By Laverne Gerard. wiring. Published at Monday, March 25th, 2019 - 10:50:56 AM.
Bob and Tim are at a job where a technician from another company could not figure out the electrical, so he just put the panel back on the electrical compartment and left the job. It is a heat pump and the compressor wiring is all loose. They need to figure out how to wire it back and find out the problem. The homeowner said the original call to the other service company was because of ice build up on the outdoor coil. Bob and Tim talked to the homeowner and explained that because the weather was cold and damp, ice buildup was expected on any heat pump in this kind of weather, but they would check the unit and see what was going on. The heat pump compressor was not running and the home was being heated with the auxiliary heat, so the first order of business was to get the heat pump operating. They went outside and noticed the ice had melted from the outdoor unit due to an above freezing day. The compressor was not running; however, the fan was running. They looked at the compressor and discovered the wires to the compressor were all disconnected, and the ends were taped to make them safe. “
Bob checked on each side of each heater and found three of the five heaters were drawing current; therefore they were heating. He said, “I can see why the system was not heating the building. It is very cold outside and will probably require all of the heaters to keep the building warm. Now, I need to find out why two of the elements are not working, and there are so many wires that I don’t really know where to start.” Bob looked at the diagram and said, “I can see that the thermostat starts the timed fan control and sequencer #1. Now what happens?”
If there is more than one zone and you are using circulators to run each zone, you use one relay for each zone. The thermostat for each zone would go to a separate relay with the thermostat for the corresponding zone connected to terminals 3 and 4. The X and X terminals from all the relays would be connected in a parallel, 24-V circuit consisting of an aquastat, flue damper, spill switch, rollout switch, and gas valve. Any separate zone would turn on its own circulator and also turn on the boiler. If the boiler reaches temperature limit, the boiler would turn off, but the circulator would keep running until the thermostat is satisfied. Another way to wire multiple zones is with the use of a multi-zone control (see Figure 14).
Bill Porter is an HVACR technician who became an inventor and a manufacturer because he found unitary heat pump wiring confusing, particularly for dual-fuel systems. He has been in the industry over 40 years. About 10 years ago, he decided to create a product that would help other technicians wire dual-fuel heat pumps with minimal guesswork, hassle, and callbacks. Porter said his universal wiring product is made with technicians in mind.
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