Service Ampacity - InspectionNews

Matthew Barnicle · #1 (**permalink**) 03-12-2008, 10:37 AM

What would you rate this service at?

1/0 Copper Service Entrance Conductors
Service Equipment panel had 3 Breakers for means of main disconnect.
100A to house panel
30A to pool panel
60A to HVAC package unit panel

Service Equip. Panel had no ampacity rating visible on label.

Raymond Wand · #2 (**permalink**) 03-12-2008, 12:02 PM

If its 1/0 its rated upto 150 amps.

Jon Randolph · #3 (**permalink**) 03-14-2008, 08:44 AM

The rating that you give the service should be the smaller of the SEC, panel rating or main isconnect rating. Make sure that you are looking at the lines from the mast to the pole also and not just from the meter to the main.

Without a legible lable on the panel, I would state that I could not verify the size of the service and state why.

Make sure that you do not rate it at more than it is capable of or you may be upgrading it youself.

Lanny Freng · #4 (**permalink**) 03-14-2008, 11:05 AM

Dont forget to take into account the meter as well, Older ones are not rated as high as newer ones. somewhat of a rule of thumb. round = 60 amp, square = 100 amp, rectangular = 150+

Jerry Peck · #5 (**permalink**) 03-14-2008, 01:08 PM

Quote:

Originally Posted by Jon Randolph

The rating that you give the service should be the smaller of the SEC, panel rating or main isconnect rating.

Except, as in this case, when there are multiple main disconnects, then the smaller of the service entrance conductor rating or the combined rating of the multiple mains. While multiple mains cannot be combined to get a true rating, they can be combined to get a 'maximum rating', and if that is smaller than the service entrance conductors, then that 'maximum rating' would be the service size, i.e., being the smaller of the two.

In the case stated above:
1/0 Copper Service Entrance Conductors
Service Equipment panel had 3 Breakers for means of main disconnect.
100A to house panel
30A to pool panel
60A to HVAC package unit panel

The 1/0 copper is rated for 175 amps, the 3 multiple mains add up to 190 amps, thus the service size is 175 amps.

Eric Barker · #6 (**permalink**) 03-14-2008, 07:06 PM

Around here you cannot take into account the size of the overhead drop. First of all, the utility can put in whatever gauge they want up to the house and no one can say boo about it. Second, the overhead conductors are surrounded by air, an insulator not found around the conductors in the home wiring. Therefore, "standard" ratings do not apply.

Jerry Peck · #7 (**permalink**) 03-14-2008, 08:13 PM

Quote:

Originally Posted by Eric Barker

Around here you cannot take into account the size of the overhead drop.

Eric,

Should not be concerned with the size of the overhead service drop anywhere (unless it's #10 wire

).

We are talking about the "service entrance conductors", not the "over head service drop conductors".