Improper voltage

[Sparky_ron]

So I have a dilemma and I’m looking for direction. Today I went to a customers business and they were having voltage issues. There is a fusable 400a 3-phase main disconnect, followed by a buss gutter. Im getting 208-210 a to b, b to c, and a to c, on the line and load side of the fuses however, I’m only getting 108 V on A, 135V on B, and 110 V on C.(phase to ground and phase to neutral.) With the fuses removed, I get 120 V on each phase on the incoming power side so I know it’s not a transformer issue. I also checked continuity on all three fuses because I didn’t have my fluke with me, (they are dual element fuses) and all appeared to be good. I have not opened up the gutter yet. I plan on going back tomorrow with my meter. What else could be causing the voltage to go so wonky with the fuses installed? Any help would be appreciated thank you.

 

[infinity]

Sounds like a bad neutral somewhere.

Welcome to the Forum.

 

[LarryFine]

Welcome to the forum.

Try testing across each fuse, line-to-load, while the load is on.

 

[Sparky_ron]

Welcome to the forum.

Try testing across each fuse, line-to-load, while the load is on.

You mean line side of A to load side of B etc.?

 

[LarryFine]

You mean line side of A to load side of B etc.?

No, line side of A to load side of A, etc. You should read no voltage.

A good fuse, like a closed switch, should have 0v across it,

 

[Sparky_ron]

No, line side of A to load side of A, etc. You should read no voltage.

A good fuse, like a closed switch, should have 0v across it,

Gotcha I understand. Eliminates reading backfeed

 

[Sparky_ron]

*PROBLEM SOLVED!
So I checked the fuses and all three were good. (Thank you Larry) Infinity, you were correct. The line side neutral was extremely corroded on the lug so I backed it out, cut the wire, re-stripped it and re-landed it in the parallel lug next to it, torqued it down, re-energized it, and the voltage went back to normal. I suspected the neutral also but couldn’t do anything about it until I could shut down the load. It’s always the damn neutral lol.
Love the forum!
Thank you for your input,
Ronnie
Bolt Electric - San Antonio

 

[infinity]

*PROBLEM SOLVED!
So I checked the fuses and all three were good. (Thank you Larry) Infinity, you were correct. The line side neutral was extremely corroded on the lug so I backed it out, cut the wire, re-stripped it and re-landed it in the parallel lug next to it, torqued it down, re-energized it, and the voltage went back to normal. I suspected the neutral also but couldn’t do anything about it until I could shut down the load. It’s always the damn neutral lol.
Love the forum!
Thank you for your input,
Ronnie
Bolt Electric - San Antonio

Glad to help. Your voltage readings were indicative of a bad neutral. Happy that you were able to locate and fix the problem.