Larger wires at service drop

[Mark A. Timpani, CMI]

Wow this is interesting info! How does the power company know that if the conductors were feeding a 60 amp breaker/service that when they switch the panel to a 300 amp service the wires wont burn up?

I wonder how come in this area they always switch the conductors when they go to a 200 service?

[brian winkle]

Yes you are right about that, when you upgrade to 200 amps going thru the proper channels TEP always brings in a new triplex. That one in the pic looks like what they use for 100 amps. Was there a 200 amp service? It is possible the POCO was not involved, some of us do have the ability to install H taps.

If you want to check on it just call Development Services, ask for the permit counter and ask for a permit history on the address. Anyone can do it and it's free. Keep in mind the City of Tucson and Pima County are in different offices. See if there was a permit for an upgrade, and most importantly, if it was finalized.

[Marc D. Shunk]

Originally Posted by mtimpani

Wow this is interesting info! How does the power company know that if the conductors were feeding a 60 amp breaker/service that when they switch the panel to a 300 amp service the wires wont burn up?

I wonder how come in this area they always switch the conductors when they go to a 200 service?

They have your power bill as history. Every area does it differently. A service upgrade doesn't necessarily trigger a change of the aerial drop.

[brian winkle]

Originally Posted by Marc D. Shunk

They have your power bill as history. Every area does it differently. A service upgrade doesn't necessarily trigger a change of the aerial drop.

The vast majority of upgrades done here are for increased capacity such as for the addition of air conditioning unit(s) or additions to the structure, which would also require additional cooling. A 5 ton AC unit would certainly increase the load, no?

I find it hard to believe that a POCO would actually review past usage to determine if a bigger drop is needed.

I work with the local POCO where the Mark's client is located and I can say without a doubt that if there is a 200 amp main under that mast then something went wrong, a bigger triplex should have been brought in.

[Mark A. Timpani, CMI]

This is the split buss panel.

[brian winkle]

Well Mark we can't see the bus rating from here, but if it were ME I would go with the weakest link and call it a 100 amp service due to the #2 drop.

Did you catch the 6 dissconnect violation?

[Marc D. Shunk]

Originally Posted by brian winkle

Well Mark we can't see the bus rating from here, but if it were ME I would go with the weakest link and call it a 100 amp service due to the #2 drop.

...and you'd have no basis on which to make that claim.

[brian winkle]

Originally Posted by Marc D. Shunk

...and you'd have no basis on which to make that claim.

Could you please explain? And how should he call it?

[Marc D. Shunk]

Originally Posted by brian winkle

Could you please explain? And how should he call it?

He shouldn't. There's nothing wrong.

[brian winkle]

Originally Posted by Marc D. Shunk

He shouldn't. There's nothing wrong.

I didn't mean to imply there was anything wrong, except for the six disco rule,
I meant what size should he/would you call the service?

[Marc D. Shunk]

Originally Posted by brian winkle

I meant what size should he/would you call the service?

If the aerial drop is the only thing you think makes this a 100 amp (it doesn't), then this is a 200 amp service. Only consider items from the point of attachment inward. Seriously, how far back are you going to go? Check the transformer on the pole? Gauge of the primary loop feed? Substation capacity? Certainly not.

Even in the extreme example below, this is still probably a 1600 amp service:

[Mark A. Timpani, CMI]

The breaker that was labeled "main" and had the wires running down to the bottom breakers was 60 amp.

[Mark A. Timpani, CMI]

How far can it go? Can it go from 60a to 300amp?

[Marc D. Shunk]

Originally Posted by mtimpani

How far can it go? Can it go from 60a to 300amp?

They probably would never do that, but the NESC rules are so complex that you could probably get away with that easily. They take into account the span, ice and wind loading, average design temperature, demand load, insulation type, etc. They don't really have a table like the NEC has to look things up in. It's a pretty complex calculation. The power companies do have rules of thumb the linemen work by, but in not every case do they change the aerial drop, nor are they specially obligated to by any rule or law.

[Mark A. Timpani, CMI]

How come the wires don't burn up?