6 meter bases; one 200A service, what?

[zoltrix717]

It was mentioned in an earlier post the this particluar consumer service had 200A coming in and divided into 6 meter bases with 100A main breaker panels to each one. I'm wondering if that's acceptable, and if so, how does that calculate. Here is Canada, the rule for derating this service is like this.. "100 % of the unit with the heaviest load; plus 65% of the next 2 units; plus 40% of the next 2 units; plus 25% of the next 15 units; plus 10% of the remaining units "

 

[jerryb]

Re: 6 meter bases; one 200A service, what?

NEC 230.80 Combined Rating of Disconnects.
Where the service disconnecting means consists of more than one switch or circuit breaker, as permitted by 230.71, the combined ratings of all the switches or circuit breakers used shall not be less than the rating required by 230.79.

NEC 230.79 The service disconnecting means shall have a rating not less than the load to be carried, determined in accordance with Article 220.

NEC Handbook 230.80 In complying with these rules, it is possible for the total of the six overcurrent devices to be greater than the rating of the service-entrance conductors. However, the size of the service-entrance conductors is required to be adequate for the computed load only, and each individual service disconnecting means is required to be large enough for the individual load it supplies.

 

[bphgravity]

Re: 6 meter bases; one 200A service, what?

Also see Section 230.90(A) Exception #3.

 

[zoltrix717]

Re: 6 meter bases; one 200A service, what?

I fail to see the math... I understand that there may by 6 or less disconnecting means to one consumer service, however, if each unit (of the 4) was fed by 100A main breaker, would it not be possible to pull 100A out of each unit? Also I realize there is a difference between the rating of the disconnect ( or breaker) and the computed load, but is there not a minimum size to a dwelling unit of 60A (60 X 4 = 240A) as well?

 

[zoltrix717]

Re: 6 meter bases; one 200A service, what?

sorry, previously i mentioned 6 meter bases, but even 4 doesn't seem to calculate.

 

[bphgravity]

Re: 6 meter bases; one 200A service, what?

It would also be hard for me to be convinced that the calculated load on 4 or 6 units is less than 200A. However, the rules as cited above do have their neccessity in that it may also be unreasonable to be required to install 600A service for 6-100A units or even 400A service for 4-100A units.

I have always been in favor of limiting the service to 50%-60% of the total disconnecting ratings. That would roughly limit 400A worth of service OCD's to a 200A service and 600A worth of service OCD's to 300A. It doesn't always work, but it can be a general rule of thumb.

[ June 18, 2004, 09:01 PM: Message edited by: bphgravity ]

 

[jes25]

Re: 6 meter bases; one 200A service, what?

If I am understanding right you basically figure the load with the v/a per sq. ft and all that, then you add all the units together and that is what size service you need?

[ June 18, 2004, 09:13 PM: Message edited by: jes25 ]

 

[zoltrix717]

Re: 6 meter bases; one 200A service, what?

Does the NEC not have a rule for derating dwelling unit calculations, when there is more than on unit to a building ? or is everything counted as many times as there is units?