furnace will not shut off

[Drew McGee]

I ran into an electric furnace today that will not shut off. It is central forced air, and it would not shut off if the temperature was met, so I switched the system off, and it wouldnt stop blowing hot. Finally had to shut it down at the panel, but was wondering if anyone had an idea as to the cause.

Thanks for any help,

Drew McGee

[Paul Kondzich]

Its been awhile, but possibly the sequenser (which sequenses the heat strips) or a contactor??

[Scott Patterson]

I ran into an electric furnace today that will not shut off. It is central forced air, and it would not shut off if the temperature was met, so I switched the system off, and it wouldnt stop blowing hot. Finally had to shut it down at the panel, but was wondering if anyone had an idea as to the cause.

Thanks for any help,

Drew McGee

I would be betting on a bad thermostat.
Was the system running before you broke it? :D
I hope you told the homeowner that you shut down the system.....

[Billy Stephens]

I ran into an electric furnace today that will not shut off. It is central forced air, and it would not shut off if the temperature was met, so I switched the system off, and it wouldnt stop blowing hot. Finally had to shut it down at the panel, but was wondering if anyone had an idea as to the cause.

Thanks for any help,

Drew McGee

Drew,

How long did the blower run after the temp was met / switched off ?

[Drew McGee]

The system was on, but I lowered the temp. I prefer the term 'failed under test', but the seller is aware of the situation.

The system ran for around 30 minutes, but it was more than the blower, the strips were hot the entire time, even after it was off at the thermostat.

[Jim Luttrall]

Sequencer failure, very common failure on electric furnaces.
A thermostat failure is not likely if you used the system switch (Heat, Off, Cool) after turning the temperature back to normal.

[Drew McGee]

Thanks for all your answers

[Gunnar Alquist]

I would be betting on a bad thermostat.
Was the system running before you broke it? :D

Scott, you crack me up.

[Jim Zborowski]

Is the fan switch set to "run" or "AUTO'?

[Jerry Peck]

Is the fan switch set to "run" or "AUTO'?

Jim,

That was my thought too, and (I suspect) that of Billy when Billy asked "How long did the blower run after the temp was met / switched off ?".

Drew said "The system ran for around 30 minutes, but it was more than the blower, the strips were hot the entire time, even after it was off at the thermostat."

That would not be the fan set to 'On' instead of 'Auto'.

[Jerry Peck]

I ran into an electric furnace today

Like Scott said, you broke it man. :)

You really need to stop running into things like that. :D

[Billy Stephens]

Jim,

That was my thought too, and (I suspect) that of Billy when Billy asked "How long did the blower run after the temp was met / switched off ?".

Drew said "The system ran for around 30 minutes, but it was more than the blower, the strips were hot the entire time, even after it was off at the thermostat."
.


I was thinking cool down period, my money is on the Limit Switch. :)

[Jim Luttrall]

The limit switch is a safety that never comes into play unless the furnace is on a runaway. The blower and heat strips continuing to run could be stopped by the limit switch if there was too much heat, but that would only occur if the normal operating control is broken.
Sequencer switch is the culprit.

[Jim Zborowski]

OK, I missed that. Thought he said the blower wouldn't stop.

[Billy Stephens]

The limit switch is a safety that never comes into play unless the furnace is on a runaway.
.
Sequencer switch is the culprit.

Either way time for The Trades. :)

[Jim Luttrall]

Either way time for The Trades. :)
Agreed.

[Drew McGee]

Thanks again. By The Trades, are you saying its time to call in a service tch?

[Jim Luttrall]

Yes, "Trades" would mean someone specifically trained in one of the specialties such as A/C, Electric, Plumbing.

[Drew McGee]

Thanks. That was my initial call,I was just trying to get a handle on the cause.

[TOM DEEHAN]

I was thinking cool down period, my money is on the Limit Switch. :)

If the limit had tripped (over heat condition) and the heat strips were still running, that sounds like a melt down. Better call the HVAC guy.

[TOM DEEHAN]

[quote=Drew McGee;31082]I ran into an electric furnace today that will not shut off. ]

Did you have the right thermostat? :D