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reznor unit heater problem

Marv's picture

OK heating guys. In my workshop I have a Reznor unit heater, about 10 years old. Last spring, I shut it down because it wasn't cycling correctly. I tried to start it up today and figured out that the power vent won't shut off. The heater cycles OK but when the heat cycles off, the vent wont shut down. I have to turn the power off to the unit to stop it. What should I be checking?

You get out of life what you put into it......minus taxes.


Marv

You get out of life what you put into it......minus taxes.

Marv

(post #112414, reply #1 of 5)

Hi Marv, I'm not a heating guy,ust an electrician, and I wonder if your unit has a HIGH limit for the vent fan and possibly that switch has" failed closed" ?

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(post #112414, reply #2 of 5)

Not sure but I've got an expert coming to look at it tomorrow.

You get out of life what you put into it......minus taxes.


Marv

You get out of life what you put into it......minus taxes.

Marv

(post #112414, reply #3 of 5)

if you have the time, let us know what it was.... OK?

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(post #112414, reply #4 of 5)

What's the serial number? I'll take a look at the wiring diagram.


What you should be checking is the control wiring that fires the burner. There is a specific logic that must be satisfied before it fires. Call for heat, vent motor starts (verified by an air proving switch/lockout relay), gas pressure is present, gas valve opens and ignition is instigated (unless a standing pilot is invloved, the TC shows pilot lit before gas valve opens). When the unit shuts down all of the startup/run relays should drop out any contacts made. Sounds like you have an old relay and the contacts are sticking.


Edited 10/12/2005 10:57 am by Tim

(post #112414, reply #5 of 5)

The heater will cycle properly but after the burners shut down, the vent motor keeps running.  I'm thinking a relay in the vent motor is stuck.

You get out of life what you put into it......minus taxes.


Marv

You get out of life what you put into it......minus taxes.

Marv