Unbalance voltage in garage

[bentroof]

I've got an issue with my voltage in my garage. I recently installed wiring in this new garage. It has 3 wire to it (existing power to an old garage), two hots and neutral. I wired the garage panel as if it were a main, ground rod, and bonded (in my box, the neutrals and grounds are together).
The wierd issue is the voltage will increase on one leg for some reason to something like 170v on one and 109v on other. It is hardly noticable in the lights, unless I hit the garage opener, it won't operate. Then if I turn the air compressor on, it will start off slow then run properly. For some strange reason, the voltage will go back to around 118v on each leg after the compressor runs. I discovered this fix by accident. It is so intermittant is it hard to find.
I am thinking I have a short somewhere. I am not sure if it is in garage or if it is in the line from the house. I check the voltage at the load center in the house and the voltage is only unbalanced for the garage, not to anything else in the house.
I intend to run 4 wire to garage this summer, when the ground isn't frozen. I plan to install a pedestal at garage then run power to house and upgrade to 200a service. The house needs a new load center anyway.
Sorry for long explainatiion, but this one is really hard to figure. I hope someone has a good starting point.
Thanks

 

[rlitman]

Sounds like a loose neutral to me, but the three wire could be part of the problem too. It is supposed to be done with four wires.

 

[1/2 Cup]

I would look for a loose connection or faulty breaker first up.

 

[walrus]

Its a neutral issue somewhere, loose, broken, bad connection somewhere

 

[tdkkart]

Yup, loose or broken neutral, just had it in my house 2 weeks ago, came home from work at 1am to find all kinds of weird **** going on. Smoked my furnace, Dish receiver, one of my garage door openers, Sleep Number bed pump. I was seeing 80V one leg, 160 on the other.
Right now we're running with a temporary neutral on top of the lawn till the groudn thaws out.

 

[bentroof]

Thanks for the suggestions. I was leaning towards the neutral being the problem. The wiring to this garage isn't ideal, I plan to update the power to house and garage when things aren't so frozen.
Could I have issues with the neutral in outlets? Such as, loose wire or something. I put in GFCI outlets at the beginning of all down line outlets. Those don't seem to be affected or none have tripped anyway.
I wired the power from house to garage the same as it was before, but evidently it isn't right. I will check all the connections and am thinking about installing a new temporary neutral. The neutral needs to have the same current carring capacity as L1 and L2 correct? The ground can be smaller, right?

Thanks!

 

[rockwithjason]

is this garage fed from your house panel or another panel or is it on it's own service? if it is NOT on it's own service you need to remove the boding screw that bonds the neutral to ground in the garage panel. other than that i agree that it's a loose or broken neutral. check all of the lugs and connection points in both panels

 

[bentroof]

is this garage fed from your house panel or another panel or is it on it's own service? if it is NOT on it's own service you need to remove the boding screw that bonds the neutral to ground in the garage panel. other than that i agree that it's a loose or broken neutral. check all of the lugs and connection points in both panels

The garage is fed from the house, but only on 3 wires (2 hot-1 neutral). The garage box is grounded and bonded. It sounds like I should NOT have it bonded.

 

[wyliesdiesels]

You definitely have a bad neutral connection between the house and garage if the voltage at your meter main/main service panel is ok(120v per leg!) Does the feed to the garage run underground? If it does and if the neutral connections in both panels are good, then u might have a break in the neutral somewhere underground!

The garage is fed from the house, but only on 3 wires (2 hot-1 neutral). The garage box is grounded and bonded. It sounds like I should NOT have it bonded.

All subpanels should have the neutral bus bar insulated from the panel enclosure and should not be bonded to the ground bar! If there's a bonding screw, wire or strip connecting the neutral and ground bus bars together in the subpanel, remove it.

 

[bentroof]

Found the problem on the neutral.
My power is run overhead and the neutral line is saddle clamp (don't know if that is right wording) was corroded. I replaced the clamp and the voltages on each leg look a lot better. The load is a bit unbalanced on the legs, but the voltage is better. I loaded up one leg with lights, compressor, garage opener, and electric drill, to see what the voltages would do. The one leg draw down was to 112 and the other leg went up to 122. I dont know if this right, but it's a LOT better than before.
Now I got to isolate the neutral in the sub-panel. My neighbor did the hookups, and didn't make it easy to change.
Thanks everyone for your input.
Sam

 

[aandpdan]

DO NOT REMOVE the bonding jumper with a 3 wire sub panel.

2005 NEC 250.32(B)(2).

(2) Grounded Conductor. Where (1) an equipment grounding conductor is not run with the supply to the building or structure, (2) there are no continuous metallic paths bonded to the grounding system in each building or structure involved, and (3) ground-fault protection of equipment has not been installed on the supply side of the feeder(s), the grounded conductor run with the supply to the building or structure shall be connected to the building or structure disconnecting means and to the grounding electrode(s) and
shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded.

The "grounded conductor" is the neutral.

Once you change to 4 wire, remove it.

 

[bentroof]

aandpdan
Thanks for the NEC explaination. Which is what I got going on.
I will leave it bonded for now. It'll work until I get the service upgraded.

Thanks.

 

[wyliesdiesels]

I thought that was changed in 2011. Oh well, will have to look tomorrow. Regardless, the key here is to make sure there is NO other metalic paths between the buildings. If there is, then the bond SHOULD be removed!

 

[Norcal]

I thought that was changed in 2011. Oh well, will have to look tomorrow. Regardless, the key here is to make sure there is NO other metalic paths between the buildings. If there is, then the bond SHOULD be removed!

If there are any metallic paths between the buildings, a 3 wire feed cannot be used but if it is a 3 wire feed the bond must remain, & is only permitted in a existing install.