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Anonymous Poster

Grounded Neutral

07/07/2009 9:22 AM

I have run in to another instance of the electricial person grounding the neutral to the ground bar and ground rod in a MDB.

This is causing a lot of voltage problems.

When is it ever acceptiable to ground the neutral in a residential MDB?

Thanks
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PWSlack
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#1

Re: Grounded Neutral

07/07/2009 9:24 AM

When the system earthing scheme requires it. Check out the Wikipedia article on earthing systems for more information.

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perry
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#2

Re: Grounded Neutral

07/07/2009 9:59 AM

guest; in the USA the NEC requires the main service neutral to be grounded to ground rods, or copper underground water supply. perry
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EElectrician
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#3

Re: Grounded Neutral

07/07/2009 10:48 AM

In the US, as a general rule, the primary side first electrical disconnecting means after a transformer (or electrical source) should have its neutral bonded to ground. In a distribution panel this is usually accomplished by driving a green hex-head screw through the neutral bar and into the case of the panel. This can also be accomplished by installing a properly sized conductor between the neutral and ground bars.

Note: In some parts of the US the neutral-earth bond is required to be done in the meter base. If the neutral is bonded in the meter base, then it must not be bonded again in the panel or disconnect.

Electrical sub-panels (panels fed from another panel or disconnect rather than from a primary source) should not be bonded to ground. So if an off-the-shelf distribution panel is to be used as a sub-panel , then the green bonding screw is not supposed to be installed, and the neutral bar must be insulated from the housing of the electrical enclosure.

Here's a good website for more information:

http://ecmweb.com/nec/code_top50nec_092506/

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farang1
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#4
In reply to #3

Re: Grounded Neutral

07/07/2009 5:00 PM

Hi,

The electrical guy connected the ire from the ground rod to the ground bar and a jumper to the neutral bar. Here the power company often looses the neutral. won't the system use the ground as the neutral if the neutral is missing?

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North of 60
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#6
In reply to #4

Re: Grounded Neutral

07/08/2009 12:03 AM

Yes...

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EElectrician
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#7
In reply to #4

Re: Grounded Neutral

07/08/2009 8:55 AM

A simple Google search for "neutral bonding jumper" will produce over 17,000 websites that will give lots of good reasons for bonding the neutral.

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North of 60
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#5

Re: Grounded Neutral

07/07/2009 11:50 PM

In Canada... Required by code is the following.

  • The consumer service "neutral conductor", the "identified conductor", must terminate in the service entrance equipment on the "neutral bar".
  • A "grounding conductor" must then connect the neutral bar to a "grounding electrode".
  • A "bonding jumper" connects the neutral bar to the service raceway via a grounding bushing.
  • A "bonding conductor" then connects neutral bar to the case of the service equipment. This is the starting point of the "bonding system".

The section of the CEC that contains these requirements is Section 10.

Here is a diagram.

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EElectrician
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#8
In reply to #5

Re: Grounded Neutral

07/08/2009 9:36 AM

Thanks No60,

I'm pretty sure that we have said the same thing, though your post is better illustrated.

Do they not use the "green screw" in Canada? (This would only be provided if the distribution panel has a main breaker in it.)

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North of 60
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#9
In reply to #8

Re: Grounded Neutral

07/08/2009 10:39 PM

Hey there EE...

Yes, we use green screws or straps or jumpers.

Glad you liked the drawing... though for some reason it posted fuzzy.

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