Intermintent operation

[David C. Macy]

What would be the cause of a 7 year old Armstrong mid efficiency furnace with monoport burners & electronic igniter to have intermintent operation?

The furnace would operate, ignite and then after about 2-5 seconds the gas would go off at the burners and then the furnace would try to ignite again?

Thanks

[Jeff S. Vogan]

David,
I have seen this once before. After the electronic ignition lights the burner, there is a sensor at the end of the burner that tells the unit that the burner got lit. If that sensor gets "dirty" or is faulty, and does not detect the flame when it is lit, it thinks the burner did not ignite, and is just pumping out gas. As a safety precaution, it will shut the gas to the burner off thinking it isn't lit. Then, it will attempt to re-light it. This cycle will continue over and over and over........

[David C. Macy]

Originally Posted by jvogan

David,
I have seen this once before. After the electronic ignition lights the burner, there is a sensor at the end of the burner that tells the unit that the burner got lit. If that sensor gets "dirty" or is faulty, and does not detect the flame when it is lit, it thinks the burner did not ignite, and is just pumping out gas. As a safety precaution, it will shut the gas to the burner off thinking it isn't lit. Then, it will attempt to re-light it. This cycle will continue over and over and over........

So it just needs a new ignitor? Thanks. I have seen this before and now with your help I can better explain if I happen to have this scenerio again.

[Jeff S. Vogan]

Not a new ignitor, the ignitor is lighting the burner. It needs a new flame sensor...a very minor repair by an HVAC guy. Literally takes about 5 minutes to replace...minor costs! Good catch, BTW!

[David C. Macy]

Originally Posted by jvogan

Not a new ignitor, the ignitor is lighting the burner. It needs a new flame sensor...a very minor repair by an HVAC guy. Literally takes about 5 minutes to replace...minor costs! Good catch, BTW!

Thank you very much.

The weather here is brutal. More snow & cold then in the winter. I told my six year old that santa claus is dropping off the eggs and the easter bunny is staying in the ground until it warms up.

[Chad J. Willick]

i believe Jeff is correct. i have seen the same thing where the senors eye was covered, in this case not dirt but with a film from burning to rich. how did the flame look?