What kind of motor is this in my furnace? Need to replace

LegendsCreek

My energy monitor is telling me this furnace motor is using 350 watts every time it runs, which is often in the winter. The motor is the fan motor which turns the belt that pushes the hot air through my ducts. Its got to be at least 30 years old.

I would like to replace it with a new motor that uses far less energy and I was wondering how I find out exactly what replacement I need? Thanks a lot.

Jamie Hall

First place, 350 watts isn't much for a fan motor. It takes a certain amount of power to push the air around in the ductwork, and you can't escape that.

So... it's unlikely that a new motor will use much less power. A new design might save as much as 30 watts... maybe... but it's unlikely.

That said, any motor which has exactly the same shaft size, extension, and keyway, and the same mounting style and dimensions, and the same rpm and output power rating and voltage and phase would probably work.

Bottom line? If it's quiet and working, I'd leave it alone and accept the power use as one of the many downsides of scorched air heat.

STEVEusaPA

And keep replacing that filter, at least monthly. Yeah the only way to save energy on that would be:
-Solar panels, lots
-Storage batteries, lots
-Power inverter

SWEI

You should be able to find a direct ECM replacement, which would save far more than 30 Watts.

At that age, replacing the furnace would probably be a better option.

LegendsCreek

I was thinking about ECM and my bet would be I would save more than half the wattage. I bought an energy monitor in October and have replaced everything that I could see was using a ton of energy with more efficient devices/pumps/lights/motors. My electric bill is half of what it was this time last year as a result.

So I should take a look at the exact specs on the current motor and try to find a direct replacement to that?

As for replacing the furnace, that is not an option. The burner on the furnace is now my backup heat source as I am using a wood boiler for heat. The only thing this furnace is doing when running is blowing the hot air from the wood boiler through my ducts, and not burning oil at all unless it falls below a certain temp.

SWEI

The specs that matter most are the size (in HP), the voltage, the RPM and the mechanical dimensions.

The ECM should have four or five speed taps on it -- you can generally supply 24 VAC from the stat to the tap you want to use and leave the AC power on all the time. Some of them have the power onboard and you just move a jumper. Unless they are using 24 VAC to do that, you will need to switch the AC supply with some kind of relay (just like the old motor has.)

ChrisJ

@SWEI
I may be mistaken, but I thought those ECM motors sold for something like $600-800?

LegendsCreek

$600 is a ton of $$!! I might have to consider eBay if I can even find one that will work with my furnace.

SWEI

Should be nowhere near that price, unless it's several horsepower.

LegendsCreek

I am attaching 2 photos I took of the label. It was very hard to get in there and get a clear one. I don't quite understand them or how to use this info to match to an ECM motor but I believe its HP .33, Voltage 115, and RPM 1725 . Do you make anything of this?

SWEI

That's a 1/3 HP blower motor. Many ECMs start at 1/2HP, but since they're variable speed they can cover multiple sizes.

e.g. https://www.marsdelivers.com/products/39/HVAC/

Sailah

Something like this is what you have

The 48 is the NEMA frame size, you have a 115v , 1/3 HP 1725 motor. Very common. Looks like full amp draw is 6.2 A so full load is 120v x 6.2A or 744 watts. Your reading of 350 seems normal.

http://www.supplyhouse.com/Marathon-Motors-H165-Fan-Blower-Motor-1-3-HP-1725-RPM-1-PH-CCW-115V

Staying in this class of motor won't lower the wattage. If the bearings are bad in your motor that's one thing. But if it's quiet and runs, I'd leave it alone.

The ECM motors look like they are mostly direct drive vs yours which has a pulley.

I know enough about motors to be dangerous and that's mostly 3 phase stuff from wiring my machine tools

http://www.supplyhouse.com/Genteq-Motors-19790000

LegendsCreek

Thank you very much for the links and the info. I looked around the internet and I don't see a single ECM motor that is belt drive. Lots of direct drive like the links you all sent but I don't think they will work the same.

