving that the service ticket says that they are to service a 20 ton split system that uses a hot water coil for heating and an air conditioning coil and condensing unit for cooling. They are to do routine maintenance on the entire system.

In this troubleshooting situation, the customer is complaining that their comfort cooling system isn’t performing as it should. Their description of the problem is that the house always seems to be too “sticky”. They also say that the problem seems to be especially evident when the outdoor ambient reaches its highest level in mid-afternoon.

The outside temperature was 40°F, not really cold for the season but the humidity was high in the air. Moisture had just seemed to be laying in the air for several days. Bob and Tim were called to a residence which reported a frozen heat pump. They arrived and talked to the housewife and she said, “My heat pump outdoor unit is a solid block of ice. When I look at my neighbors outdoor heat pumps they don’t look like mine. I think something is not right." They all went to the window in the dining room and looked down on the heat pump outdoor unit and sure enough it was loaded up with ice.

This troubleshooting situation has a history. In the six years that the up-flow gas furnace in this three bedroom house has been in service, several attempts have been made to solve the problem of one bedroom that, according to the customer, is always too cool during the heating season. This residence is a brick home on a slab, and the air handling system, which located in the crawl space above the ceiling, is shown in Figure One.

Bob and Tim are on air-conditioning system service call, and the system has a persistent leak. It seems to leak down about once a month and has to be recharged. Several technicians have tried working on the system and cannot seem to find and stop the persistent leaking. Their service order says to says to repair the leak using whatever methods needed to be used. This persistent leak must be stopped.

This month’s troubleshooting situation involves an up-flow gas furnace that serves as both the heating source in the winter and as the air handler in a split system for cooling in summer. The condensing unit is on a pad next to the building on a concrete slab. Since there is no crawl space or basement, the connecting tubing and wiring for the condensing unit are routed through an underground chase from the equipment room to the outside.

Bob and Tim are on their first service call for winter. They are at a retail store that has 4 units to heat and cool the store. They are all 15 on heat pumps. One area of the store is not heating or cooling well and during the heating cycle, the heat pump auxiliary heat light is staying all for long lengths of time.

The equipment in this month’s troubleshooting problem is a forced-air electric heating system with five resistance-type elements, and in order to ensure that this equipment can operate with maximum efficiency and prevent an electrical system overload on a call for heat, a multiple-step sequencer system employed.