[glen4cindy]

I was looking at my service entrance the other day.

My service panel and meter base and service entrance were all upgraded to a 200-amp service just prior to my purchase of this house.

I was noticing the remarkable difference in size between the feeder wire from the pole and the cables it is joined to in the weatherhead.

Obviously, this is okay, but I'm curious as to why?

Can someone explain this?

Thanks in advance.

 

[brric]

POCOS operate under a different set of guidelines. Therefore the conductors to the weather head are usually smaller than those to the meter.

 

[seharper]

That's very typical. The power company "upgrades your service" by having you upgrade the stuff you install (panel, meter, service entrance) and then they just move the same old wires onto it! So they haven't upgraded your service drop at all.

The power company's trick is that they watch your meter/usage (particularly, the smart meter will give them second-by-second reports of peak current draws). When that telemetry says you need a bigger service drop, they'll send out a truck and upgrade your service drop. They're betting that won't be necessary in 98% of cases.

 

[Datawise]

In addition, there are different ratings for "free air" cable and "enclosed" cables / wires.

Most utilities will stock only a few different sizes of wires, transformers, etc. For them it is less expensive to change out the odd wire / transformer, then to install any number of different sized ones as needed; some are over-sized, some are undersized.

Cheers
John

 

[u2slow]

In addition, there are different ratings for "free air" cable and "enclosed" cables / wires.

^ That is the main reason.


The next one is that utilities do not follow the same code(s) that electrical contractors are required to. They basically have their own demand-calculation formulas, and only use a couple of common cable sizes for everything. Electric heat tends to drive up the cable size too.

 

[seharper]

^ That is the main reason.

So if that were an overhead-line 200A feeder (and thus under NEC) running between two buildings, what wire size would NEC allow for the overhead wire between the two weatherheads?

Is that the same as the PoCo is allowed under their rules?

 

[Datawise]

Notwithstanding other factors, likely in the CEC you would need / want 1/0 AL wire. The POCO will use 1/0 for anything up to 400 amps I would expect. For up to 200 the POCO is generally using #3 AL.

The last 400 amp I did, the POCO used 1/0 AL for the OH line.

All of that to say that I expect the NEC to be similar.

Cheers
John

 

[Shadow99]

So if that were an overhead-line 200A feeder (and thus under NEC) running between two buildings, what wire size would NEC allow for the overhead wire between the two weatherheads?

Is that the same as the PoCo is allowed under their rules?

Technically you could use the free air ampacity tables for the overhead part, but as soon as you go into conduit, your back down to cables in the conduit table.


fwiw, #2 AL ACSR triplex is rated for 184A.

 

[u2slow]

Is that the same as the PoCo is allowed under their rules?

I can't speak for the NEC.



The PoCo typically uses smaller overhead wire - ahead of the meter - than if you were to do overhead wire (subfeed) to a detached building.

 

[seharper]

Technically you could use the free air ampacity tables for the overhead part, but as soon as you go into conduit, your back down to cables in the conduit table.

fwiw, #2 AL ACSR triplex is rated for 184A.

Yes, I'm assuming you'd have a crimp up at the weatherhead between the overhead wire and the much larger wire that runs down the conduit.