On 6/23/2012 10:47 PM, Winston wrote:
On Sat, 23 Jun 2012 22:29:18 -0700, mike wrote:

On 6/23/2012 9:21 PM, Winston wrote:

(...)

--Winston-- Now looking for an accurate NG totalizing flow meter.

I have one of those on the outside of the house where the gas comes in.
The test dial is pretty high resolution. I used that to determine the
gas input of my furnace.
Then I put a flapper on a microswitch that sits on a register. I know
how long the fan runs and how much gas is used for that time. You have
to factor out the preheat and cooldown time differences between the fan
and the burner.
I stuff that into a PalmIII and log/plot the on/off times for each cycle
and a running average.

Interesting approach. Somehow I'd not considered that my water heater
and space heater run at a fixed consumption rate when they are on.
Yes, once you confirm what that fixed rate is, what it says on the tag
ain't always what you get, you still have to determine
when they're on.
I elected not to try to put wires into the furnace controller.
Sensing the fan let me put the sensor right were my electronics sat.
Thanks!

(...)

To do this with a gas water heater, you'd need to construct some sort of
flame sensor. You could tap off some signal inside the heater, but I
don't like messing with stuff that can blow up the house if I screw it
up. Insurance companies take a dim view of that.

Yup. I'm currently lusting after one of them ultrasonic
'clamp on' flowmeters instead. Nifty.

--Winston