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hvacron
03-14-2017, 07:45 AM
Why would an electric duct heater need a 24v relay on incoming control voltage? Had 23v to relay but didn't energize contractor.


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CHAINIK
03-20-2017, 06:01 PM
Don't know for sure without a model number, but that's a common way to ensure that the heater doesn't come on without the fan signal.

There's two common ways, an actual airflow switch in the heater, which won't turn on the heat unless air is actually moving through, and then the kind where the heating call is routed through a relay that's controlled by the fan signal. That sounds like what you got. The drawback to this approach is that it only keeps the heat from coming on without a call for fan, doesn't help with something like a broken belt or severely clogged filters.

hvacron
05-06-2017, 08:58 AM
Don't know for sure without a model number, but that's a common way to ensure that the heater doesn't come on without the fan signal.

There's two common ways, an actual airflow switch in the heater, which won't turn on the heat unless air is actually moving through, and then the kind where the heating call is routed through a relay that's controlled by the fan signal. That sounds like what you got. The drawback to this approach is that it only keeps the heat from coming on without a call for fan, doesn't help with something like a broken belt or severely clogged filters.

It was controlled by a fan signal. Which wasnt allowing it to turn on. Had 2-a44 belts that were on there way out. Also was connected to Honeywell control system that maintenance guy played around with and turned signal off to that heater. Not allowing heater to turn on


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