Main Disconnect w/o MBJ

TwoBlocked

TwoBlocked

Senior Member
Location
Bradford County, PA
Occupation
Industrial Electrician
Here's some pictures. The Disc if right next to the meter box. The breaker Panel is around 200' away. The neutral and ground are separate in the breaker panel. My thought is to use polaris connectors. Other ideas?
 
No fuses? This doesn't seem like the service disconnect with no overcurrent protection. Is it a utility required meter disconnect? Can the breaker panel be the service disconnect and you bond there?
 
Little Bill said:
Not sure what you are asking?
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Am asking how others would install the required MBJ.
jaggedben said:
No fuses? This doesn't seem like the service disconnect with no overcurrent protection. Is it a utility required meter disconnect? Can the breaker panel be the service disconnect and you bond there?
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I don't believe the Main Service Disconnect requires to also be a OCPD. And I worry about fuses with a split phase system. If just one leg blows, you can get feedback through a 240V device and un balanced voltages in the system to single leg devices.
infinity said:
And why a switched neutral?
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One possibility is a three pole disconnect is what was available and was also a convenient place for landing the neutrals.
ramsy said:
Are corner grounded-deltas allowed to switch the neutral, relying on bonded disconnect to meter?
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This is a split-phase system.
 
This is at a gas compression site. Out here, the industry is still a bit like the Wild West. I measured 7 ohms between the neutral and ground at the breaker panel. Didn't give me a warm and fuzzy feeling.
 
TwoBlocked said:
I don't believe the Main Service Disconnect requires to also be a OCPD. And I worry about fuses with a split phase system. If just one leg blows, you can get feedback through a 240V device and un balanced voltages in the system to single leg devices.
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230.91 requires the overload protection to be integral to the service disconnect or immediately adjacent, which you evidently don't have here. I agree that you don't want a fuse in the neutral but otherwise feedback doesn't damage anything, you can get phantom voltages but they basically can't deliver power.

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Am asking how others would install the required MBJ.
Click to expand...

Does this need to be by the book or do you just want to make it safe? If the latter, I think I would declare it my understanding that the disconnect you show is a meter disconnect and not the service disconnect, and I'd put my MBJ in at the breaker you described 200' downstream. Then the green wires in you photo presumably become SSBJs and the meter disco in the photo is also bonded. Don't do a second bond in the meter disco because it would create an unnecessary parallel path.
 
jaggedben said:
230.91 requires the overload protection to be integral to the service disconnect or immediately adjacent, which you evidently don't have here. I agree that you don't want a fuse in the neutral but otherwise feedback doesn't damage anything, you can get phantom voltages but they basically can't deliver power.



Does this need to be by the book or do you just want to make it safe? If the latter, I think I would declare it my understanding that the disconnect you show is a meter disconnect and not the service disconnect, and I'd put my MBJ in at the breaker you described 200' downstream. Then the green wires in you photo presumably become SSBJs and the meter disco in the photo is also bonded. Don't do a second bond in the meter disco because it would create an unnecessary parallel path.
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Thanks, I understand what yo are saying - the only device capable of being the service disconnect, in this case, is the breaker panel. That is the place the MBJ needs to be installed.

Oh, and I wasn't talking about fusing the neutral. I was talking about fusing the ungrounded conductors. Lets way the fuse blows only on leg "B". The fridge happens to be on leg "B" and it isn't running, Until the 240V dryer is started. This back feeds voltage to the "B" leg, creating a voltage divider between the dryer and the fridge. They are both running on reduced voltage and liable to burn up.
 
jaggedben said:
230.91 requires the overload protection to be integral to the service disconnect or immediately adjacent
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Does that also apply to 230.85 outside service-rated Emergency switch, when service OCP is inside, per 230.90?
 
TwoBlocked said:
the only device capable of being the service disconnect, in this case, is the breaker panel. That is the place the MBJ needs to be installed.
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Can MJB be at both meter and breaker panel?

250.184(2)(B)(7)
"The neutral conductor, where provided, shall be insulated and isolated from earth except at one location"
 
Huh! Found what lead me astray, and thanks to everyone for getting back on track. This meter disconnect switch should have been labelled "METER DISCONNECT, NOT SERVIE EQUIPMENT" NEC 2020 230.82 (3). Someone else must have also gotten mislead due to the fact that the breaker box does not have a MBJ.
 
ramsy said:
Can MJB be at both meter and breaker panel?

250.184(2)(B)(7)
"The neutral conductor, where provided, shall be insulated and isolated from earth except at one location"
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250 Part X does not apply here. Both the meter and the breaker panel could be bonded to neutral but then the green wires between the two, shown in his photos, would not be necessary and would arguably violate 250.6.
 
jaggedben said:
250 Part X does not apply here. Both the meter and the breaker panel could be bonded to neutral but then the green wires between the two, shown in his photos, would not be necessary and would arguably violate 250.6.
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Excellent, thanks for the clarification
 
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