Ricko1980
Member
- Location
- San Francisco
- Occupation
- Electrical Contractor
Hi all,
I've been wondering about this for some time, and thought I'd ask what others are doing.
We're working on a service upgrade for a 2-unit residential building (3 meters, one for each unit and one for the common area). The lowest amperage feeder calculation for each meter is found with a different optional section of 220:
One of the units has their "lowest amperage" calculation when using 220.83 (96A)
One when using 220.82 (97A)
For the house meter, we have demand data and so the lowest calculation is 220.87 (1.8A, including the 125% factor)
Is it permissible to calculate the minimum service amperage by addition of the "best case" calculations for the various feeders?
I feel like the most conservative code approach would be to use the same calculation method for the entire service (i.e., only 220.82), but I'm curious if other people are mixing and matching 220 calculation methods in one building to get a lower service amperage requirement. If we mix and match, we need a 200A service, but if do it all by 220.82, we'd need 250A (bigger wires, more expensive permit, longer utility delay...).
Ricko
I've been wondering about this for some time, and thought I'd ask what others are doing.
We're working on a service upgrade for a 2-unit residential building (3 meters, one for each unit and one for the common area). The lowest amperage feeder calculation for each meter is found with a different optional section of 220:
One of the units has their "lowest amperage" calculation when using 220.83 (96A)
One when using 220.82 (97A)
For the house meter, we have demand data and so the lowest calculation is 220.87 (1.8A, including the 125% factor)
Is it permissible to calculate the minimum service amperage by addition of the "best case" calculations for the various feeders?
I feel like the most conservative code approach would be to use the same calculation method for the entire service (i.e., only 220.82), but I'm curious if other people are mixing and matching 220 calculation methods in one building to get a lower service amperage requirement. If we mix and match, we need a 200A service, but if do it all by 220.82, we'd need 250A (bigger wires, more expensive permit, longer utility delay...).
Ricko