Residential service with two panels - separated neutrals/grounds in each panel?
Residential service with two panels - separated neutrals/grounds in each panel?
(OP)
A homeowner has a 300A service that comes into a meter base on one end of his house and it splits off to two separate panels, one in his main house about 50'away and the other to another panel in a detached garage about 75' away. The ground rod is located at the meter base. They used a service type panel with neutral bars along the sides and all the neutrals and grounds are on the same bars.
It was recently inspected and he was told that in the house panel that the equipment grounds and the neutrals are insufficiently separated.
We are trying to figure out what he is talking about. My theory is is that the ground and neutral is bonded at the meter base and therefore can't be tied together again. Any ideas? And is there an easy fix?
It was recently inspected and he was told that in the house panel that the equipment grounds and the neutrals are insufficiently separated.
We are trying to figure out what he is talking about. My theory is is that the ground and neutral is bonded at the meter base and therefore can't be tied together again. Any ideas? And is there an easy fix?






RE: Residential service with two panels - separated neutrals/grounds in each panel?
RE: Residential service with two panels - separated neutrals/grounds in each panel?
If there are two neutral buses you may be able to remove the connection between them and use one for a ground bus. Check with the AHJ before making any changes.
Panels with common ground and neutral bus are common in some countries in Central America.
Bill
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"Why not the best?"
Jimmy Carter
RE: Residential service with two panels - separated neutrals/grounds in each panel?
Looking at the circuit the neutral in between the main and the first panel would be carrying ground current in the case of a fault. But I'm thinking that's what the Utility does..., they don't have a seperate ground wire. So what's the hazard?
That's good advice to talk to AHJ first before making changes. This house passed electrical inspection.
As a fix I was thinking we would have to buy a seperate ground bus with a big lug on it to connect a seperately pulled in wire. Then re-wire all the grounds from the branch circuits to this bus.
RE: Residential service with two panels - separated neutrals/grounds in each panel?
RE: Residential service with two panels - separated neutrals/grounds in each panel?
Current comes in on L1 or L2 and goes out on the neutral.
Great. The ground conductor is there as an emergency path for a wayward L1 or L2 that gets shorted to something metal. Not the normal return current.
The problem with connecting the ground to the neutral again at the 2nd or 3rd panels is that everyday return current will flow through both the ground wire and neutral wire. So what? Remember that everything metal that is "safety grounded" is now hooked to a midpoint neutral connection that by the very nature of ohms law will become energized (compared to the pole ground)as load current increases. Tingling (shock) is the result. And worse yet, a line to neutral fault causes the voltage from the safe ground conductor to rise further above earth potential. This results in what is known as step and touch potential that can kill.
99% of electrical panels have seperate neutral and ground busses. Typically the ground busses are fastened to the metal box, and the neutral bus is insulated from the metal box. Suppliers put a jumper between the two, so that you can bond them ONCE at the service entrance. Otherwise the jumper is removed for subpanels.
For further reading search for a whitepaper called "Grounding: the Good, the Bad, and the Stupid"
Donald Zipse
Electrical Forensics, LLC
and "Death by Grounding" by the same author.
RE: Residential service with two panels - separated neutrals/grounds in each panel?
RE: Residential service with two panels - separated neutrals/grounds in each panel?
RE: Residential service with two panels - separated neutrals/grounds in each panel?
See Article 250.32 in the NEC. You probably need a grounding electrode at each of the panels if these are in separate buildings or structures.
When it comes to NEC compliance, you really cannot use common sense, engineering judgement or laws of nature - you just have to do what the NEC says (or what the local AHJ thinks it says).
RE: Residential service with two panels - separated neutrals/grounds in each panel?
The outbuilding panel does have another ground rod. BTW at the outbuilding we are NOT to tie the neutral and ground together there either right? Just this additional ground rod?
RE: Residential service with two panels - separated neutrals/grounds in each panel?
RE: Residential service with two panels - separated neutrals/grounds in each panel?
If we can fairly easily correct to meet Code...we'll do it, everyone will be happy, and the new Owner won't have to bother with it if he sells the house. A ground bus bar for this panel is about $7 dollars at Home Depot.
RE: Residential service with two panels - separated neutrals/grounds in each panel?
RE: Residential service with two panels - separated neutrals/grounds in each panel?
And I did talk to the County Building Inspector, and he without looking at it, said he understood what I was talking about and agreed and would probably go along with not doing anything. After all they did sign off on the installation before. But we don't want to not have it at present Code cause who knows who may say something different in the future.
RE: Residential service with two panels - separated neutrals/grounds in each panel?
RE: Residential service with two panels - separated neutrals/grounds in each panel?
No offence but - if you don't understand about separation of neutrals and grounds, and when to and when not to, and how to and how not to, you are probably not qualified to do it, or even to assist. I would consult a qualified electrician and in that manner you can be of help.
That being said - the neutral and the ground are identical up to and including the panel that has the MAIN SERVICE DISCONNECT. Any panel downstream from the main panel must have an extra (grounding) conductor as part of the feeder and all neutrals and grounds at the downstream panel(s) must be kept entirely separate from one another.
Again - if you are not sure you can really hurt someone. Mistakes in this area are rather common. If you need help at least consult with the inspector who is telling you that it is incorrect, make a call, stop in his office.
RE: Residential service with two panels - separated neutrals/grounds in each panel?
Bill
--------------------
"Why not the best?"
Jimmy Carter