On Monday, January 11, 2016 at 2:26:37 AM UTC-6, Don Y wrote:
On 1/10/2016 11:47 PM, ir wrote:
"Open rollout switch circuit" error message in furnace.

A friend called me and said his gas furnace keeps shutting off. It's
fairly new and a high effencincy type, which vents out thru PVC. It
has a digital readout which says "Open rollout switch circuit". I
googled that, and found a simple drawing which shows it as a sort of
sensor, and found a picture of one. Not much more.

I emailed him the pictures and told him to shut off the power and set
his meter to OHMS and check that switch. He said there are two of them
and they are both turned to the ON or CLOSED position (Not open).

The outside temperature is well below zero, and he has kids, so I told
him he better just call a furnace repair company. If it was an older
furnace I could probably fix it, (assuming I could get parts), but I
dont know anything about these "computerized" furnaces.

He called a furnace company, the guy is swamped with calls, but said
he will come as soon as he can, but that could be several hours. The
guy told him to use space heaters till he gets there. Even if I
thought I could help, I doubt my truck will start in this cold, so it
dont make any sense to try, knowing nothing about these kind of
furnaces.

All I know is that it's a Lennox and it's giving that error code.

While I'm sure the furnace repair guy will get there before I even get
a reply on here, I thought I'd post this to see if any of you know
anything about it... I always like to learn new home repair stuff.

What's the purpose of these switches and what could be wrong?

The switches verify the presence of flame where it SHOULD be and the
absence of flame where it SHOULDN'T be!

You (he) could have a blocked heat exchanger which is preventing
the flames from flowing up through it and, instead, backing up
into the blower compartment (*outside* the heat exchanger).
Likewise, a blocked flue or something blocking the combustion
relief (not enough air to support combustion).

Or, low gas pressure causing the flames not to jet into the heat
exchanger fully (doubtful).

There are usually diagnostic LED's on the control board (*in* the furnace;
usually in the blower compartment, NOT the burner compartment) that
will give you some detail as to what is happening.

The switches can usually be reset, manually. But, this is A Bad Idea
and really should only be done by a qualified technician - just to
run the furnace long enough to understand why it/they are tripping.
They function similar to a fuse: they should NEVER trip -- doing so
means something is likely very wrong.

You (he) may be able to get the furnace to run by reseting them,
but run the risk of CO poisoning, fire, etc. as the reason for
their initial trip probably hasn;t been fixed!


I've seen the wiring to a rollout switch melt and short out on a furnace before and the flue temperature safety switch shutdown the furnace. The simplest safety sensors just break the 24 vac control circuit. I'm not familiar with the latest newfangled Apple/Android OS Bluetooth WiFi controlled HVAC systems. o_O

[8~{} Uncle Furnace Monster