Tip & How-To about Ruud Rheem Enclosed Fan Relay 42-25104-06 Za2900-1c-24a
A fan relay has 2 switches, a NC, normally closed switch
and a NO, normally open switch.
The relay has a coil that acts as an electromagnet and when energized with 24 volts from the thermostat will close the NO and open the NC switches.
The NO switch is the High speed , the NC switch goes to Low speed however as it is NC a temperature or time delay is what actually controls the low speed, low speed is the heat speed.
The NO switch in the fan relay goes directly to the High speed lead, this is the Cooling speed and the Fan On speed.
The 24 volt coil in the fan relay is wired to Green from the thermostat and Common 24 volt neutral leg.
Posted by KD Grayson... on
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