Upon considering just replacing the motor with a newer PSC motor I don't think it will lower my energy costs. I went over to one of my workshops and plugged in my honey extractor which uses a belt drive motor with the same exact specs as the furnace blower motor I want to replace and it used 550 watts!! If I try to replace the old motor it might use more energy than the 350 watts my old one uses.

There has to be a solution. haha.

Jamie Hall

LegendsCreek said:

There has to be a solution. haha.

I hate to be the bearer of bad tidings, but...

There ain't no free lunch, however green one wants to be.

Which, in your situation, translates into if you want to move x cubic feet of air per minute through ductwork with a resistance of y, it is going to take a certain amount of power. Like... about 350 watts, in your case.

Now you could reduce the power draw in one of two ways: reduce the amount of air you are moving or reduce the resistance to that air movement.

ChrisJ

Jamie Hall said:

LegendsCreek said:

There has to be a solution. haha.

I hate to be the bearer of bad tidings, but...

There ain't no free lunch, however green one wants to be.

Which, in your situation, translates into if you want to move x cubic feet of air per minute through ductwork with a resistance of y, it is going to take a certain amount of power. Like... about 350 watts, in your case.

Now you could reduce the power draw in one of two ways: reduce the amount of air you are moving or reduce the resistance to that air movement.

I vote for new duct work.

LegendsCreek

Haha. I guess its just a case of wishful thinking. My ductwork is not an issue and the amount of air is fine. I was just hoping that maybe there was a better motor where I could get the same for less.

SWEI

Tough to find an ECM that's set up for the axial loads of a belt drive -- and a V-belt consumes a fair bit of energy just for itself.

EBEBRATT-Ed

If you can stand less air flow you could adjust the adjustable sheave (you probably have one on the motor) on the blower motor and open it a bit and see if your wattage drops. You need to re-tension the belt after doing this.

BEWARE; if you do this and reduce the airflow the furnace may trip your high limit control if you use the back-up burner in the furnace

Gilmorrie

The power (watts) delivered by a motor depends upon the mechanical load on the motor, which is equal to the motor speed times the delivered torque. Changing motors won't materially change the watts, except that a more efficient motor will consume a bit less electrical power to deliver the same mechanical load.

A garden-variety fractional horsepower motor will typically have an efficiency of about 80%. By spending more money, you could perhaps improve that by a few percentage points. But, basically, swapping motors is not going to reduce electric power consumption by much, if any. Motor losses include friction, windage, winding resistance, etc.

Measuring motor electrical power consumption is a little more complicated than multiplying volts times amps. An a.c. motor's amps and volts are not in phase, so VxA will be higher than the motor watts - because of the power factor. Measuring motor power requires a wattmeter. I doubt that your energy monitor is giving you the true watts.

Let's assume that you could somehow reduce your motor's power consumption by 20 W, which I think would be optimistic. If the motor runs for 2,000 hrs/yr, that would save 40 kWh. If you pay $0.15/kWh, that amounts to $6/yr. To achieve a 5-year payback period, you could afford to pay $30 for a replacement motor. Not very likely.

Solid_Fuel_Man

If you really want to save money.....get rid of the ductwork and go hydronic. Moving heat via water consumes much less energy than via air. I know this is out of the question, but someone had to say it.

You can move all the heat a wood fire can preduce with less than 50 watts, all in.

But you'd spend more $$$$ than you'd save on electricity in a lifetime.

Taylor

SWEI

Gilmorrie said:

A garden-variety fractional horsepower motor will typically have an efficiency of about 80%.

Please cite references for this.

hot_rod

Now with hydronics we could probably move that load with 17- 27W circulator in a 3/4- 1" tube

LegendsCreek

Thank you very much for the excellent information. I have a much better understanding now of how these motors work.

Hydronic will be what I convert to when I am ready to replace the furnace. I would much rather go with a forced water system and I am much more familiar with them as my houses are on the same wood boiler and have forced water, but for some reason the previous owner put forced air into both workshops.

Big Ed_4

Old Belt drive unit , I would have to assume its over twenty years anyway ... The fan speed should be adjusted to the manufactures design of Delta Temperature ... Why not replace to a staged condensing furnace assuming you use gas for fuel