Ask Me Help Desk - Voltage okay- yet lights still dim

Forgive me if Ive ask this question before, I think I wrote it out, but had to leave and I just closed it rather than posted.

Two years ago when I had my 15KW electric furnace installed, I noticed that when ever it would run, it would make the lights dim, and they wouldn't get bright again until it cut off. The same goes for fans, you can hear fans slow down (such as the bathroom fan, and the fan by my bed)

Now I had one problem where I was tripping the breaker for my furnace, as the unit was under warranty, I just let them deal with it, turns out my furnace is drawing about 46 AMPS (if memory serves) and they wired it to a 50 AMP breaker, as the wire was already rated for 60 AMPs, they just swapped the breaker and I haven't had a problem since.

The man did tell me that my voltage at the box was to low, which was causing the furnace to draw excessive amps. I remember his reading at the lugs were about 232 volts. He said I needed to call the power company and tell them to check the transmormer. So I did, they came out and checked it and said everything was okay, so I didn't worry about it anymore.

About 6 months ago, I noticed they changed our transformer. This was during the summer, so I didn't see what difference it made on my lights dimming. Well, now that we are in the heating season, there is no change in my dimming problem or fans slowing down.

It should also be noted that I share a transformer with a neighbor.

Now last night, I got into a conversation with an electrician who said that my low voltage needs to be fixed, this can ruin my elements and burn up the motors in my fans. It also drawing excessive current and consuming extra electricity. I agree'd.

Well that is, until I got home, and for the first time since the new transformer was installed, actually tested my voltage. Turns out that now at the 240 AC receptacle I now have about 250 volts!

So my question is, if Im getting 250 volts, why are my lights and fans still slowing down? And will this hurt them/shorten their life?

The stats of the electric system are as follows:

I have one 200 AMP murray box in the basement. Its about 200 feet from the transformer. The house is 60 years old, so Im sure this box is an upgrade. At my AC outlet there is 250 volts. The furnace is 15KW, split between two breakers, one 60 and one 30 AMP.

What is the solution for this? This can't be normal. I have been in so many huge kitchens with 100 AMP electric fryers, ovens, etc, and their lights don't dim while they are cooking...

THe issue is the 200 foot away from the transformer, line loss, the heavy load of the elements is causing the voltage drop to show up.

Low valtage is not going to ruin the elements, but will damage motors.

Ask, demand, the utility to come out and do a voltage drop analysis, they use a device that plugs in place of the meter, and applies a 1500 watt load, and they measure the Vd.

Ask them to tell you exactly what size and type wire is being used.

Is the utilty feeder underground or overhead? Who is responsible for it, the utility or the owner?

This can also be caused by loose or corroded connections anywhere from the transformer to the panel, in addition to the long line.

All the utility lines are overhead.

I've always though that the electric company is responsible for everything to the meter and the customer is responsible for everything past the meter, including the meter plug.

However I have been told that if the incoming supply line from the meter to the transformer needs to be upgraded I have to pay for it.

American Electric Power is my power company (also known as Appalacian Power locally) maybe someone here knows who pays for what with that company.

They furnish and install overhead lines to your home, see section 5.01 of their requirements:
https://www.appalachianpower.com/glo...vice_Guide.pdf

It is not clear to me who is responsible to maintain overhead lines. Hmmm.

The size of the overhaed line should have been sized according to your connected load. Did you advise the utility of the electric heat you have?

Oh, an after thought, a 15 KW load at 240 volts draws 62.5 amps, and NEC does not allow a breaekr/circuit for electric heat larger than 60 amps, therefore you should have two 240 volt circuits for your electric furnace. And, if you only have one circuit, the 60 amp circuit breaker is still too small. What size wire/feeder is going to the furnace?

Quote:

Originally Posted by tkrussell

Oh, an after thought, a 15 KW load at 240 volts draws 62.5 amps, and NEC does not allow a breaekr/circuit for electric heat larger than 60 amps, therefore you should have two 240 volt circuits for your electric furnace. And, if you only have one circuit, the 60 amp circuit breaker is still too small. What size wire/feeder is going to the furnace?

I have two breakers. I have my first 10KW set of elements on a 60 AMP breaker, and my other remaining 5KW boost element is on a 30 AMP.