What determines service size?

[VoltageHz]

Is there a universal specification that determines the size of a service across many different situations?

If you have the service entrance conductors sized for 200 Amps and the meter pan rated for such, but the main panel has a 150 Amp breaker, what size service is that?

If you have a service in a multi-family house with multiple panels with different size main breakers, how to determine that size service?

 

[LarryFine]

Is there a universal specification that determines the size of a service across many different situations?

For the minimum service for a specific premises, you need to do load calcs. For a given service, the weakest link is the limit.

If you have the service entrance conductors sized for 200 Amps and the meter pan rated for such, but the main panel has a 150 Amp breaker, what size service is that?

It sounds like a 150a service that could be upped to 200a to me.

If you have a service in a multi-family house with multiple panels with different size main breakers, how to determine that size service?

The limiting factor in the main service is, well, the limiting factor. Is there a main for the building?

 

[VoltageHz]

For the minimum service for a specific premises, you need to do load calcs. For a given service, the weakest link is the limit.

It sounds like a 150a service that could be upped to 200a to me.

The limiting factor in the main service is, well, the limiting factor. Is there a main for the building?

I'm speaking speculative here, curiosity only.

So the main breaker alone is what determines the service size?

What if there are multiple main panels (each fed with it's own meter) with different size main breakers?

 

[Rewire]

Services are sized to the calculated load. The service for a multi family dwelling is calculated based on the load of each dwelling applying appropiate demand factors.

 

[brantmacga]

What if there are multiple main panels (each fed with it's own meter) with different size main breakers?

It would be whatever kw the meter stack is rated for. you wouldn't necessarily rate the service as the sum of the rating for each disconnect.

 

[Rewire]

you can have an 800 amp service with 5 200 amp breakers

 

[Volta]

Determine the required size by calculations.
Determine the actual/existing size by the weakest link, as Larry said.

 

[jaylectricity]

You don't size the service. You size the conductors, you size the conduits, you size the overcurrent protection. You don't size the service.

 

[iMuse97]

I'm speaking speculative here, curiosity only.

So the main breaker alone is what determines the service size?

What if there are multiple main panels (each fed with it's own meter) with different size main breakers?

1. multiple panels with separate meters could be multiple services; I've done work at a building with several laterals/drops to the facility.

2. the weakest link determines the service size, and then the main OCPD must be sized to protect that weakest link.

 

[Pierre C Belarge]

First, the number of services is determined by the number of laterals or service drops.


A single service drop can supply more than one set of service entrance conductors. Each set of service entrance conductors can serve up to 6 disconnecting means.


If there is 1 service disconnecting means, the size of the service is generally determined by the rating of the single disconnecting means and sized according to 230.42.



There may be multiple service disconnecting means supplied from one service drop. The size of the conductors supplying the multiple disconnecting means is per 230.90 ex #3.

At this point, I have heard all kinds of electricians call the size of the service all kinds of numbers.

You may have 2 sets of 500Kcmil supplying 5 sets of 200A rated disconnecting means. Some may call it an 800A service. Although the load may actually be less than 800A.

 

[Jerseydaze]

you can have an 800 amp service with 5 200 amp breakers

I know you can do this but dont understand isnt there unlikely potential of drawing more current then the feeders are sized for and protected for down the road ?

 

[satcom]

I my town many of the utility drops are #10 open air and when someone upgrades their service to 200A the service drop stays.

 

[Rewire]

I know you can do this but dont understand isnt there unlikely potential of drawing more current then the feeders are sized for and protected for down the road ?

Thats why it is up to the EC to do a load calculation when adding new load to an existing service.

 

[satcom]

Thats why it is up to the EC to do a load calculation when adding new load to an existing service.

That is a good issue, how many EC's do the required load calculations on service upgrades?