Bert Addresses Some Concerning Calls
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For example, some techs who are already experienced enough to have their own van have been calling about voltage drop, but they were measuring voltage to ground instead of to the other leg of power. That indicates that they avoided that issue instead of addressing it and asking how to measure voltage properly.
When technicians have a few gaps in their knowledge, those gaps may seem easy enough to avoid on most service calls at first. But when the gaps start increasing in number, it gets a lot harder to avoid those areas of poor understanding.
Bert tries to tackle a common knowledge gap by teaching the techs about proper meter use. Voltage measures the potential difference between two objects. When you put the meter leads at two different points on the same wire, the meter will read zero volts because there is no difference between the leads. However, that doesn’t mean that the wire isn’t powered! Before you check anything electrical, it would be wise to do a safety check to ground; that won’t let you know if the equipment is working, but it will let you know that you have electricity.
Many meter issues can be cleared up if you simply know where your power is coming from. You want to make sure that you have 240v (or 208v, depending on the application) making it to the motor. You can also check the relay and the contactor to make sure the electricity is going to the proper locations for running a condenser fan. Some systems, such as Lennox units, require the electricity to take different paths than expected; be mindful of that when you work on A/C units. Find out where the equipment wiring connects and check the voltage of that.
Bert also covers pressure switches, which have been responsible for a few of those concerning calls lately. A spring forces two plates of metal together on a high-pressure switch, and that allows a path to form from one end of the pressure switch wiring to the other. When the pressure gets too high, the spring forces the electrical path open. The high-pressure switch is a normally closed switch.
The refrigerant pressure must be high enough for the spring to connect the plates on a low-pressure switch. When the pressure is too low, the path remains open, so the low-pressure switch is a normally open switch.
Even the most knowledgeable techs have gaps in their knowledge and need to contact tech support or do more research to solve a problem. There is no shame in not knowing something, but you would be better off addressing your lack of knowledge and learning something new instead of avoiding those problem areas and pressing on with your job.