Heat Overload turns on Furnace Blower

[maradcliff]

We have been having a heat wave, with temps up near 100 degrees for well over a week. Today it got so hot in my house that the furnace blower kicked on. I thought that was rather odd, since I do not have central AC. Then it hit me. It was so friggin hot that the furnace sensor (probably a klixon) thought the burner was on, and the blower kicked in. I shut off the power to the furnace, but that tells me it's time to set up my tent, since it's just too frikkin hot to stay in the house, especially since Sunday is supposed to hit some sort of heat record.

Mark

[Anonymous]

Good to hear it's happened to you too. I've been watching a friends house while he's away.

The thermostat has setttings, and it was set to

THe inside of the house was close to 100 degrees, and the furnace blower motor was running.

The only way I could get it to stop was to flip the circuit breaker !

I was getting ready to call a HVAC guy until I read your post.

[Harry K]

Why shut it off? It is a great aid to cooling the house even without A/C. Mine goes to ON as soon as the house begins to warm up (about noon) and stays on until bedtime (midnight). A/C kicks on much later that way. The fan itself is only a fractional horse motor so the cost is minimal, much less than running the A/C.

Harry K

[webmaster]

If its an older model, with a bi-metal adjustable fan limit switch, its either set too low, or out of calibration.. the overload is normally set at 250F..so..guess what?

[lp13-30]

If that furnace is in the attic it is possible for the temperature to get high enough occasionally for a bi-metal fan switch to to close even if it is properly adjusted. I have also seen it happen on mobile homes with the fixed disc fan switches. Solution-- run the A/C. Larry

[HeatMan]

Klingons? Aren't those the things that hang on before you wipe your bottom?

And you wonder why most people think you're a hack....

[Harry K]

Right. It is a great way to help keep the house cool. The fan is on a fractional horse motor, costs pennies to run and will keep the A/C from kicking on for another hour or two.

I posted that this morning (and two others) but haven't seen any of them.

Harry K

[Stormin Mormon]

I had that happen in my last trailer. Had those narrow slat windows, and I didn't have an AC.

Yep, those Klingons do get hot.

[Stormin Mormon]

Just leave it on. Won't hurt anything.

[RP]

My version of physics seems to conflict with that notion.

hvacrmedic

[Harry K]

Try it and see. It works by having the air in the room moving. You feel more comfortable at the same temperature and can set the A/C higher. Mine goes on about noon every day in summer and stays on until bedtime. If you have a basement and have a way of sucking your feed air from there, you gain even more.

Harry K

[Mark]

Well its not just the overheat setting

My furnace blower continues to run after the fire shuts off as the heat exchanger cools down and it continues to run untill the air is at about

100 F. Due to hystereisis it takes a higher temp to get it to turn on, but onece on, it won't turn off untill the air drops below 100F.

His blower control may be a bit out of adjustment but not anything serious.

Mark

[webmaster]

And its against all known building codes for a reason.

[webmaster]

No one said it was.

Belive thats what we said..

[RP]

So it's the higher setpoint that keeps it from kicking on rather than the moving air? :) hvacrmedic

You

[TURTLE]

" [e-mail]" wrote in message news:qjuCe.79$ [e-mail]...

This is Turtle.

WOW Your fixing to tell me something here why drawing air from a basement is against every building code there is. what if the draw air supply / furnacers are in the basement ?

TURTLE

[Stretch]

Harry,

He can't set his AC temperature setting higher. He doesn't have AC and it is over 100 degrees in his house. I recommend he buys a window unit while some are still available and put it in his bedroom and spend all his time in the house there. And leave the power off to his furnace.

100 degree wind will not feel cool.

Stretch

[Stretch]

Steve, I habe a copy of the international building code and the International residential mechanical code. I could not find where it said you cannot have a return in the basement, unless the basement was so small that it would remove the combustion air from the room and backdraft the flue. Perhaps you could quote chapter and verse?

However, it still would not cool the house in that situation, unless you have a VERY COLD basement.

Stretch

[webmaster]

Do you have a copy of the IBC? If you do, read it retard. You cant just arbitraly start drawing air from a basement.

>

[Harry K]

How so? My basement is cool enough that there is a noticeable drop in temp as I go down there. The air is very definitely much cooler than the living area and for sure cooler than the A/C cut-in temp. It is not VERY COLD tho. Any air cooler than the cut-in temp is an aid. Granted that air doesn't last all that long.

Harry K