Did I fix this?

[ElectricianJeff]

I went on a service call yesterday that has me wondering.

Two story farm house with large workshop about 200' in rear. House had a 200 amp. service installed about 5 years ago. Garage was fed with a 3 wire 100 amp circuit to a 100 amp MBP.

Home owner had been having problems in the workshop. Furnace and frig, not running right, lights dimming, etc. He said he hadn't had any problems in the house. Sounded to me like a classic neutral problem with the feed to the workshop.

Since I was already in the warm house I decided to start there and didn't even go to the workshop. Pulled cover, all voltages seemed good. However, in moving wires around I could hear something sizzling. A connector had been over tightened on one of the branch circuits and a piece of 12/2 was burning. I pulled the effected cicuit and repaired. The neutral in the romex was pretty cooked.

Headed out to the workshop and everything is working fine now. I did notice that the sub-panel in the garage had no grounding bar. Everything including the ground rod was run to the neutal bar and panel was not bonded.

I wonder how what I did in the main panel fixed the problem in the workshop? I will be going back next week to seperate neutrals and grounds in the subpanel. Is there something else you would check here? Just wondering, thanks

 

[augie47]

a. I doubt your "fix" had any bearing on the garage problem.

b It is possible the 3 wire feed was legal when installed.
(see 250.32)
I see no reason to seperate the grounds and neutral. I would bond the
panel and install a grounding electrode system.

 

[growler]

Home owner had been having problems in the workshop. Furnace and frig, not running right, lights dimming, etc. He said he hadn't had any problems in the house. Sounded to me like a classic neutral problem with the feed to the workshop.

That's not really a classic neutral type problem. If you were to measure a bunch of strange voltage readings and the lights going bright and dim then that would be a neutral.

For a furnace and frig not to work and lights to dim that could be a bad connection on a hot leg of a breaker.

I would start with whatever breaker that feeds the sub panel from the main panel. Pull it and look for signs of arcing. When replacing make sure the connections are tight.

This may be one of those problems that doesn't show up without a load for a period of time to let the connection heat up.

One question: that circuit that was bad in the house, was the breaker next to or across from the breaker that feeds the sub panel? Did you check for signs of arcing?

 

[cowboyjwc]

That's not really a classic neutral type problem. If you were to measure a bunch of strange voltage readings and the lights going bright and dim then that would be a neutral.

For a furnace and frig not to work and lights to dim that could be a bad connection on a hot leg of a breaker.

I would start with whatever breaker that feeds the sub panel from the main panel. Pull it and look for signs of arcing. When replacing make sure the connections are tight.

This may be one of those problems that doesn't show up without a load for a period of time to let the connection heat up.

One question: that circuit that was bad in the house, was the breaker next to or across from the breaker that feeds the sub panel? Did you check for signs of arcing?

I would agree with Growler on this one.

Does sound more like a hot leg issue.

I would also agree with Gus. If there are only three wires pulled to the shop I would just add a ground rod and bond the neutral bar to the can.

 

[220/221]

I don't think you fixed anything.

While you were in the main panel, you should have popped the workshop CB out and looked at the bus behind it, especially if it was by the 20A breaker you fixed.

You need to load the workshop panel, one leg at a time and observe the voltages both on the loaded and unloaded legs. I lieu of testing equipment, a space heater works well.

A significant voltage drop on the loaded leg suggests a compromise/fault on that leg. A significant voltage rise on the unloaded leg suggests a compromised/faulted neutral.

Garage was fed with a 3 wire 100 amp circuit to a 100 amp MBP.

I will be going back next week to seperate neutrals and grounds in the subpanel.

Whatcha gonna do with the grounds? Are the feeders in metallic conduit?

 

[ElectricianJeff]

One question: that circuit that was bad in the house, was the breaker next to or across from the breaker that feeds the sub panel? Did you check for signs of arcing?

I believe it may have been directly above the workshop breaker, I'm not totally sure. No I did not pull but I will next week!

Thanks for all the help, I knew there had to be more to this situation.

 

[jmellc]

Sort of reminds me of a situation where I changed a panel. When terminating neutrals & grounds, I found a ground with voltage on it. Part of a 3 wire ckt with common neutrals. Went to some switched receptacles. I opened what I could in the rooms on those ckts, found no real issues. Could not access some of them because of furniture in the way that 1 person could not move. HO told me she would call me back, that they had a remodel coming up and those rooms would be part of it. Before she calls, I need to make a model of it in my shop; set up a few sw's & recept's & see if I can duplicate the issue. I'm sure it's a lost neutral somewhere on the red ckt. When I turned red ckt brkr off, problem disappeared. A device probably got broken from furniture hitting it.

 

[brian john]

I would

1. Check the source and load panel of the feeder to the remote building and verify all connections are good.

2. Check all branch circuits in the panel for proper termination.

3. Put a DMM on the line termination connections and measure current, and force equipment to start and see if this is a voltage drop issue.

4. Measure voltage drop (VD) across each CB (FOP) under load to check for CB to bus issues.

5. Measure VD at each at the loads with the equipment cyclying.

6. Watch the lights duriing all this for dimming.

7. Check VD from panel to load with loads cyclying.

8. Check VD at lights with loads cyclying.

There may be somethings I am missing, but this should narrow it down.