Building Steel Bond on Single Phase "Sub-panel", with multiple meters

[crazymanmark7584]

We were called to a local fitness gym that has a very old electrical distribution system. There's a lot of old crap in there, but we have a problem with one of the newer panels that feeds treadmills.
The call was that there was 8 machines about a year ago that had the circuit boards blow up. They were subsequently replaced under warranty of the machine manufacturer.
Then about 3 months ago, a large storm came through the area, and a similar problem occurred, this time with 7 circuit boards in the treadmills "blowing up".
Long long story short, the owner seemed to remember that other panels in the building were balanced, eliminating the problem. It kind of makes sense, sort of, in that balancing the loads would make for a cleaner neutral, potentially eliminating any strange spikes or faults on the phases.
The maintenance tech for the building told me before arriving on site that balancing the loads would potentially work, and to try it, and to look for anything else we could find. So, we investigated. Once opening the panel it was realized it was a single phase 200 amp Main lug only panel. Amp prope on the legs showed about 9 amps on one leg and 11 on the other. It was hard to balance this, 1. because it was pretty close to begin with, and 2. people rotate in and out on the machines constantly
Beyond this, the panel is fed separately metered on the outside of the building. The building is old as I mentioned, and instead of tapping this panel from somewhere, they installed a new meter and riser. On the back of the building this meter is located along with an exterior 200 amp main breaker enclosure.
At this breaker, the installer pulled 3x4/0 aluminum feeders and one #4 bare ground through a 2" EMT, through the space to this panel at the front of the building. It is about 150 linear feet total.
There is another #4 bare copper ground from the neutral lug in the breaker enclosure to a ground rod directly underneath the meter and breaker. I did not measure the resistance on the rod. Upon further review, the ground wire was broken to this rod, as it appears it was broken by a lawn mower or weed whacker. We re-spliced it and continued investigating.
The rest of the building is fed with a 3 phase high leg system, with multiple CT meters both inside and out on the pole (3 total). We did not look for building steel and/or cold water bonds on any of the existing distribution equipment. (this includes 3x 400amp 3 phase disconnects and 1 400 amp CT cabinet, among many other things. It is such a mess I could spend hours figuring where it all goes and still not be totally sure what I'm looking at.)

So, the point...Is this existing 200 amp MLO "sub-panel", that is breaker-ed at the back of the building, about 150 feet away, required to be bonded to building steel? Or is the service that feeds it, for that matter? Like I said, it was grounded to a ground rod at the location of the breaker. This panel IS wired like a sub panel, as in grounds and neutrals are separate.
Secondly, if it is required to be bonded to building steel (which I think it should be....), WHERE should/can this bond be located? At the panel 150' away, or should it be as close to this exterior breaker as it can be?
Is a second ground rod advisable, or allowed per NEC, or is it necessary?
I am being told by other electricians this service needs to be bonded to allow for a backup grounded conductor, should the utility neutral fail, OR should the ground rod/conductor fail, which it did since it was broken.

I went ahead and got a piece of #4 bare copper and bonded the neutral bar to building steel at the problem panel. Is this right, wrong, unnecessary, or just plain dumb?

Advice, please!
Thank you in advance.
-Mark

 

[kwired]

We were called to a local fitness gym that has a very old electrical distribution system. There's a lot of old crap in there, but we have a problem with one of the newer panels that feeds treadmills.
The call was that there was 8 machines about a year ago that had the circuit boards blow up. They were subsequently replaced under warranty of the machine manufacturer.
Then about 3 months ago, a large storm came through the area, and a similar problem occurred, this time with 7 circuit boards in the treadmills "blowing up".
Long long story short, the owner seemed to remember that other panels in the building were balanced, eliminating the problem. It kind of makes sense, sort of, in that balancing the loads would make for a cleaner neutral, potentially eliminating any strange spikes or faults on the phases.
The maintenance tech for the building told me before arriving on site that balancing the loads would potentially work, and to try it, and to look for anything else we could find. So, we investigated. Once opening the panel it was realized it was a single phase 200 amp Main lug only panel. Amp prope on the legs showed about 9 amps on one leg and 11 on the other. It was hard to balance this, 1. because it was pretty close to begin with, and 2. people rotate in and out on the machines constantly
Beyond this, the panel is fed separately metered on the outside of the building. The building is old as I mentioned, and instead of tapping this panel from somewhere, they installed a new meter and riser. On the back of the building this meter is located along with an exterior 200 amp main breaker enclosure.
At this breaker, the installer pulled 3x4/0 aluminum feeders and one #4 bare ground through a 2" EMT, through the space to this panel at the front of the building. It is about 150 linear feet total.
There is another #4 bare copper ground from the neutral lug in the breaker enclosure to a ground rod directly underneath the meter and breaker. I did not measure the resistance on the rod. Upon further review, the ground wire was broken to this rod, as it appears it was broken by a lawn mower or weed whacker. We re-spliced it and continued investigating.
The rest of the building is fed with a 3 phase high leg system, with multiple CT meters both inside and out on the pole (3 total). We did not look for building steel and/or cold water bonds on any of the existing distribution equipment. (this includes 3x 400amp 3 phase disconnects and 1 400 amp CT cabinet, among many other things. It is such a mess I could spend hours figuring where it all goes and still not be totally sure what I'm looking at.)

