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On a Nortron Model 21B15 electric furnace; The blower fan not working, I changed the lower left fan relay after noticing a burnt spot on top of the unit. The furnace worked for a week or two, then an intermittent problem occured with the fan and heating. I then changed both fan relays, and the intermittent problem reappeared. At one point I noticed a humming sound on the left relay while the fan would'nt go on even if the element(s)were producing heat. I'm at the point of changing the heat sequencer switches, but I chcecked the transformer outpu (Broan 24V 35va; model LR23056/ part 30300008) and I'm getting 28.5V ouput. The fan relays and sequencers are identified 24V, Is the +4.5V difference on the output NORMAL? Or is it too much voltage; enough to overheat the relays and sequencers?
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the output of the transformer drops a little when a load [a relay] is put on it. I would check the sequencer coil as being open. -
Usually a 24volt transformer starts out about 27+ volts. I don't know how accurate your tester is. When the 24volt power starts powering controls you will start getting a voltage drop. Relays can chatter if the power drops lower than 24 volts, but its okay to have a little more voltage, like 26 volts. PaulOriginally posted by Mic View PostComment
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Thanks, as you indicated, at start, I get a drop to 27.7V : Transformer is OK. So I will proceed changing the double sequencers, as was done by 'JCforever' in November 2009. He was experiencing the same symptoms and that was his solution. I posted a message to his intent asking if the intermittent fan and heat failure had dissapeared for good. No answer yet.Comment
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the sequencer relay has an extra set of contacts for a fan or auxillary equipment. each progressive sequencer has these contacts to keep the fan or relay energized as the heat requirement increases or decreases. when the "stat" is satisfied, the last sequencer drops off and shuts down the fan.Comment
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