I have a subpanel in the garage that is that is feed by 6-3 se cable. I have 2 hots and a neutral no ground that was installed by PO, was this ever code? Can I add a ground bar to the panel, saperate the grounds and neutrals and drive a ground rod or do I have to run 4wire cable and a ground rod?
? on subpanel that is feed by 6-3 cable
- Thread starter mdale
- Start date
ForceFed70
Well-known member
It's not to today's code. It may have passed code when it was installed way back when.
The proper thing to do would be to run a 4 wire cable.
If existing cable was run though metal conduit, you may be able to use the conduit as your ground conductor.
2 or 3 ground rods and a seperate ground for the shop isn't to code, but it would probably work and depending on how much trouble running a cable would be, I would be tempted to do this myself. It would certainly be better than what you have right now (no ground).
The proper thing to do would be to run a 4 wire cable.
If existing cable was run though metal conduit, you may be able to use the conduit as your ground conductor.
2 or 3 ground rods and a seperate ground for the shop isn't to code, but it would probably work and depending on how much trouble running a cable would be, I would be tempted to do this myself. It would certainly be better than what you have right now (no ground).
ForceFed70
Well-known member
I will have to let the experts answer that question. I am sure there is a reason why code doesn't allow it. I do believe that having a seperate ground for an outbuilding used to be "OK" but code was changed.
I do know that you would need to be very careful about alternate grounding problems/sources. Say for example if you brought in a CAT5 cable for a telephone. You could end up joining the grounds between the 2 buildings with this cable which could cause a bunch of problems. If I had to guess, I'd say that this is why the code was changed.
I do know that you would need to be very careful about alternate grounding problems/sources. Say for example if you brought in a CAT5 cable for a telephone. You could end up joining the grounds between the 2 buildings with this cable which could cause a bunch of problems. If I had to guess, I'd say that this is why the code was changed.
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ForceFed70
Well-known member
Good point. I always tend to assume we are talking about detached garages.
if you only have 3 wires to the panel DO NOT seperate the neutral and ground -you could kill your self or someone else. The main purpose of the ground is to provide a path back to the source so that when you get a short enough current flows to trip the breaker. If you dont have neutral and ground bonded with a 3 wire feed, anything thats 'grounded' will remain energized if you get a short.
some good info here http://ecmweb.com/grounding/electric_grounding_vs_bonding/
some good info here http://ecmweb.com/grounding/electric_grounding_vs_bonding/
theoldwizard1
Well-known member
I'm really not trying to start a ******* match but I think the OP is asking which is better
- Leaving the ground and neutral bonded inside the sub-panel fed by 3 wire
- Separating the ground from the neutral in the sub-panel, adding a new (isolated from the box) neutral bar and then connecting the ground bar to a couple of ground rods.
Of course the best solution is install a new sub-panel with separate ground and neutral bars and a 4 wire feed.
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acer66
Well-known member
If the OP does not want to go all the way it is maybe the best to leave it alone.
Seems it`s legal right now because it`s grandfathered in but if the op works on it needs to brought up to the current code.
Seems it`s legal right now because it`s grandfathered in but if the op works on it needs to brought up to the current code.
It's a detached garage. theoldwizard1 is correct on what I'm asking. It goes from the house to detached garage/metal polebarn constrution with copper individual 6-6-6-8 in conduit to 1st subpanel then to 2nd part of garage and 2nd subpanel with copper 6-6-6 se cable. The only ground rod is at the main panel in the house. From what I understand I need to have ground rods for each subpanel? Here is a crude drawing. Thanks for the help.
Attachments
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MrMark
Well-known member
No question as to which is best. Leave it alone. The ground does not conduct enough electricity to open a breaker. Relying on a ground rod will get someone killed.
This comes up again and again and this is probably the most misunderstood aspect of residential wiring: grounds. The ground rod is NOT to clear faults; rather it is for lighting protection (probably lame) and to reference the neutral to around 0V AC. The ground rod does nothing for safety (other than lightning). There are millions tons of houses that have no ground rods, never had a ground rod, and work pretty well.
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right. And the second option of seperating the ground is very, very dangerous
Thanks, so leave it alone and all will be good, or run new 4 wire cable. Is it worth the time and money to upgrade to 4 wire? And if I do go to 4 wire do I then need to add ground rods and if so do I do it at both sub panels?
theoldwizard1
Well-known member
If it ain't broke ...
MrMark
Well-known member
You said it's in conduit? If it is of course it makes sense to upgrade to a proper setup. I can't believe that the three wire was ever legal. If you have anything metalic between these buildings than you have a very dangerous situation with your current setup. You would need to drive ground rods (6 feet apart unless you live where I do and you only need 1) at a detatched structure, I don't know about adding them for just a subpanel. I don't have to do it here, but there may be some local codes. People get all fired up about ground rods thinking that they do a lot more than they do for safety.
post a picture of the subpanel -lets see if we can figure out how old it is. All things considered it would likely be best to replace the feeder with a 4 wire one. If it was 3 wire to the detached structure thats one thing, but 3 wire between 2 panels in a metal building i dont like it...
Im thinking 4wire is what i'll do. The panel is a newer siemens, looks like the PO replaced an old panel with it but did not upgrade the wiring. What type of cable do I need to ask for? 6ga copper 4wire? Or is AL an option? The 1st subpanel is an old pushmatic so ill upgrade it to a seimens and then run 4wire cable over to the 2nd subpanel at the same time. I'll try to get pics tonight.
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