MBJ for old Challenger Panel

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Jerramundi

Jerramundi

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Chicago
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Licensed Residential Electrician
I've been asked by an inspector to upgrade the grounding and bonding for a couple old Challenger panels on a job in which I had nothing to do with the panels *sigh* and I just wanted to get some feedback on how I plan to install my MBJ.

The neutral bus is isolated from the enclosure. The plan is to run a #6 MBJ from the neutral bus, continuously through a newly installed ground bar, to a bonding bushing on the service entrance raceway... in order to connect the EGCs (ground bar) and enclosure (bonding bushing) to the grounded conductor.

I'm used to the pretty green screw on new Siemens panels so I just wanted to make sure this method is acceptable and well, practical. Any input would be greatly appreciated.
 
Duplicate?

MBJ and GEC for Multiple Main Breaker Panels

Hey all. Trying to help a friend out who just bought a building and really not used to the grounding and bonding of multiple main breaker panels. Single main breaker panel I got. Single main breaker panel and sub panel(s) I got. Multiple main breaker panels are not really something I deal with...
forums.mikeholt.com

I said the MBJ looked ok. I am not always right, but one thing that is more certain than death and taxes is that if you say something wrong on this forum, someone will correct you 🧐 :LOL: The bonding jumper to the bonding bushing does not need to be continuous with the MBJ. Make sure those panels are suitable for use as service equipment.
 
electrofelon said:
Duplicate?

MBJ and GEC for Multiple Main Breaker Panels

Hey all. Trying to help a friend out who just bought a building and really not used to the grounding and bonding of multiple main breaker panels. Single main breaker panel I got. Single main breaker panel and sub panel(s) I got. Multiple main breaker panels are not really something I deal with...
forums.mikeholt.com

I said the MBJ looked ok. I am not always right, but one thing that is more certain than death and taxes is that if you say something wrong on this forum, someone will correct you 🧐 :LOL: The bonding jumper to the bonding bushing does not need to be continuous with the MBJ. Make sure those panels are suitable for use as service equipment.
Click to expand...

Slight duplicate *shifty eyes* haha. In the previous post, I was more so inquiring about the sizing of the MBJ. I'm clear on that now. In this post I'm inquiring about the installation method itself.

This is where I get a little confused without that nice, shiny green screw. Doesn't the definition of the MBJ require it to be continuous (i.e. "unspliced) through three items: (1) the ungrounded conductor, (2) the egcs, and (3) the enclosure?

Most of the graphics in the handbook depict (2) jumpers: (1) MBJ from neutral bus / grounded conductor to enclosure... and (2) SSBJ from neutral bus to bonding bushing on service entrance raceway... but I don't see how this type of MBJ covers all three of the aforementioned bonding points, unless you count bonding the MBJ to the enclosure as a means of connection to the EGC bus bar, which is also bonded to the enclosure.

Typically I land the GEC on the neutral bus, run a bonding jumper from a bonding bushing on the service entrance raceway to the neutral bus, tighten that green screw, and land my EGCs on a separate EGC bus bar... but it's just muscle memory from habit. I'm trying to comprehend it on an intellectual level now so I can apply it to varying circumstances, like the one I'm currently facing.
 
suemarkp said:
Is this a 200A panel? If so, I think you need #4 and not #6.
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Not a 200A panel. One set of 200A AWG Overhead Service Conductors feeding a single, triple Meter bank, which feeds 3 separate 100A Main Breaker panels. MBJ is sized according the ungrounded conductors in each individual panel.

I actually think I can use a #8 according 250.102(C)(1) since the ungrounded conductors in each panel are #1 aluminum (yes, I know they should be copper, but they are existing). However, the inspector asked for a #6 so I'm just doing it. I'm too tired for a debate that would save a couple cents per foot in wire, haha. It's a "pick your battles wisely" kinda thing ;)
 
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Jerramundi said:
3 individual Main Breaker Panels, all listed for such.
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Then, yes, there should be a jumper (screw or conductor) bonding the EGCs and the enclosure to the neutral.

Yes, the electrodes should land on the neutral bus, but each unspliced jumper can be a separate conductor.
 
LarryFine said:
Then, yes, there should be a jumper (screw or conductor) bonding the EGCs and the enclosure to the neutral.
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That much I got... that all 3 items need to be bonded together by the MBJ. My question is more about the "how."
I hear "unspliced" and see one continuous jumper/wire connecting all 3 items...
 
Jerramundi said:
That much I got... that all 3 items need to be bonded together by the MBJ. My question is more about the "how."
I hear "unspliced" and see one continuous jumper/wire connecting all 3 items...
Click to expand...
No, that refers to the electrode conductor(s) specifically.
 
LarryFine said:
No, that refers to the electrode conductor(s) specifically.
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How does that refer to the GEC's?

250.24(B) Main Bonding Jumper. For a grounded system, an unspliced main bonding jumper shall be used to connect (1) the equipment grounding conductor(s) and (2) the service-disconnect enclosure to the (3) grounded conductor within the enclosure for each service disconnect in accordance with 250.28.

250.24(A)(4) Main Bonding Jumper as Wire OR Busbar. Where the main bonding jumper specified in 250.28 is a wire or busbar....

The logical operand "OR," in my mind, makes the use of wire OR busbar mutually exclusive.

In other words, choose one or the other. That you cannot utilize separate pieces of jumper wires joined by a busbar to accomplish the bonding of all 3 aforementioned items.

This is why I'm asking if a single piece of wire run from the neutral bus, continuously through a newly installed EGC bar, to a bonding bushing on the service entrance raceway sounds right.
 
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Why do you have a separate EGC bar? You can use the neutral bar for grounding unless you don't have enough terminals, which is common in older panels.
 
suemarkp said:
Why do you have a separate EGC bar? You can use the neutral bar for grounding unless you don't have enough terminals, which is common in older panels.
Click to expand...
Given that these are all main breaker panels, yes... I could land the EGCs on the neutral buses. I'm considering doing this on 1 out of the 3 panels because it is relatively newer with a good number of positions available. The other 2 panels are old Challenger panels and lack of terminals is precisely the problem. Also, kind of a personal preference. Looks cleaner, IMO
 
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