By Romana Maurice. wiring. Published at Tuesday, March 26th, 2019 - 05:57:38 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.
The importance of understanding and using wiring diagrams to troubleshoot refrigeration systems cannot be overemphasized. Most system problems can be divided into two broad categories: electrical or mechanical. However, the majority of system problems are electrical. Mastering the use of wiring diagrams enables a technician to better troubleshoot the system electrically, which will facilitate troubleshooting the entire system with more accuracy and precision.
In the example shown, line 5 has the numbers 5 and 11 printed to the right of the line. This means that the load (HR) controls a set of contacts in lines 5 and 11. The contact in line 5 is normally open and the contact in line 11 is normally closed. Many times there are also small numbers printed next to each of the electrical components on the diagram. In our example, we have colored these numbers blue. These smaller numbers represent the manufacturer’s numbers stamped on the actual electrical component. For example, the compressor overload OL2 has the numbers 3 and 4 printed next to it. This means that the wiring shown on the diagram will be physically connected to terminals 3 and 4 on the actual overload. This allows a technician to more easily locate an exact point in the wiring of the system. Lastly, some diagrams will also have a circled number shown next to a line on the diagram. These circled numbers are used to identify the actual wires used on the system.
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).
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