On Mon, 06 Dec 2010 10:30:00 -0500, Home Guy wrote:
Steve wrote:
snip
How exactly do you improperly install a furnace?
snip
90% of those (ECM motor) failures were due to incorrectly designed
and sized ductwork that caused extreme static pressures.
Would these be the same ductwork designed and installed by licensed
contractors?
Would these be the same ductwork that was original to the homes in
question - the same ductwork that somehow didn't manage to dammage or
burn out the motor in the previous furnace - presumably an AC motor?
It is quite possible. A belt drive blower could put up with an awfull
lot
I'm sorry, but if my 36 year-old AC motor didn't burn out because of the
size of my existing ductwork, then it's a crock of **** that the same
ductwork is the reason why a new ECM motor burns up.
Blame the ductwork. When you have to explain to the customer why his
new $4000 furnace is costing so much repair hassles, blame the ductwork.
Not necessarily - but if the installer does not do the temperature
rize test and properly set the motor speed, you could get a failure
due to improper installation.
Correct term for vsdc motors is ECM. ECM motors are a crock of
****. Best you'll save is 100 watts compared to 1/4 hp AC motor,
and less if you have 2-speed AC motor. Saving 100 watts at 10
cents/kwh is about $100 (that's 100 watts continuously for an
entire year). Now subtract the electricity used by the furnace
otherboard, and various other blowers and condensate pump. The
extra 100 watts used by AC motors are dumped into the house as
heat - which is what you need in the winter (and spring and fall
depending where you live) so it's not all wasted energy.
You underestimate the difference in efficiency between a standard
induction motor and an electronically commutated DC motor,
PARTICULARLY with multi-speed AC motors.
At lower speeds ECMs can save over 60% of the electricity used by PSC
motors.
For example, in low speed circulation a typical PSC furnace motor will
use 350 to 500 Watts while an ECM will use 75 - 125 W.
You need to read the entire study at:
http://www.nrc-cnrc.gc.ca/obj/irc/do.../nrcc38443.pdf,
but an interesting part is the following - with the same airflow,
"The power use of the ECM and the PSC motor were measured in one-time
tests using a Nanovip power meter. The ECM used 16.5 Watts in
circulation speed and 284 W in heating speed, while the PSC motor used
350 W in circulation and 490 W in heating. Thus, the ECM used 58% as
much as the PSC motor in heating speed, but only 5% as much in
circulation. The ECMs flow rate was almost identical to the PSCs in
heating speed, and was 47% of the PSCs in circulation speed."
you need to do some more homework here.
Ditto
You need to show you're a man by pointing out exactly which of my
statements above are wrong.
I'm right when I say that:
1) ECM motor uses 100 less watts when running full speed compared to 1/4
hp AC motor running at full speed.
The National Research Council study quoted shows 206 watts difference
on high speed, and 330 watts less on low speed.
2) The extra 100 watts used by AC motor is dumped into the house as heat
during the heating months, so it isin't exactly wasted energy from the
point of view of the home owner.
Except when running the AC - and gas is cheaper than electricity for
heating.
3) You can't compare the energy usage of an ECM motor running 1/4 or 1/2
speed against a single-speed AC motor. If you want to compare the costs
of multi-speed operation, then you must compare ECM with a 2-speed AC
motor, and you must correctly estimate the amount of time (total hours
per year) that the fan will be running at fractional speed.
Or do as the National Research Council did, read the study - very
comprehensive testing.
Lifespan of ECM motor is 1/2 to 1/4 that of AC motor, and it's
4 to 8 times more expensive (upfront cost of furnace is higher,
repair costs higher). ECM motors create EM/RFI on your household
wiring, can interfere with tv and radio reception.
ECM motors have the same or greater lifespan,
Totally wrong, because you have to factor in the control or drive
electronics that's powering the motor, and when you do, you'll end up
with burned out transistors.
Actually, they are finding the ECM to last at least as long as the AC
motor in many tests. (in part because they run cooler).
The motor control electronics are the least troublesom of all the
controls on modern furnaces.
SNIP
The pilot light and it's thermocouple switch have proven to be an
excellent design in terms of safety, reliability and durability for
residential furnaces. Do you disagree? Do you have the balls to
disagree?
I do.
I've replaced too many thermocouples on standing pilot furnaces - and
NO electonic ignitors so far on the new furnaces. Average lifespan of
my thermocouples has been less than 7 years (5 in 22 years on my own
furnace, and 5 in 7 years on my friend's gas boiler) I'm on #3 on my
water heater as well.
This is, I believe, year 8 on the electronic ignition furnace.
SNIP
See above. Best case savings is $200 a year, typical savings will
almost certainly be less than $100 a year.
Anyone who lives in a climate zone where they expect to use their
furnace at least 5 months out of the year will realize less than $100
savings in their combined electric and gas bill just by having a furnace
with an ECM motor. Anyone who lives in a more temperate climate zone
and runs their fan more often either alone or in conjunction with their
A/C unit will come closer to the $200 in electricity savings.
The blower in my furnace runs at low speed 100% of the time that the
furnace is not running on high for heat or a/c. (for air cleaner and
overall comfort)
If the furnace NEVER kicked on, the ECM saves me 2890kwh per year.
(330 watts X 24 hrs/day X 365=2890800 wh).That's $232 at $0.08 per
kwh. and that's not counting the savings when the furnace is actually
running. And the actual cost of electricity is more than $0.08/kwh
here when you add in the distribution charges and everything else, and
throw on 13% HST
BTW, I installed a new 3ton, 15SEER heat pump system for a customer
We're talking simply about ECM motors replacing conventional PSC AC fan
motors in residential furnaces. Motors that are part of other
components (heat pumps, A/C compressors, dishwashers, clothes washers,
dryers, etc) are another matter and have different cost/benefit
arguments.
As a consumer, give me the choice of (...)
So you want to go back in time and have your energy bills doubled..
The single largest decrease in my energy bill that the furnace industry
can give me compared to what I have now comes from the 2-stage
condensing heat exchanger. Better airflow design, thinner materials,
stainless, possibly better burner design, etc. All of that comes from
better thermodynamics and materials - NOT ELECTRONICS.
Actually, IF the condensing furnace is 7% more efficient than the
equivalent non-condensing furnace, (97 vs 90) the fuel savings will be
about 8%. With my total annual gas bill of $700 (part of which is my
water heater) my maximum total gas savings would be less than $56 per
year.
Not a very attractive payback, particularly if I end up replacing the
secondary heat exchanger in 10 years.
SNIP