Fan limit switch

Heating · Electric Furnaces · printed page 202 (PDF page 203)

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Book index entries

Electric Furnace – Fan Limit Switch for Electric Furnace Electric Heating Systems

Text in the illustration

hot air plenum
25 kw electric furnace
electrical supply
blower
cold air return
temperature probe
cover
manual fan switch
fan ON - typically 125°F
high limit - typically 200°F
100
150
200
250
300
350
the fan may be set to come on at the same time as the elements or may have a slight delay (e.g. when plenum temperature reaches 125°F) so that cold air isn't blown through the ducts initially
the fan turns off when the elements turn off

Generated explanation

The illustration shows a cutaway electric furnace with a blower in the lower compartment, electric heating elements above, and a hot air plenum at the top. An enlarged fan limit switch shows its temperature probe, adjustable dial, manual fan switch, and removable cover. A dial detail identifies a typical fan-on setting of 125°F and a typical high-limit setting of 200°F. The annotations explain that the fan may start with the heating elements or after a slight delay to avoid initially blowing cold air through the ducts, and that it turns off when the elements turn off.

Components

electric furnace electric heating elements blower hot air plenum cold air return fan limit switch temperature probe manual fan switch temperature setting dial switch cover electrical supply conduit electrical wiring

Materials

sheet metal metal conduit electrical wire