Hot air system cycle problem

Joe B

Gas fired fired hot air system. Gte ignition upon increse temp request. Burner turns on urns for a while, ciculator tuns on and burns turn off immediately. The cycle continues the burner does not stay on when ciculator fan is running.
Extensive amount of time to heat home. Please advise what are the most likely problems example ( thermostat, internal control printed circuit board). How do I test for it.

clammy

sounds like it may be one of two things the easier of which is a dirty filter or not enough return air which makes the burner cycle on and off.the burner comes on run a few and cycles off the fan contiues to run then cycles off a quick way to check is to remove the blower door and run the unit if the burner does't cyle off then that's your promblem.do not operate the unit with the door off you can pull flue gases into your living.other things to check is dampers inthe main or branch ducts which could be closed,check the blower speed it may have to be lowered and use a ductalator to see if your ducts can handle the furnaces c.f.m. rating also last of which the furnace could be oversized which would give you the same systoms.p.s. howes the draft on your chimmey good luck and i hope this helps you out

Unknown

Forced Warm Air

systems using a time on time off fan control will do this. If it is a temperature on temperature off fan control that is different. As posted by someone else check the air flow on the unit, make sure filter is clean. Is this a spark ignition system? It is possible that when the blower comes on the flame is being pulled away from the sensor. Possibly a cracked heat exchanger or loose blower door. Suggest you hook up a microamp meter to check pilot. It would also be a good idea to do a room pressurization test and combustion analysis.

Give us some more information and control numbers.

Dan Law

Cycle problem

Along with the other posts, I'd suggest the following: Check the thermostat heat
anticipator setting. An anticipator is a small heater within the thermostat that essentially
"fakes" the thermostat into terminating the call for heat before the room actually
reaches setpoint. The residual heat "blown" from the furnace after the burners
extinguish, carries the room to setpoint. This anticipator is set to match the
current draw on the heating control circuit, during the call for heat cycle. IE
current draw is .75 amps, the anticipator is set @ .75. If set too low, you can get the cycle you describe.

The adjustment is usually a
small arrow shaped arm sliding on a wound resistance heater under the
thermostat cover. The instrument used is a single purpose anticipator
ampmeter, or a conventional clamp-on ampmeter. The conventional often
requires you wrap 10 turns of a jumper around the meter jaws to act as an
amperage multiplier. (10 turns causes the .75 amps to read as 7.5 amp,
something you can read on the instrument.

Something we see a lot of is a failure
to properly adjust the old thermostat after a furnace replacement. A new furnace
will have a very different control circuit amp draw than an older unit. Often a quick
read is taken which indicates only the pilot circuit energized. You have to wait for
the pilot to prove, then read main valve amperage added to the total.

If your
uncomfortable or unfamilliar doing this, time to call a pro who would check out all possibilities and
act accordingly.