3-Wire Sub-panel

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Jazzman

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My barn/shop was wired in the 1990’s and has 3 wires coming from the main panel at the house(2 hots and 1 neutral). I know that is not up to current code but I’m wondering if it’s still safe to use for my woodworking machines. There is 1 ground rod in ground but I think they now require 2. Would just running a ground wire from main panel do the trick? Is that really necessary? Any thoughts or recommendations?

Thanks!
 

Jadnashua

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Personally, I'd drive at least another ground stake in. That really depends on your soil conditions and the amount of rainfall.

FWIW, if you use GFCI protections, those don't even require a ground to provide extra safety...they only look at the power in/out and compare the two...if they're not even, it trips. The implication is that if they aren't equal, some of that energy went to ground, which is a fault, thus the name of the device. That energy may be going through you, and that's the safety issue. Many of today's smaller hand tools are double-insulated, and may not have a ground lead on the cord at all.

If your tools are 120vac, I'd add GFCI and carry on. They do make 240-vac GFCI breakers and probably sockets, too.

The house I grew up in had no grounded receptacles. I wasn't up to rewiring the whole house, and put in a bunch of GFCI receptacles, and grounded ones downstream to make it a bit safer (that's allowed if you put a sticker on each one indicated there's no ground and it's protected via GFCI).
 

wwhitney

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My barn/shop was wired in the 1990’s and has 3 wires coming from the main panel at the house(2 hots and 1 neutral). I know that is not up to current code but I’m wondering if it’s still safe to use for my woodworking machines. There is 1 ground rod in ground but I think they now require 2. Would just running a ground wire from main panel do the trick? Is that really necessary? Any thoughts or recommendations?
If your shop and your house are two separate buildings, and the only electrically conductive path between them is the ungrounded feeder, then your ungrounded feeder is OK to continue using. If you have a communications cable (phone, TV, network) or a metallic water line or anything like that connecting them, then you need to install a modern feeder with grounding conductor.

In either case, you need a grounding electrode system at your barn, which if it is only ground rods needs to be 2 grounds rods. But if you have a concrete encased electrode (UFER) that would suffice. You need a main disconnect at the point the feeder enters the building. If the feeder is ungrounded, then your barn EGC system starts there, and you bond together your barn EGCs, the grounding electrode system, and the feeder neutral. Whereas if your feeder has a grounding conductor, then you tie together your barn EGCs and the grounding electrode system with the feeder EGC, and none of those connect to the feeder neutral.

Very important and so worth repeating: if you have an ungrounded feeder, then your ground and neutral in the barn need to be bonded together at the main disconnect. Otherwise a hot to EGC short will not trip a breaker.

Cheers, Wayne
 

Jazzman

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Personally, I'd drive at least another ground stake in. That really depends on your soil conditions and the amount of rainfall.

FWIW, if you use GFCI protections, those don't even require a ground to provide extra safety...they only look at the power in/out and compare the two...if they're not even, it trips. The implication is that if they aren't equal, some of that energy went to ground, which is a fault, thus the name of the device. That energy may be going through you, and that's the safety issue. Many of today's smaller hand tools are double-insulated, and may not have a ground lead on the cord at all.

If your tools are 120vac, I'd add GFCI and carry on. They do make 240-vac GFCI breakers and probably sockets, too.

The house I grew up in had no grounded receptacles. I wasn't up to rewiring the whole house, and put in a bunch of GFCI receptacles, and grounded ones downstream to make it a bit safer (that's allowed if you put a sticker on each one indicated there's no ground and it's protected via GFCI).

Hey, thanks for your input! It’s worth a lot. If I add a second ground rod it would have to be horizontally installed because of soil conditions. It looks like that’s ok as long as it’s installed 30” deep and 6’ from 1st ground rod. The tools I’m about to hook up are both 240 volts. Would changing out 60 amp sub panel breaker with 60 amp gfci breaker add a level of protection? Or would all individual breakers need to be gfci?

Thanks!
 

Jazzman

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If your shop and your house are two separate buildings, and the only electrically conductive path between them is the ungrounded feeder, then your ungrounded feeder is OK to continue using. If you have a communications cable (phone, TV, network) or a metallic water line or anything like that connecting them, then you need to install a modern feeder with grounding conductor.

In either case, you need a grounding electrode system at your barn, which if it is only ground rods needs to be 2 grounds rods. But if you have a concrete encased electrode (UFER) that would suffice. You need a main disconnect at the point the feeder enters the building. If the feeder is ungrounded, then your barn EGC system starts there, and you bond together your barn EGCs, the grounding electrode system, and the feeder neutral. Whereas if your feeder has a grounding conductor, then you tie together your barn EGCs and the grounding electrode system with the feeder EGC, and none of those connect to the feeder neutral.

Very important and so worth repeating: if you have an ungrounded feeder, then your ground and neutral in the barn need to be bonded together at the main disconnect. Otherwise a hot to EGC short will not trip a breaker.

Cheers, Wayne
If your shop and your house are two separate buildings, and the only electrically conductive path between them is the ungrounded feeder, then your ungrounded feeder is OK to continue using. If you have a communications cable (phone, TV, network) or a metallic water line or anything like that connecting them, then you need to install a modern feeder with grounding conductor.

In either case, you need a grounding electrode system at your barn, which if it is only ground rods needs to be 2 grounds rods. But if you have a concrete encased electrode (UFER) that would suffice. You need a main disconnect at the point the feeder enters the building. If the feeder is ungrounded, then your barn EGC system starts there, and you bond together your barn EGCs, the grounding electrode system, and the feeder neutral. Whereas if your feeder has a grounding conductor, then you tie together your barn EGCs and the grounding electrode system with the feeder EGC, and none of those connect to the feeder neutral.

Very important and so worth repeating: if you have an ungrounded feeder, then your ground and neutral in the barn need to be bonded together at the main disconnect. Otherwise a hot to EGC short will not trip a breaker.

Cheers, Wayne

Hi Wayne,

I will check sub panel to see if neutral and grounds are bonded to panel. If not, I will add bonding screws. I do know there are no other cables or metallic pipes between barn and house.

Thank you!
 

Jadnashua

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They do make 240vac GFCI breakers...that alone should make things safer. Having a solid ground connection gives an alternate path to trip a standard fuse or breaker, but never should have any current on it when things are working properly. In a way, a GFCI provides an alternate way to trip the circuit if there's a fault - overcurrent still works if there's a direct short to ground, if ground is solid. A short to ground, if it doesn't allow conduction, is useless.

The soil conditions will determine how good the ground point actually is. Way back when at Ft Bliss in TX, I was talking to the colonel that ran the unit that dealt with communications where ground is critical for things like an antenna array and phone systems to work properly. He said because of the sand and dryness, a month or so before they were going to do a field exercise, he'd have the cooks order lots of extra salt. Then, they'd mix up a brine and pour it on the ground before setting up their grounds. That was the only way to get a clean radio and phone signal and keep the generators safe. Not exactly environmentally a great solution, but necessary. IOW, getting a good ground connection can be tricky. Using two rods gives a little redundancy and helps to ensure it's safer.
 

wwhitney

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The grounding electrode system is not part of the primary safety system for 120V - 480V systems. Its safety purpose is for lightning strikes (maybe) and the case of primary (high voltage) lines falling on secondary lines.

Cheers, Wayne
 
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