Electric motor/circuit question

[BCDrums]

We have a treadmill so that we can exercise during the cold months in the Northeast (current temperature is 13 degrees). The motor in the treadmill failed and was replaced under warrantee.

The manufacturer recommends a dedicated 15 amp circuit for the treadmill. We have it on a circuit with our TV and stereo. The technician who replaced the motor said that it may have failed because we didn't have a dedicated circuit. Might this be true?

I would have guessed that if the circuit was overladed the breaker would blow.

Thanks for your comments.

BC

[Joseph Meehan]

I would think it would be more likely to damage the TV or even more likely to cause interference with the TV.

I assume you are not running it off an extension cord. If so that could have been the cause as it may have been reducing the available voltage.

I have three circuits in the converted bed room where I have mine. One for the A/C one for the treadmill and one for the rest of the room including TV. Mine is a heavy duty DC job.

[Bud--]

I agree with you.

-- bud--

[tom]

Break out the cross-country skis? 13 degrees is a good waxing temperature. Tom

[Toller]

Well... unless you had a very long circuit it would not matter. And, as someone said, it would affect the TV more; assuming you had both on at the same time. If you don't have the TV on, it is a dedicated circuit.

If you had a very long circuit (opposite corner of the house from the panel,

3 stories apart...) you could have had excessive voltage drop, and that might have caused the motor to fail. It is most unlikely, but if you want to test it, turn the treadmill on while watching the voltage with a volt meter. If it dips significantly, you might need a heavier cable.

[gfretwell]

The "technician" is a moron

[LayPerson Tom]

imho:

I've heard of this, but not on motors, but electronics. It's called soemthing like 'voltage frequency quality'? It's where the componets are designed for a perfect sin wave at a specfic voltage quality. As you deviate from this, you lessen the life span of the equipment.

As for the breaker, you hope that if the circuit is overloaded it would trip.

Just a guess....

tom @

[BCDrums]

It's about a 35' run from the panel to the treadmill. And I ALWAYS have the TV and stereo on when I'm using the treadmill- it is a tedious way to exercise!

I put the probes of a multimeter into the outlet into which the treadmill is plugged, which is downstream of the TV/Stereo. The meter didn't move when the TV and stereo powered up. Then I turned on the treadmill and took it up to our usual speed. Again, the meter did not move. Is this a valid test for voltage drop?

Thanks for the help. BC

[Toller]

If it showed 120v and didn't drop when you turned the machine on, you are in good shape.

35' is certainly too short a distance to have substantial voltage drop anyhow.

Many treadmills have DC motors and don't have starting spikes. Your test suggests you have one like that. Like someone else said, the tech was crazy.

[George E. Cawthon]

The answer is NO. The suggestion of using a dedicated circuit is for the purpose of protecting other appliances from voltage changes when the motor starts or shifts power.

[BCDrums]

Thanks to all for setting me straight on this!

BC

[mm]

I would do the test again with you on the treadmill and someone else watching the meter.

Although you can't do that because the motor isn't strong enough to work the thing now, iirc, right?

Then do it after you get the new motor.

BTW, does the plug get hot after you're on the treadmill. It shouldn't, and I suppose if it does it is reducing the voltage. I had a 40 year old receptacle and a 15 amp space heater in my bedroom, and woke up in the morning to find a 1 to 1 1/2 inch flame coming from the plug. The plug got hot, and I don't know if it reduced any voltage but it ignited itself. Fortunately the flame went out after I pulled the plug out. I don't quite know why.

[mm]

Low voltage will burn out a motor if the motor stalls because the voltage is too low. In that case, instead of turning the electcity into motion and some heat, it turns all of the current into heat. (although I think the current flow lessens because of induced reverse voltages, or whatever they are called. When the motor is stalled, i think it doesn't use as much current, but all the current it does use is turned into heat.)

AFAIk in practice this usually happens with compressors, but any kind of motor which stalls is capable of doing this. I'm lucky the little fan in my refrigerator didn't burn out when a mouse got stuck in it, and the blades didn't turn, for about 3 weeks, but maybe even the extra heat wasn't enough to melt anything.

A tread mill motor is going to be a lot different from my little fan.

[Tony Hwang]

Hmmm, Analog or Digital meter? What is the display rare of the meter? Maybe too slow to show the fluctuation. If motor is under powered it'll rowl a lot and it won't run at normal efficiency. Isn't TV screen flicker when motor is turned on?

[gfretwell]

Treadmills usually have a DC motor and they woul;d only run slower if there was a voltage drop. It certainly wouldn't hurt the motor. The speed control is pulse width modulation that basicaqlly works like a dimmer, picking off pieces of the sine wave before it gets rectified.

[BCDrums]

The tech was there to put in the new motor, so we are up & running, literally!

Will check.

BC

[BCDrums]

It took two years of wintertime-only use for the treadmill motor to quit, and it never stalled in the sense of being on but unable to turn. It just quit one day. Had been making a squeaking sound for quite some time before that.

BC

[BCDrums]

It's a cheesy old Radio sHack analog multimeter. I couldn't even figure out which of the many scales I was supposed to use, but the needle did not budge as I turned on the TV, big stereo, and finally the treadmill. The TV has never reacted when the treadmill starts or runs.

[Dave Martindale]

No, it's the other way around. A stalled motor draws *more* current than one operating at full load at normal speed, and that (combined with no cooling) is what burns it out. The induced reverse voltage is what reduces current when the motor is running.

On the other hand, the fan motor in your refrigerator is probably a shaded-pole motor. These are pretty inefficient even when running, and are often deliberately designed so they can be stalled without burning up.

Dave

[Mark Lloyd]

I remember it being called "back EMF", and it is generated when the motor is moving.

A stalled motor draws MORE current, similar to a prolonged startup.