Proper securing of bonding jumper?

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epilarz

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Hello, Does anyone know of a NEC rule pertaining to the securing of a bonding jumper? My specific question is in regard to the use of a two screw non-metalic cable clamp being required to secure a 4/0 bonding jumper as it entered the side-wall of a UPS cabinet. The bare bonding jumper ran about 6 feet on a cinderblock wall. It started at a grounding bar in the room, then was strapped to the wall about every 12" along it's length until it penetrated the sidewall of the UPS unit where it was terminated on an appropriate size lug. I am aware of the requirement of the need to bond the grounding electrode conductor if run in a metalic conduit. In this installation the 4/0 was passing thru an existing hole in the side of the unit. I was told that the clamp was needed at the side-wall of the unit to prevent arcing if a fault condition were to happen? When you run a grounding electrode conductor lets say on a 200 amp residential service the manufacturer supplies you with a knock out for the GEC and no clamp is required in that situation, I don't see any difference? If I am wrong could someone kindly correct me!

Thanks much, Ed P.
 
If the UPS manufacturer specifically calls out in their instructions a standard NM strap fitting as a clamp/bonding means, then I could reasonably assume they obtained their NRTL listing with it (i.e. evaluated it). However, if the installer is making this decision, I would contend that the fitting is not being used in the purpose for which it designed - therefore the listing is not valid.

With that being said...Most (if not all) NM metallic strap clamps are designed for 14/2 NM minimum - not a single 4/0. If the 4/0 lands on a lug inside the UPS equipment, then I don't see any issue. However, if it *IS* the sole connection to the enclosure, the fitting would need to be tested for that purpose.
 
erickench said:
Are you installing a bonding jumper or a grounding electrode conductor? Because that's two different things.
Click to expand...

Sorry, Typing too fast and not thinking!

This would be a Grounding Electrode Conductor going from a grounding bar to a grounding lug inside the UPS cabinet.

Thanks! Ed P.
 
LJSMITH1 said:
If the UPS manufacturer specifically calls out in their instructions a standard NM strap fitting as a clamp/bonding means, then I could reasonably assume they obtained their NRTL listing with it (i.e. evaluated it). However, if the installer is making this decision, I would contend that the fitting is not being used in the purpose for which it designed - therefore the listing is not valid.

With that being said...Most (if not all) NM metallic strap clamps are designed for 14/2 NM minimum - not a single 4/0. If the 4/0 lands on a lug inside the UPS equipment, then I don't see any issue. However, if it *IS* the sole connection to the enclosure, the fitting would need to be tested for that purpose.
Click to expand...

Sorry I was not more specific, I had completed the installation, then a couple of hours later had to re-work the installation to include the two-screw n/m clamp being told (by co-worker, not inspector) the way I ran the cable thru a hole in the side of the cabinet was a code violation. I have installed many pieces of equipment in the past (transformers/switchgear etc.) with no connector/clamp of any kind on the GEC where it enters the inclosure and don't see it as a violation.

Thanks again for your time and input! Ed P.
 
And what does a fault condition have to do with a grounding electrode circuit?
The grounding electrode is there in case lightning strikes the system. In an ungrounded system(or unbonded) the GEC would have no direct connection to the neutral. It would have to be connected to the enclosure itself.
 
erickench said:
And what does a fault condition have to do with a grounding electrode circuit?
The grounding electrode is there in case lightning strikes the system. In an ungrounded system(or unbonded) the GEC would have no direct connection to the neutral. It would have to be connected to the enclosure itself.
Click to expand...

I would rethink that, A UPS is a separately derived system, and must follow the rules in 250.30

The EGC, GEC, and neutral must be bonded together.
 
hurk27 said:
I would rethink that, A UPS is a separately derived system, and must follow the rules in 250.30

The EGC, GEC, and neutral must be bonded together.
Click to expand...

NEC 250.30(B) outlines the rules for ungrounded separately derived systems. It's permitted to have one. NEC 250.30(B)(1) state's that the grounding electrode conductor shall be used to connect the metal enclosure to the grounding electrode.
 
erickench said:
NEC 250.30(B) outlines the rules for ungrounded separately derived systems. It's permitted to have one. NEC 250.30(B)(1) state's that the grounding electrode conductor shall be used to connect the metal enclosure to the grounding electrode.
Click to expand...

In an ungrounded system(or unbonded) the GEC would have no direct connection to the neutral
Click to expand...
1. If it was an ungrounded system there would be no neutral, only deltas are allowed to be ungrounded.
see 250.20(B)

2. I have never heard of an ungrounded UPS system myself, I know of a few ungrounded generators systems that transfer into a ungrounded delta, But never a UPS. I'm not saying there is no ungrounded delta UPS system out there, just never heard of one.:confused:
Most are 3 phase Y or single phase see 1. above

I was just confused because I'm sure the OP was talking about a grounded system, because of the UPS?
 
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My thoughts exactly. This is a big UPS system for Ford MO.Co. 480 volt ungrounded system. The GEC connecting from ground lug-to-ground bar with no connection to neutral because there isn't one in this UPS.

Thanks again guys! Ed P.
 
I would just use one of these:

kennyclamp.jpg


This is a Kenny Clamp which is designed to connect GEC's to enclosures. In your case you would need to reduce the GEC to #3/0. That's the largest size required by 250.66 and largest size that this clamps will handle.
 
Hi Rob, Thanks for the neat connector info. That would be exactly what was needed if the manufacturer had not supplied a connection point inside their equipment with specific instructions to connect the GEC to a particular lug. What I had issue with is that I was being told that a two-screw n/m cable connector was serving the same function as a bonding clamp at the end(or ends) of a conduit when you run the GEC through a metallic piece of conduit. In my situation the GEC passing through a 7/8" hole in the thin sheet metal cabinet would not have the same effect.

Thanks again for everyone's help and input! Ed P.
 
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