Forced Air Hot Air Heat Question

[Ed Hayes]

All my life I have lived in home heated with oil and hot water radiator heat. We recently moved and live in a house that has oil heat and forced hot air. My question is when heat is called for the air is blown out of the vents for very short periods of time, maybe 15-20 seconds) It then shuts off and maybe 20 seconds later it starts again. It repeats this on-off cycle until heat is no longer called for. The time the blower stays on seem to increase slihtly as the number of on-off cycles increase. My question -- Is this normal??? My thermostat has the capability of forcing the blower to stay on for an extra 90 seconds after call for heat ends. Should I use this setting or is what is happening now normal?

Thanks

[Patrick Cleburne]

No, that's not normal-- the heat cycle should be much longer. It sounds like it needs an adjustment.

And I would let the fan run after the burner stops. There's still heat in the system and you might as well have it blow into the house instead of dissipate up the chimney.

[trader4]

There are two switch settings on the furnace hot air plenum that control this. One sets the temp when the blower turns on, the other sets the temp when the blower turns off. The turn on is set higher than the turn off. That way, the first air to come out is nice and warm. The turn off is lower, so that after the burner shuts off, it keeps air moving to get just about all the heat out of the furnace.

Sounds like yous are set incorrectly. My furnace will do the on/off action your describing if the house is very cold, like 40 degrees and the furnace is turned on. It occurs then because the air is so cold, that after the blower starts, the cold incoming air drops the air temp in the hot air penum below the shut off temp. After awhile, as the temp rises, it starts behaving normally. Under normal conditions, the burner should come on, then a couple mins later the blower, then after

15 mins or so the burner shuts off, then a few mins later the blower shuts off, completing the cycle.

[m Ransley]

Short cycling is hard on the furnace components . Your efficency is also suffering greatly. If you have not had a pro go over it now is a good time.

[Greg O]

No it is not normal. The fan control on the furnace MAY need adjustment. It could also be other issues with the furnace itself causing the fan to cycle. The fan control senses heat from the heat exchanger and runs as needed. Yours may need replacement, or adjustment, or some other problem. Get the furnace looked over by a GOOD oil man. Oil furnaces are typically ignored until something stops them from running. Most people do not realize that oil burners take more service than gas systems to keep running properly. Your furnace may need just a simple adjustment, or perhaps a through cleaning. Greg

[mm]

I wouldn't fiddle with this adjustment until the other stuff is working. I think this is only to keep the fan on *after* the burner stops, and you don't say but I think your burner is also stopping, not just the fan.

After the other stufff is working, it will probably not be necessariy to change this.

If the previous owner knew he was moving and the furnace was giving small problems, he might not have called anyone. But You should have a service call anyhow to tell you what all you need to know. Tell him about this problem of course.

He'll want to sell you a contract. I really don't know if those are a good deal. One oil company impolied they wouldn't put me on autmatic delivery unless I got the maintenance contract, but they did. After all, if they don't come automatically, a customerI might call someone else.

Remove NOPSAM to email me. Please let me know if you have posted also.

[TURTLE]

this is Turtle.

this short cycling is no where near right and you need to have a good oil furnace man look at it. i can think of 8 reason that could be wrong with it and maybe more if i really think about it. Also It is costing you money by heating with it short cycling condition.

TURTLE