Furnace Problem

Question

Suburban NT-30SP.  Still trying to diagnose my intermittent furnace problem.  Want to make sure my thermostat is ok.  I get instant fan when I turn the thermostat up.  Is this normal?  This model furnace does not have a time delay relay on it.  Should there be one in the thermostat?

darsben1 · Answer

You should get instant fan. Then the furnace does all its prechecks. Instant fan gives time for the fan to purge the firebox of any  gas should you have a leaky valve etc. Also the sail switch has time to close the connection to allow the gas valve to open.

harry_and_thea · Answer

Thanks.  So problem is not thermostat.

2oldman · Answer

I get instant fan no matter where the temp setting is.

pauljdav · Answer

All the thermostat does is provide instant power to the furnace main board. The main board desides what to do next.

I have had to replace the main board with a fans 50 plus on every furnace I have had. I recommend it as it is much better quality than the original.

darsben1 · Answer

My first check would be the sail switch

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