On Wed, 15 Dec 2010 18:17:20 -0500, wrote:

OK - I've got some numbers.

I dug out the handy Amprobe and checked the current draw on my
Tempstar ntv6050fb furnace.

On low speed circulate it is drawing .21 amps at 116 volts AC.
When it calls for heat and the Eductor fan is on high, and the hot
plate ignitor is on, it draws just over 2.2 amps. When the gas lights
and the ignitor shuts down, it draws 2.0 amps, and with the furnace
running normally, the unit draws all of 1.5 amps. Thats about 175 VA.

Yesterday the furnace ran 6 hours and 17 minutes, and so far today 4
hour and 12 minutes. Yesterday was a pretty cold and windy day.
If it runs 6.25 hours a day at 175.3 va, that is just a hair ovr 1kWh
per day, and the low speed blower, running the other 17.75 hours at 34
va, consumes another .6 kWh.

IF the furnace cycles 20 times (I have not counted, but I figured I'd
guess on the high side) the eductor and ignitor, running aprox 1.5
minute for each cycle, draw another .7 amps,for another 0.3 ah or .035
kWh per day - for a total of something just over 1.6 kWh per
day.(48kWh per month)
At 7.5 cents per kWh for the first 1000 per month, and 8.5 cents per
kWh from there up, over and above the roughly $16 per month
"distribution fee" from Waterloo North Hydro, if I didn't use
electricity for anything else to spread the distribution fee over, it
would cost me about $20 a month to run the furnace.
Since I DO use electricity for other things, the incremental cost to
run the furnace is only something like $4 per month for the
electricity.

A half HP PSC motor, running only with the furnace calling for heat,at
475 va, would consume 93 kWh of power, costing $6.98 a month, just
for the blower.
If the blower on low speed circulate keeps the temperature more even
and the furnace does not need to run as much because of that, the cost
for the single speed PSC motor would be higher - possibly approaching
$10 per month.

On the other hand, if, as some have theorized, circulating the air
looses heat to the outside and/or basement, NOT running the low speed
circulating fan would cause the furnace to run less - saving not only
the .6kWh, but also some furnace run time.

Anyone with a PSC blower motor on a conventional standing pilot light
furnace have an Amprobe and want to check the blower current draw for
a sanity check?

I'm just guessing 475 Va running current.

The low speed blower is set at 600 cfm with a .1" static (default)
and the heat blower speed is also at default, 0.20" static, with the
AC set to 900 cfm at 0.50" static, default for a 2 ton AC according to
the installers notes. The default for heat was set by the specified
heat rise across the heat exchanger