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Basic Electrical Theory May 31, 2022, 12:11 am
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What does "RES" mean on a contactor or relay?
Look closely at a contactor on your truck, and you may find some interesting ratings you never noticed—things like terminal ambient temperature ratings and torque specs. One reading you may overlook is the RES AMPACITY of the contactor or relay. The RES rating is the RESISTIVE LOAD AMPACITY (amperage capacity) or rating. Remember, a contactor and […]Read more
Multi Tap Primary Transformers
Have you ever seen a low-voltage transformer like the one shown above? It has multiple input (primary) taps for a good reason. It is common to find three-phase and single-phase equipment rated to operate on both 240v and 208v power. That is because three-phase power can either be 208v leg to leg when the building […]Read more
Open and Closed Case
I know I'm gonna get some eye-rolling here, but it needs to be said. When we teach electricity to new techs, we use a lot of “water” metaphors. We talk about volts like PSI, amps like flow, and watts like GPM (speaking of GPM in HVAC, check out our article on hydronics HERE). Even the […]Read more