How Serious is Shared Ground/Neutral

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Old 02-12-19, 11:53 AM
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How Serious is Shared Ground/Neutral

My house was built in 1979 with separate ground and neutral bars in the breaker panel. I didn't understand the significance of this until recently. While I don't understand all the technical aspects, I do now understand how the wires should be routed in a separate system. Almost 10 years ago, I built a small shop and put in 70 amp service from the main service panel. Through my ignorance at the time, I installed a 70 amp panel with combined ground/neutral. Interestingly, the building inspector approved the whole thing without mentioning the difference. My question is whether this is serious enough to warrant replacing the shop panel with one that has separate ground and neutral bars? I do want it to be safe.
 
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Old 02-12-19, 12:45 PM
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If separate structure it was allowed in old codes so inspector may have been right.
Does the cable feeding your shop have 3 wires plus a ground?
 
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Old 02-12-19, 12:46 PM
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At one time is was permitted have ground and neutral combined in a sub panel in a detached building.
I would not be concerned.
 
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Old 02-12-19, 02:07 PM
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If the feeder is 4 wire it's as simple as adding a ground bar to the panel and moving the grounds to it and then removing the grounding strap/screw from the existing bar making it an isolated neutral bar.
 
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Old 02-12-19, 07:08 PM
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It is safe so long as the ground/neutral conductor stays connected.
The concern was if anything happens on that conductor, ground becomes hot, and this can be very dangerous.
I would not be too concerned if it is existing, grandfathered installation. Just inspect and may be re-torque neutral terminal (and also for hot conductors with breaker off).
 
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Old 02-13-19, 08:06 AM
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Thanks for your helpful comments. My shop is an extension of the carport which is, in turn, connected to the house at the roof. So, I guess you could say it is semi-detached. The cable from the main panel to the shop is copper 3-#3 AWG with #10 bare ground. Both the bare ground and the white "neutral" are on the ground bar in the shop panel. Thanks for the comment about adding a separate ground bar. I was wondering if something like that could be done. I'll look into it. The small box is rather crowded, but it may be possible.
 
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Old 02-13-19, 09:44 AM
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You have a four wire feed the neutral and the ground should be isolated.
 
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Old 02-13-19, 12:54 PM
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You have a four wire feed the neutral and the ground should be isolated.
To be more clear, the neutral bar is only to be used for neutrals and should be isolated (not bonded to ground).
 
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Old 02-13-19, 03:15 PM
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Thanks again for the great comments. I've found that ground bars are available from either Lowes or Home Depot for under $10. As soon as I get some other work done, I'll get one and install it.
I appreciate the help and advice.
 
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