On Sun, 24 Jun 2012 16:42:18 -0700, mike wrote:

On 6/24/2012 1:42 PM, Winston wrote:
On Sun, 24 Jun 2012 15:01:42 -0400, Jim Wilkins wrote:

wrote in message
...

(...)

Perhaps I'll put an IR photosensor aimed at the burner. Or a
thermocouple nearby. Haven't decided.

--Winston

I'd put a thermocouple in the flue and capture both timing and heat
loss.

Yup. That flue does get pretty hot.

Probably couldn't hurt to replace it with an insulated flue.

--Winston

To what end?
Unless it's in a space you air condition.

Sorta kinda. This is in the garage.

I installed a large fan in the roof to exhaust some of
the stratified air that collected during the summer months
and made the garage quite uncomfortably hot after we had
the roof replaced (even during fairly mild summer weather).

The fan has worked a miracle and the garage is once again useful
during the hottest days and feels pleasantly cool during mild days.

The exhaust flue is common between the water heater and
the space heater. As I mentioned the flue does get fairly hot.
That is a real waste during the summer especially if it means
that the lost heat is causing less - than - ideal combustion gas
evacuation.

--Winston