So, the point...Is this existing 200 amp MLO "sub-panel", that is breaker-ed at the back of the building, about 150 feet away, required to be bonded to building steel? Or is the service that feeds it, for that matter? Like I said, it was grounded to a ground rod at the location of the breaker. This panel IS wired like a sub panel, as in grounds and neutrals are separate.
Secondly, if it is required to be bonded to building steel (which I think it should be....), WHERE should/can this bond be located? At the panel 150' away, or should it be as close to this exterior breaker as it can be?
Is a second ground rod advisable, or allowed per NEC, or is it necessary?
I am being told by other electricians this service needs to be bonded to allow for a backup grounded conductor, should the utility neutral fail, OR should the ground rod/conductor fail, which it did since it was broken.

I went ahead and got a piece of #4 bare copper and bonded the neutral bar to building steel at the problem panel. Is this right, wrong, unnecessary, or just plain dumb?

Advice, please!
Thank you in advance.
-Mark

By bonding the neutral of this "sub panel" to building steel, you have just placed the building steel in parallel with the neutral, and you will have neutral current flowing on the building steel.

From what you describe you likely do have a mess back at the service end of things but the feeder and sub panel sounds like they are done correctly for the most part.

Grounding electrodes need to be run to the service equipment not to load side of service equipment - which your panel you are describing is not service equipment.

If this building steel is not a qualifying grounding electrode it doesn't need a grounding electrode conductor run to it, but it could still be connected to the equipment grounding conductor of equipment that may be likely to energize it, but should never be connected to the grounded service conductor(or neutral) on the load side of service equipment.

 

[kwired]

I am being told by other electricians this service needs to be bonded to allow for a backup grounded conductor, should the utility neutral fail

Far from the truth.

Drive all the ground rods you want, they will never replace a lost neutral.

Grounding electrodes are for bleeding off transients and stabilizing voltage to ground, they are not backups to current carrying conductors, they are not for carrying fault current. This does not mean they will never perform these functions, they just are not intended to perform these functions.

 

[crazymanmark7584]

The saga continues...

The saga continues...

I agree. I don't think it should be another electrician's problem to add another ground rod to an installation that was for the most part right in the first place, and to add another one-it's kind of pointless.
The more I thought about it, the more I also wonder why it is necessary to worry about the utility's neutral being lost...That could happen anywhere on any utility pole or transformer. There will most likely still be high voltage potential between the A and B phases.
And back to my original issue: I'm also going with the notion that this neutral does not have to be bonded to building steel because it is not a separately derived system. Any thoughts on that?

 

[Smart $]

I agree. I don't think it should be another electrician's problem to add another ground rod to an installation that was for the most part right in the first place, and to add another one-it's kind of pointless.
The more I thought about it, the more I also wonder why it is necessary to worry about the utility's neutral being lost...That could happen anywhere on any utility pole or transformer. There will most likely still be high voltage potential between the A and B phases.
And back to my original issue: I'm also going with the notion that this neutral does not have to be bonded to building steel because it is not a separately derived system. Any thoughts on that?

The outside panel is service equipment containing the service disconnect. As such, it is subject to all the GES and bonding rules of Article 250. Using structural steel as an electrode is only required if it qualifies as such... and that may be next to impossible to verify in an existing building. Bonding is another matter, but I wouldn't hesitate to bond it.

 

[kwired]

but I wouldn't hesitate to bond it.

But not to a load side of service equipment grounded (neutral) conductor - right?

 

[Smart $]

But not to a load side of service equipment grounded (neutral) conductor - right?

Correct. I was discussing grounding and bonding at the outside panel, in which is the service disconnect.

 

[augie47]

...............................

There is another #4 bare copper ground from the neutral lug in the breaker enclosure to a ground rod directly underneath the meter and breaker. I did not measure the resistance on the rod. Upon further review, the ground wire was broken to this rod, as it appears it was broken by a lawn mower or weed whacker. We re-spliced it and continued investigating.

By Code you can not splice a grounding electrode conductor except by listed irreversible means ({250.64(C)}

The rest of the building is fed with a 3 phase high leg system, with multiple CT meters both inside and out on the pole (3 total). We did not look for building steel and/or cold water bonds on any of the existing distribution equipment. (this includes 3x 400amp 3 phase disconnects and 1 400 amp CT cabinet, among many other things. It is such a mess I could spend hours figuring where it all goes and still not be totally sure what I'm looking at.)

So, the point...Is this existing 200 amp MLO "sub-panel", that is breaker-ed at the back of the building, about 150 feet away, required to be bonded to building steel? Or is the service that feeds it, for that matter?

As noted by others, in general, all grounding electrode connections are made at the service. All grounding electrodes at the premises should be used. The structural steel would normally be bonded at the service either because it is an electrode or because it is required to be bonded in general

Like I said, it was grounded to a ground rod at the location of the breaker. This panel IS wired like a sub panel, as in grounds and neutrals are separate.
Secondly, if it is required to be bonded to building steel (which I think it should be....), WHERE should/can this bond be located? At the panel 150' away, or should it be as close to this exterior breaker as it can be?

Again,at the service.

Is a second ground rod advisable, or allowed per NEC, or is it necessary?

May not be necessary (see 250.56), but certainly allowed

I am being told by other electricians this service needs to be bonded to allow for a backup grounded conductor, should the utility neutral fail, OR should the ground rod/conductor fail, which it did since it was broken.

Sound like folks that may not be your best advisers

I went ahead and got a piece of #4 bare copper and bonded the neutral bar to building steel at the problem panel. Is this right, wrong, unnecessary, or just plain dumb?

Advice, please!
Thank you in advance.
-Mark

Wrong. As noted, the grounded (neutral) should only be bonded to grounding means at the service.