Ground and Neutral at panelboard

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AE-29

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While working at a hospital I came across a panelboard that was carring 5 amps on the Ground terminal block. I also noticed a neutral conductor bonded to the ground block. I believe the only time this is permitted is with a high impedance neutral system. This is not the case here.The grounded locknut to the feeder conduit is also strange, 5amps on one side of the clamp and 2 on the other with the screw tightned. Well, I disconnected the neutral and the amps dropped to 3. I checked 5 other similiar panels and they had the same neutral to ground bond. This was how it was originally wired 30 years ago. My question is does this sound strange and should I disconnect the panels with this type of wiring. My feeling is that this is dangerous.
 
I think your right. The neutral and ground busses should be bonded in one and only one place. That is at the the service entrance point. Any downstream connections are dangerous in that they can put neutral current on the equipment grounding conductor and any metal parts of equipment that is bonded to the EGC.
 
AE-29 said:
correction to the voltage... 480 from the switchbd to xfmr 208/120 feeding neutral connected loads.
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good catch, don


AE, if you are speaking of the 208Y/120 boards, I'm fairly certain you are dealing with an installation that was acceptable 30 years ago. I don't believ the "redundant path" wasn't addressed by the Code until the last few cycles.
 
Is the panel in question the first panel downstream of a transformer?

Roger
 
Hello Don,

don_resqcapt19 said:
Roger,

That is exactly where all of my questions are leading.
Don
Click to expand...

I thought so. :)

Roger
 
Ok my understanding is at the transformer the neutral bonded to the GROUND is acceptable since it essentially becomes a new service point. But even, at the first panebd I disagree that bonding to the EGC is ok. Now, maybe 1 panelbd, but not 3 bds coming from the same xfrmr. I thought if I were to connect a gfci to this PBd it would trip but unknown to me why, it didn't. I removed this bond and observed a spark as I placed it back. Current is obviously flowing to the EGC. My latest reading on the ground bus is 10 amps. I've been told it's been working for 30 years.
 
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AE-29 said:
Ok my understanding is at the transformer the neutral bonded to the GROUND is acceptable since it essentially becomes a new service point.
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It's required to be at either (can be both with no parallel paths) the Transformer or the Panel BUT, it should not be at the Panel and the Transformer if there are any common metalic paths to both. (which I'm sure there is)

Is the bonding taking place at both locations?


Roger
 
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I'm not an expert on grounding/bonding, and I've never worked with these voltages, but doesn't a continuous load on the ground and the type of multiple bonding jumpers described equal a very dangerous ground loop condition?

No matter how long it's been working or what the code said 30 years ago, dangerous is dangerous - there are reasons the code has changed - I would address this issue immediately, get someone who knows these systems out there asap.
 
but doesn't a continuous load on the ground and the type of multiple bonding jumpers described equal a very dangerous ground loop condition?
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"Very dangerous", probably not.
No matter how long it's been working or what the code said 30 years ago, dangerous is dangerous - there are reasons the code has changed
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Don
The code hasn't really changed in this area.
Don
 
Don

Don

.
Maybe Im not reading you correctly. Your admonition on not bonding both ends from Xfmr to first panel is correct and was adressed in a not so recent code cycle. Parallel grounding or parallel neutral conductors, take your pick.

Current on a EGC is not meant to be under normal load.

Yes I know it isnt very dangerous as desribed in this particular OP.

As electricians we no longer run a EGC along with a GC from Xfmr to any MDP.
Under/as the desribed OP conditions.

Inspectors in my area wont allow it. So how and why hasnt things changed?

Code wise that is.
 
gmack,
As electricians we no longer run a EGC along with a GC from Xfmr to any MDP.
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Then how is the case of the transformer connected to a fault clearing path. An EGC is required.
Don
 
gmack,
So how and why hasnt things changed?
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What code change are you talking about? My codes only go back to 78, but even then you could only make the grounding connection at a single point. The only real difference is that you were required to make that connection at the transfomer, not at either the transformer or first disconnect as now permitted.
Don
 
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