Motor slowing when electric dryer comes on

There are about 6 houses on the same transformer. So if I upgraded the service, that would help?

Laura

Before you go to the trouble and expense of upgrading your service, you need to focus more on what and where the problem is. Your original post isn't clear about where the slowing motor is... is it in the dryer or a different appliance? Usually, a dryer is on a completely independent circuit, so it would be a good idea to inspect the circuit breakers or fuse(s) associated with the problematic appliances. Measure the voltages at the breakers and/or fuses with and without the dryer running. That should tell the tale.

Be sure you know how to use the voltmeter and be very careful when making the measurements, Ask a knowledgable friend or an electrician to help if you're unsure of what you're doing. The voltages and currents available inside a distribution panel and wall outlets are LETHAL.

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This is actually a followup to an old thread from April/May. It's an air turbine, it consumes about 2 amps. It's very voltage-sensitive, once the electrician measured voltage at the outlet when I turned my electric dryer on, the voltage went down by 2 volts, and the speed went down noticeably. I just got it put on its own circuit, so I'm sure the circuit breaker is OK.

So I was thinking of measuring the voltage at the outlet. Is this reasonably safe?

Could the voltage at the outlet be varying more than the voltage at the weatherhead? The recording voltmeter was recording voltage at both sides. Could uneven load cause the voltage at the outlet to change more than voltage at the weatherhead?

Laura

I had to do that last summer as part of a new heat pump with electric heat backup. Cost $1500 up front for the power company to upgrade the transformer. There are a total of 3 houses on my transformer.

Where do you live? I am really surprised that the power company would put 6 houses on the same transformer. Houses must be located pretty close together.

Paul

Maybe that's the problem. I get the impression that many of the changes in speed in the air turbine are being caused by other people's usage. I live in upstate NY.

So is it possible for an unbalanced load to cause the voltage at an outlet to be different from what the power co. measures at the weatherhead?

Do any of your lights become _brighter_ when the dryer turns on? If so, you may have a problem with the neutral.

Cheers

Phil Hobbs

Could a problem with the neutral cause voltage fluctuations at an outlet, that don't appear on the weatherhead? I have fluorescent lights. Occasionally they flicker off. This happened on May 27, and it didn't seem to show up on the utility co's record of my voltage.

If I have a problem with the neutral, would it be inside my house, or a utility co. problem?

When I had incandescent lights, they did flicker sometimes. Not terribly often, though. Is it worth it, to get a voltmeter to see how much the voltage is changing at the outlet where the air turbine is plugged in? Can that voltage be different from what the utility co. measures?

Yes, the voltage at an outlet can vary more than at the weatherhead because there are seveeral wire connections in the line before getting to the outlet. First, there's the breaker panel where the breakers tap off the main line from the weatherhead. Then, there's the wire that connects to the load side of the breaker. Then, there are one or more connections that split off to multiple outlets. Any of these connection points could be causing a voltage drop if any of the wiring connections are loose or if the wire is too small for the service. In either case, there exists the possibly of overheating and fire.

Having said all that, your statement that an electrician measured a 2-volt voltage drop at the outlet when the dryer turned on leads me to another thought. What gauge wire is used to supply the outlets? Normally, a 15-amp circuit should be wired with 14-gauge copper wire or 12-gauge aluminum. Is it copper wire or aluminum? If it's aluminum, you really should have someone check all of the outlets in your house to make sure the screws are all still tight. I used to live in a house in Florida (built in 1976), that was wired with aluminum wire, but the ends of the wire was stuffed into the quick-connect hole in the receptacle. I had trouble almost from the day I moved into the house with arcing, sparking, and smoke coming from the outlets. I had to pull out every receptacle in my house and put the wires under the screws, as they should be. It could be that the turbine motor is just very sensitive to voltage change, and nothing short of replacing the motor or the entire turbine unit will fix it. Did the electrician tell you what the actual voltages at the turbine were, with the dryer running and not running?

Almost any digital voltmeter that you buy today (even the cheap ones from the likes of Harbor Freight, such as the one here

I'm not an electrician, but I believe that most houses in the US have two-phase service, and that the neutral is bonded to the ground rod near the service entrance. Voltage drops in the neutral make one side go down in voltage and one side go up.

Cheers

Phil Hobbs

The voltage at the turbine outlet goes up by about 1 volt when the 1 kW microwave goes on. They're on opposite sides of the service. Is this a significant amount?

(...)

Nup. Single phase, center tapped. :)

Yup.

--Winston

so,

=20

That is still single phase service.

?-)

so,

It does indicate a problem developing. =20

?-)

Only to the extent that the unbalance is internal to your house. Which may explain all of it or not, seriously have your neutral wiring checked as well.

?-)

f so,

As Winston said. Here's how Phil H. is correct:

Household electricity 101: Residences get single phase 240, split into two 120 leads and neutral. Stoves and dryers get the full 240, other appliances get 120 VAC. If the load on each 120 VAC lead is the same, no current will flow on the neutral.

If, the loads on the two leads are different, and current flows on the neutral, AND the neutral is resistive, then the voltage on the more heavily loaded leg will be less by the amount of the voltage drop on the neutral. Which means the voltage on the more lightly loaded leg will be more, by the amount of the voltage drop on the neutral.