Is a main breaker required for a meter stack?

[steve66]

I usually specify a main breaker before the service conductors hit a meter stack, or before they are spliced and tapped off to go to individual meters. I just hate to see a bunch of distribution with unprotected wire.

But is this required? Of can the service conductors come straight from the utility transformer (3 phase) and into a pull section or bussed section of a meter stack? Then the first circuit breakers would be after the meters.

For example, would this be legal: 3 sets of 600 KCM coming from the utility transformer, landing on a meter stack bussed section, and then going to (6) 200A meters, each with a 200A breaker on the load side of the meter??

Thanks: Steve

 

[Jljohnson]

For example, would this be legal: 3 sets of 600 KCM coming from the utility transformer, landing on a meter stack bussed section, and then going to (6) 200A meters, each with a 200A breaker on the load side of the meter??

Thanks: Steve

Yes, perfectly legal to not have a main breaker in this situation.

 

[raider1]

Yes, perfectly legal to not have a main breaker in this situation.

Agreed, check out 230.71 and 230.72.

Chris

 

[cdcengineer]

You better check with the local utility. Here in Colorado, XCEL & Holy Cross (the (2) utilities I deal with regularity) have different requirements for hot and cold sequence metering depending on residential or commercial metering. The utility should publish a metering & use guidebook or metering standards.

 

[steve66]

Yes, I forgot about the 6 disconnect rule. It was just a conciendence I used 6 breakers in my example.

And thanks for the input about the utility.

Are tapps allowed on the service conductors also? Could I tap off the 500 KCM feeders, and run 3/0 to each meter stack? I always thought taps wern't allowed for service conductors, and they were limited to feeders.

If the service conductors were tapped, would they have to be tapped into each set of 500KCM? Or could I use each set of 500's to feed (2) 200 amp meters?

 

[hurk27]

I would feel this would depend upon whether the meter stack is supplying one building or many separate buildings, take a mobile home park, we have many that have 12-24 meter stacks that have no main ahead of them, this is because 230.70 only applies to one building (230.2), and only applies where the conductors from a disconnect enters a single building (230.70) so you might have a strip mall, where each occupancy is separated by a certified fire wall that would determine each to be a separate building, so if this is the case, there would only be a requirement to limit the Maximum Number of Disconnects to each occupancy (230.71), another place would be where you have several buildings lets say numbered 1 thru 10 if a 10 position meter stack was on the outside of building 1, and only had one set of feeders from it that went into building 1, but the rest of the feeders went back into the ground and fed buildings 2 thru 10 without going into building 1, then I could not see a requirement for a disconnect ahead of the stack.

Charlie Eldridge posted a diagram of this he showed at the state and Western Section IAEI meetings, which shows this in exact detail, I'll see if I can find it.

 

[LEO2854]

I usually specify a main breaker before the service conductors hit a meter stack, or before they are spliced and tapped off to go to individual meters. I just hate to see a bunch of distribution with unprotected wire.

But is this required? Of can the service conductors come straight from the utility transformer (3 phase) and into a pull section or bussed section of a meter stack? Then the first circuit breakers would be after the meters.

For example, would this be legal: 3 sets of 600 KCM coming from the utility transformer, landing on a meter stack bussed section, and then going to (6) 200A meters, each with a 200A breaker on the load side of the meter??

Thanks: Steve

I would love to see a disco be for any equipment so you can change componits after the feed ,, But it is legal otherwise.

 

[e57]

Yes, I forgot about the 6 disconnect rule. It was just a conciendence I used 6 breakers in my example.

And thanks for the input about the utility.

Are tapps allowed on the service conductors also? Could I tap off the 500 KCM feeders, and run 3/0 to each meter stack? I always thought taps wern't allowed for service conductors, and they were limited to feeders.

If the service conductors were tapped, would they have to be tapped into each set of 500KCM? Or could I use each set of 500's to feed (2) 200 amp meters?

The service conductors could be tapped - but tap rules apply - however once you tap them and stick in another two meters(?) - Are you adding more than 6(?) -the additional 2 disconnecting means exceed the 6 disconnect rule.... You would need a main, or split into sets of whatever quanity below 6.... At that point you may as well have a single main.

However if you just have 6, and at any further point addition disconnects needed to be added - you would be screwed.... :roll:

As for the sizes mentioned - you would need to do a load calc.... One each for the taps to each, and the combined total for the main set of SEC's. They - the service conductors - are not necessarily sized by the OPC on the other side of them... The feeder on the other side would be - unless you sized the OCP for the load... (Which seems to a less common point of sale these days... Everyone seems to want big round numbers on breakers... Selling superfluous capcity...)

 

[steve66]

All good answers. Thanks.

The service conductors could be tapped - but tap rules apply - however once you tap them and stick in another two meters(?) - Are you adding more than 6(?) -the additional 2 disconnecting means exceed the 6 disconnect rule.... You would need a main, or split into sets of whatever quanity below 6.... At that point you may as well have a single main.

However if you just have 6, and at any further point addition disconnects needed to be added - you would be screwed.... :roll:

Its more a general question - I don't have a specific project that this applies to right now. Like I said, I generally specify a main fused disconnect or breaker. However, I'm seeing a lot of designs by other people who don't include a main disconnect.

Good point about having to add a 7th disconnect though. But that's a decision I'd usually let the owner of a project make: Do they want to spend a little more right now and be able to easily expand? Or do are they more interested in saving money up front?

 

[e57]

All good answers. Thanks.



Its more a general question - I don't have a specific project that this applies to right now. Like I said, I generally specify a main fused disconnect or breaker. However, I'm seeing a lot of designs by other people who don't include a main disconnect.

Good point about having to add a 7th disconnect though. But that's a decision I'd usually let the owner of a project make: Do they want to spend a little more right now and be able to easily expand? Or do are they more interested in saving money up front?

It was a 'general' answer too.... That said - a single main can simplify quite a lot on the labor and planning side - to where it can actually be a savings IMO. Sometimes plans change before the job is done...