100-ish service, 60amp sub, lights flicker on load.

[madosta]

Not mine, but a friends.

He has an older house at the end of an industrial district, only house on the street. The main high voltage is huge 3 phase awesomeness powering these factories. His house is fed with one line from this to a small transformer and I don't think there is a neutral back up on the pole, just one wire crosses the street and the guy/tension wire a few feet down the pole.

Transformer looks small, only a single house application.
Weatherhead and mast, to the meter, then to a disconnect, then 50 feet of SER to the panel through the walls of the house.

The 60amp sub is in the garage and when he welds or does some things the lights will flicker a little. Two ground rods.

I thought open neutral or something like that, turned on a hot plate full bore on a few different recepts and it wasn't reproduceable.

Put my meter on each leg while doing this and it was 120v +- 2v and the other was 116v or so.

It doesn't seem to be a grounding issue or a neutral issue except at the meter or pole... not sure how it works.

What else can I check or confirm?

 

[volleyball]

Check for corrosion at the connections. Is you voltage measurement done with no load?

 

[madosta]

Voltage drops on one leg when load is applied. 120v with no load.

 

[sberry]

The 60amp sub is in the garage and when he welds or does some things the lights will flicker a little. Two ground rods.

I thought open neutral or something like that, turned on a hot plate full bore on a few different recepts and it wasn't reproduceable

Not saying there isn't a problem with an old electric system but 100A daisey chained for a long ways with welding or air comp on and the lights flicker a little?

 

[wyliesdiesels]

Not mine, but a friends.

He has an older house at the end of an industrial district, only house on the street. The main high voltage is huge 3 phase awesomeness powering these factories. His house is fed with one line from this to a small transformer and I don't think there is a neutral back up on the pole, just one wire crosses the street and the guy/tension wire a few feet down the pole.

Transformer looks small, only a single house application.
Weatherhead and mast, to the meter, then to a disconnect, then 50 feet of SER to the panel through the walls of the house.

The 60amp sub is in the garage and when he welds or does some things the lights will flicker a little. Two ground rods.

I thought open neutral or something like that, turned on a hot plate full bore on a few different recepts and it wasn't reproducible.

Put my meter on each leg while doing this and it was 120v +- 2v and the other was 116v or so.

It doesn't seem to be a grounding issue or a neutral issue except at the meter or pole... not sure how it works.

What else can I check or confirm?

First of all, a 120v/240v transformer will have 2 bushings/inputs. The second input is probably connected to a ground rod at the base of the pole. Its using the earth as a neutral/return path back to the substation. This setup isnt very common except in rural areas where substantial savings on wire can be had because only 1 wire is ran from pole to pole.

This type of system is called single-wire earth return:

http://en.wikipedia.org/wiki/Single-wire_earth_return

It wouldnt be a grounding issue since electricity, under normal conditions, doesnt flow on EGCs/grounds. The exception to this is the subpanel could be fed via a 3-wire feeder(2 hots and a neutral), the neutral developed a bad connection and electricity found an alternate path back to its source via a parallel conductive path between the garage and the house. However, the conditions u describe doesnt show to be a neutral issue. This is because when a neutral is bad you will see one leg(unloaded leg) with a higher voltage to ground or neutral and the other leg with a lower voltage to ground, both adding up to ~240v.

Is the welder 240v or 120v? how many input amps? What is the size of the feeder wire going to the garage and how long is it?

This leads to my next idea, which i go into below.

Voltage drops on one leg when load is applied. 120v with no load.

So the voltage only drops on one leg with a load and not the other leg while under a load?

Youre gonna have to track it down before calling the PoCo. What i would do is turn on the same load that it happens with, go to the main service panel, and measure the voltage between each leg and neutral and between both legs. If no drop then this tells u that the issue is somewhere in the feed going to the garage. Could be high resistance/bad connection, etc. If the voltage drop IS present at the main service panel, then this tells u that the issue is either in the service entrance wire in the mast, the PoCo's service drop, the transformer, or the high voltage feeder or neutral connection at the primary bushing of the transformer.

This happened to me one time. I had voltage drop on one leg that would cause some lights in the house to dim when I ran the garbage disposal. I left my meter probes clamped to the bus bar and neutral, set it for 'hold' on the 'min' reading and left it there over night. Voltage would drop as low as 100v on the bad leg. Called the PoCo, they came right out, discovered one of the splices(had 2 service drops spliced together at a pony pole) was REALLY HOT and had a bad connection. He added another splice without disconnecting the bad one and that fixed the issue.

 

[sberry]

I had one at a Buds, called the poco twice,,, when windy,,, finally one day one of the conductors falls off in the parking lot.

 

[bczygan]

I'd get the POCO to run me some nice 3PH!

......Or here in Detroit, I'd just get some jack leg street guy to hook it up!

 

[madosta]

Electrician coming out tomorrow I guess to go through the meter and the disconnect.

I can't believe the neutral would be earth, but I see no other wires. I'll have to take some pics.

I'll let you know what the electrician discovers.

 

[wyliesdiesels]

Electrician coming out tomorrow I guess to go through the meter and the disconnect.

I can't believe the neutral would be earth, but I see no other wires. I'll have to take some pics.

I'll let you know what the electrician discovers.

Why bother calling an electrician just uet. U could do the investigating yourself and save money.

And yes, the earth can be used as a neutral. Did u read the link i posted above?? Look at the primary bushings of the transformer which are typically on top. One of them connects to the single high voltage primary wire up top. The other bushing should connect to a bare wire that is stapled to the pole and runs down the pole to a ground rod at the base.

 

[volleyball]

It's not his money, this is for a friend. And if you are not comfortable playing with service lines, it is best to call someone.

 

[madosta]

Electrician friend confirmed what I did. 115v on one leg. Called DTE (LPC) to come investigate. Old transformer and **** connections. Yes Wylie I read what you said and it's spot on.

 

[wyliesdiesels]

Electrician friend confirmed what I did. 115v on one leg. Called DTE (LPC) to come investigate. Old transformer and **** connections. Yes Wylie I read what you said and it's spot on.

Where are the bad connections at? Are they going to fix it?

 

[madosta]

Ok, looks like a tree limb at one point fell on the overhead lines and loosened the connections at the connection to the service.

Go figure!

 

[AlwaysFixingSomething]

Why bother calling an electrician just uet. U could do the investigating yourself and save money.

And yes, the earth can be used as a neutral. Did u read the link i posted above?? Look at the primary bushings of the transformer which are typically on top. One of them connects to the single high voltage primary wire up top. The other bushing should connect to a bare wire that is stapled to the pole and runs down the pole to a ground rod at the base.

 

[theoldwizard1]

Electrician friend confirmed what I did. 115v on one leg.

115V by itself is not a real issue. What was the other leg at ? If the difference is less than 10% it is hard to get the POCO to come out.

 

[madosta]

I'm not 100% but I think he said 124v on one and 106v on the other or something like that. He said the difference was bad enough. He does a lot with the poco I guess.

 

[sberry]

You got to wonder how many zillion connections like that there are, they are not uncommon. Someo f this has been in service a long time.