Furnace Fan "auto" vs "ON"

I've had my fan switch set to 'on' for the last 15 years. Costs a little more than a 100 watt light bulb to run, but stopping and starting is worse for an air cooled motor than leaving it on. Make sure you keep the air filter clean. You'll sleep better, and the temperatures will be more even.

It is to be used by a service man.

Are you sure about that? I think mine draws about 5 amps.

but stopping and starting is worse

Any and all if thats what you want.

Mine only gets shut off for service. Other than that, the fans on 24-7.

I think leaving the blower running 24/7 will wear out the bearings much faster and use electricity...

leave it on AUTO unless you need the added ventilation.

Mark

I tend to leave the fan running continuosly more in the summer time than in the winter. But I think the motor draws more juice than a 100W light bulb. If you have a 3/4HP blower at the very least it uses 5 amps.

How many HP is your blower?

Are you sure your not referring to the combustion blower motor?

Ive got a 1/2HP on mine, its pulling about the same...but then, load, due to the duct design, will play into this, and most people do not clamp a meter on, close the door, and take a peak reading with the blower under load.

LOL! Bob, you're either leaving out some relevant facts, or you're lying, I'm not sure which! Also, most fan motors aren't continuous duty in the way you're claiming to use them.

What's missing from your post? Or are you just full of it?

Pop

: > I think when you keep the fan "ON" the fan will run contineously while : > on "auto" it will start and stop automatically as per the need. : >

: > Does anyone know which weather condition you should keep the fan to : > "ON"? Thanks in advance. : >

: :

Air-cooled direct-drive blower motors can be run all the time, but you should have a properly sized duct system, and keep your filter clean. It's much worse to stop and start them all the time. Once those motors get going, they have very little strain on them.

Could you explain why?

The bearings are being worn whenever the shaft turns. What typically breaks on these,....... the bearings.

What wear is caused by starting and stopping the motor? These typically do not have a centrifugal switch or anything like that so what's the problem with starting and stopping?

On a normal winter day my furnace and blower run

The last 2, 100000 btu furnaces Ive had pull apx 375 watts on a direct drive blower. that will cost anyone at .125kwh a standard US rate apx

At the classes I've gone to, the teachers said that stopping and starting was worse, and that once they get up to speed, there's very little strain on a motor of this type. I don't remember anyone ever asking them why. I always assumed it was from the heat generated while the armature was straining to get up to speed but still didn't have enough air flow to cool it properly. As for the bearings, I don't know if sleeve or ball bearings makes a difference, but I assume the blower wheel must be balanced properly to cause minimal bearing wear.

My (gas) furnace consumes .14A with the fan off. 6.9A with it on. That's with no heat.

And the filter will need cleaning more often.

They make direct drive blower motors that draw less than 1 amp at 230 volts, but I've never seen a 115 volt motor on a furnace that low.

I used a plug-in meter (kill-a-watt) on the furnace power cord, when I read 6.9A.

but it takes only a few seconds to get up to speed...

I find it hard to believe that any significant heat builds up in 5 seconds compared ot the heat that builds up runnning 24/7....

Imagine starting the blower..... then as soon as it gets up to speed, stopping it, and checking the motor windings and armature temperature .... compared to letting it run all day then checking the temperature..

thanks

Mark