Category: Controls

Averaging Thermistors

From time to time someone asks about thermistor sensor averaging. Typical questions are: Why do I have to use four? Why do they have to be connected in series-parallel? What the heck is series parallel? Have you ever seen a

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Control Board Troubleshooting- The Ins ‘n’ Outs

Electronics work just like you do; they determine what’s happening by looking at inputs like temperature and pressure, and decide what to do based on what they “see”. The only difference between your brain and electronics is you use your

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Control Board Fails

Control Boards rarely fail, they’re usually misdiagnosed or murdered. When control boards do fail it’s normally an output contact failure caused by age or an electrical surge like lightning or a technician shuffling across carpet before touching it. It’s a

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The In (puts) and Out (puts) of Control Boards

A Control board looks at inputs and generates outputs based on the inputs it sees. That’s it. Let’s put this in perspective- Input= you hit your thumb with a hammer. Output= you swear. If the input doesn’t happen (hammer hitting

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Control transformers: Watt’s a VA?

It’s 4:50pm. The unit you’re working on has a blown control fuse. The supply houses close in 10 minutes, and it’s 20 minutes away. You scour every shelf, box, and bin in your truck looking for the ever elusive 3amp

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Digital Thermostats 101

Customer: “My ski jacket zipper thermometer says 70 degrees, the new thermostat you installed says 71 degrees…something’s wrong with it” Contractor: Why me? While the infamous $10 ski jacket thermometer is about as accurate as divining rod, you may be

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Reverse Polarity Faults

Is that new furnace you installed shutting down on reversed polarity? Did you check, double check, and recheck the ‘hot’ and ‘neutral’ lines but still can’t solve the mystery? Here’s a tip: Take a look at what other appliances are

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Thermistors 101

When electronics found their way into the HVAC field they brought thermistors along for the ride. Now they’re lurking everywhere from simple residential thermostats to centrifugal chillers. What are they? What do they do? What’s NTC and PTC mean? What

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Zone Systems 101

When zone damper systems are applied, installed and used correctly, they’re amazing. Now, if only they were always applied, installed, and used correctly….

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Got 24 Volts?

Got 24 Volts? Just about every HVAC system out there has a low voltage control circuit, and just about every one of them is 24 volts A/C. You name it, it probably uses it: gas furnace, oil furnace, condenser, heat

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