This is how I understand a res service is done. If the MBJ in the main panel is removed, I’d have to isolate grounds and neutrals correct?

[ActionDave]

SomeRandomPerson welcome to the forum. Your thread has come at a time that coincides with a major code change that has a lot of us confused, not just the green apprentices.

Under 2020 code you are allowed what amounts to a "Main Bonding Jumper" in two locations, one outside the house and one inside the house. This was never allowed for the last seventy some years, so a lot of us are trying to work out what this means. I hope you hang in there with the discussion as it evolves and don't get frustrated. Both the old dogs and the new are going to learn something.

 

[Dennis Alwon]

Your service disconnect is outside in the meter main. The panel inside is a subpanel and requires ser which is 4 wires. You need a neutral, 2 hots and an equipment grounding conductor. No bonding in the second panel-- everything is done outside at the meter main

 

[ptonsparky]

Your service disconnect is outside in the meter main. The panel inside is a subpanel and requires ser which is 4 wires. You need a neutral, 2 hots and an equipment grounding conductor. No bonding in the second panel-- everything is done outside at the meter main

OP. The hitch here depends on your marking of the meter main. See 230.85(1) & (3). (2) does not apply to your situation.

Your local inspector may disagree.

 

[ActionDave]

Your service disconnect is outside in the meter main. The panel inside is a subpanel and requires ser which is 4 wires. You need a neutral, 2 hots and an equipment grounding conductor. No bonding in the second panel-- everything is done outside at the meter main

That all changed for dwelling units in 2020 code.

 

[infinity]

Your service disconnect is outside in the meter main. The panel inside is a subpanel and requires ser which is 4 wires. You need a neutral, 2 hots and an equipment grounding conductor. No bonding in the second panel-- everything is done outside at the meter main

Although that's the way I would do it under the 2020 NEC it is no longer required to be done that way.

 

[mikeames]

Are you on the 2020 NEC? IMO the meter main should be where the service disconnect is. Prior to the 2020 NEC you would not have the option to use the panel as the service disconnect.

??? Prior to 2020 the main panel was almost always the service disconnect?

 

[Dennis Alwon]

I realize that but have you seen a meter main that was marked "Not for service" Emergency Disconnect. I had not so I assumed that outside disconnect was the service disconnect.

 

[petersonra]

Well I thought with SEU, there was no GEC from meter main to be brought to the panel unless it was in pipe..


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there is only one GEC, regardless of how many grounding electrodes you have. the wires connecting the other grounding electrodes together are bonding conductors.

 

[augie47]

Amazing how the electrons have learned to read.
They react one way if the outside disconnect is an "emergency disconnect" from one that is a "service disconnect"

 

[wwhitney]

Note: if my assumption is wrong, and the new meter main is supposed to be new service equipment, then the SEU must be replaced with SER or another method with an EGC, and your water main GEC must be moved to the meter main.

Minor nit: 250.121 allows a wire type EGC to serve as a GEC as well when it meets the requirements for both conductors.

Cheers, Wayne

 

[wwhitney]

All your Grounding Electrode Conductors go to the same spot as the Main Bonding Jumper.

250.24(A)(1) includes other locations that the GEC(s) may terminate.

Cheers, Wayne

 

[wwhitney]

I realize that but have you seen a meter main that was marked "Not for service" Emergency Disconnect. I had not so I assumed that outside disconnect was the service disconnect.

There's nothing preventing the installer from so marking a meter main. Another thread suggested that some meter main manufacturers are including a sticker with their meter mains for use if desired.

Cheers, Wayne

 

[Dennis Alwon]

There's nothing preventing the installer from so marking a meter main. Another thread suggested that some meter main manufacturers are including a sticker with their meter mains for use if desired.

Cheers, Wayne

I don't think you can do that. If the unit is labeled by the manufacturer as service equipment you can't just write on the panel non service equipment.

 

[wwhitney]

I don't think you can do that. If the unit is labeled by the manufacturer as service equipment you can't just write on the panel non service equipment.

That could possibly be an issue if it is labeled as "Suitable Only for Use as Service Equipment." A discussion on that issue started here:

Cheaper way to install services to fulfill outside safety switch

It may be different if your area, but a meter socket isn't considered service equipment per the NEC. If it's strictly a meter socket change out, you shouldn't have to install the emergency disconnect. Sent from my SM-G781U using Tapatalk Maybe not, but then maybe the service riser is also in...

xenforo.mikeholt.com

But if it's labeled as "Suitable for Use as Service Equipment" there shouldn't be any issue.

Cheers, Wayne

 

[infinity]

That could possibly be an issue if it is labeled as "Suitable Only for Use as Service Equipment."

But if it's labeled as "Suitable for Use as Service Equipment" there shouldn't be any issue.

Cheers, Wayne

IMO they need to rethink the "only" labeling requirement.

 

[winnie]

The NEC has been moving more and more to 'ground and neutral are to be joined at one and only one location' for many years now.

The change to eliminating 3 wire circuits for ranges and dryers, changes to outside feeders, etc.

While IMHO the change permitting the shared neutral between the 'emergency disconnect' and the 'service disconnect' is perfectly reasonable, it is arguably a change in the opposite direction.

Jon

 

[ActionDave]

250.24(A)(1) includes other locations that the GEC(s) may terminate.

Cheers, Wayne

But that would make the grounded/neutral conductor a bonding jumper would it not? That kind of mashes up 250.24(1) with 250.64(F)

 

[SomeRandomPerson]

SomeRandomPerson welcome to the forum. Your thread has come at a time that coincides with a major code change that has a lot of us confused, not just the green apprentices.

Under 2020 code you are allowed what amounts to a "Main Bonding Jumper" in two locations, one outside the house and one inside the house. This was never allowed for the last seventy some years, so a lot of us are trying to work out what this means. I hope you hang in there with the discussion as it evolves and don't get frustrated. Both the old dogs and the new are going to learn something.

Thanks for the encouragement. I just want to know exactly how it’s done


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[wwhitney]

But that would make the grounded/neutral conductor a bonding jumper would it not? That kind of mashes up 250.24(1) with 250.64(F)

I didn't check your references, but I don't see any inherent conflict. The point of the GES is to earth the neutral, so it doesn't matter where that happens between the service entrance and the main panel. The point of the MBJ is to let the EGC system clear a fault (for grounded systems), so it occurs where the EGC originates. The EGC's connection to the GES is a side effect, not the purpose of the GEC.

Cheers, Wayne

 

[SomeRandomPerson]

The NEC has been moving more and more to 'ground and neutral are to be joined at one and only one location' for many years now.

The change to eliminating 3 wire circuits for ranges and dryers, changes to outside feeders, etc.

While IMHO the change permitting the shared neutral between the 'emergency disconnect' and the 'service disconnect' is perfectly reasonable, it is arguably a change in the opposite direction.

Jon

Thanks Jon
Now the labeling gets me a bit confused to. Couldn’t the meter main be considered both and “emergency and a service disconnect” and when do you know which applies?


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