Short cycling of furnace

[lagudo]

Hi Guys,

I have a question on the cycling of my NG furnace. When called upon for heat it fires up but only stays on for 3 to4 Minutes then shuts off and stays off for about 5 to 7 minutes. It's not even close to reaching the temp. that has been called for. Needless to say, this never brings the temp. high enough to make a difference. I thought that maybe it's a faulty thermostat but I have never had any problem with cooling and short cycling. I have called to get my unit serviced but I am looking for information I why is this so and what component could be causing this problem.

Thanks in advance.

[Charley L. Bottger]

When called upon for heat it fires up but only stays on for 3 to4 Minutes then shuts off and stays off for about 5 to 7 minutes.

Will be one of the safety switches Hi limit going bad, combustion air pressure switch restricted are the two most common. Do you have a control board with blinking led lights if so read your diagram the blinking lights will correspond to the problem.

[Michael Larson]

Louis,

In addtion to what Charley said, tell us more and post a picture of the unit with the service doors off. There are some very qualified people here willing to help another HI.

[Roy D. Cooke, Sr]

Is the Filter dirty ......... Cookie

[Brian A. MacNeish]

Originally Posted by rcooke

Is the Filter dirty ......... Cookie

Or the fan not operating. This would cause the "hi-limit" (temperature) switch to shut the burner down until the temperature over the heat exchanger dropped below the preset hi-limit temp of usually around of 200 deg F. Then with the thermostat still calling for heat, the burner would come back on to repeat the sequence.

[ldapkus]

http://www.nachi.org/forum/showthrea...+cycle+furnace

[rwand1]

Is this a high eff. or mid eff. furnace?

Have the homeowners closed the supply ducting down or closed off a number of floor vents?

[mdiplock]

Furnace short cycling.
No heat to home.
Possible hi temp/fan limit switch problem.
Recommend further evaluation by a qualified service technician.

[Jeffrey S. Campbell]

Originally Posted by mdiplock

Furnace short cycling.
No heat to home.
Possible hi temp/fan limit switch problem.
Recommend further evaluation by a qualified service technician.

i think this was his personal home furnace vs. a inspection...

[Bob Elliott]

Mark I would leave out the third line.

[Jae Williams]

...or the heat anticipator in the thermostat.

[twasion]

Circulation pump may be inop.

[Charley L. Bottger]

...

or the heat anticipator in the thermostat.

How would this cause the furnace to cycle the burner on and off.

It's not even close to reaching the temp. that has been called for.

If the thermostat is still calling when the burner goes off it can not be the Thermostat or the anticipator

Circulation pump may be inop.

Did not know a forced air furnace had a Circulation pump. What are we talking about do you mean the blower motor.