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Electric furnaces

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Published
July 10, 2009
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I have an electric furnace. What sounds does the furnace normally made?

Inits simplest form, an electric furnace contains electric strip heatersand a blower. The electric strip heaters are similar to the red heatingstrips you'll find inside your toaster, or within an electric spaceheater. When energized, these heaters make no noise at all, so you willnot be able to tell if they are energized by listening to them. Youwill hear the blower operating, though.
Forthe electric heaters to be energized, the blower must be operating.There must be air moving across the heating elements for them to comeon. A sail switch mounted within the duct system accomplishes this.When air is moving inside the duct, the sail switch moves and energizesthe heater circuit. So, at the beginning of the heating cycle, you mayhear the clicking of some electrical switches as the heaters energize.Otherwise, with the exception of moving air, electric furnaces arenearly silent.

I have an electric furnace. What might indicate that there is a problem with my system?

Theone thing about electric heating systems is that they usually eitherwork or they don’t work. It's rare that an electric heating systemprovides some heat, but not enough heat. Here are somethings to lookout for:
  • Noticeable reduction in airflow coming from the supplygrills. If you notice this, check, clean, or replace your air filtersfirst. If the filter is clean, there may be a problem with the blowermotor or the blower itself. If there is an electrical problem with themotor, it may not be turning at the correct speed, resulting in theairflow reduction. This will eventually lead to the overheating of thestrip heaters, and the opening of the internal safety switches intendedto protect the system. Other causes for this situation include a dirtyblower wheel, internal duct blockages and closed or blocked supplygrills.

  • No air moving at all and no heat. If thishappens, there is likely a problem with the blower motor, not theelectric strip heaters. Remember, the electric strip heaters can onlyenergize when there is airflow in the duct system. If there is noairflow, there can be no heat. There might also be an electricalproblem with the system. Check the main fuses and circuit breakers tosee if there is power going to the system. If the main fuse is blown orthe circuit breaker is tripped, determine the cause for failure beforereplacing the fuse or resetting the breaker.

  • Cold air isblowing from the supply grilles. This may or may not be normal.If thefan is in the on position, the blower will be moving air through theduct system constantly, not just when the heaters are energized. If thefan is not in the on position, and the thermostat is calling for heat,there may be a problem with the sail switch or the electric heatercontrol circuits, safeties, and sequencers. To avoid an unnecessarycharge, check to see if the thermostat is calling for heat beforecalling for service.