Residential electrical service

[andy32821]

Hi,
I'm in Orange County Fl. I wish to upgrade my main panel (outside next to the meter) from a 125 amp to a 175-amp service.
The service entrance cable from the transformer to the meter is 1/0 aluminum direct burial cable (60-foot transformer to meter).
The power company's lineman that verified the size tells me that should be fine for a 200-amp service.
(I have an EC license (inactive) but I'm an automation guy and not familiar with all the codes involved.)

Trying to calculate from the code it seems like I will be limited to somewhat less than a 200-amp service.
When I hire an electrical contractor to do an upgrade. what is the maximum service the EC's engineer is going to allow on this existing 1/0 alum cable?
(Power company has approved a 200-amp service as far as the load on the transformer)

Andy

 

[Dennis Alwon]

The power company has their own rules on what their transformer can handle and what size wire is needed. Their wire sizes are smaller than the nec will allow but they are not guided by the NEC

I have never seen a 175 amp service. You need to use 200 amp as your service

 

[W@ttson]

here is the chart for the old table where the new rules basically do the same but in word form:



If you are aluminum and shooting for 200A, you are looking at 4/0

 

[augie47]

That chart is correct for any of your (customer) wiring but, as Dennis states, POCO follows a different guideline. For practical purposes you can ignore their wire sizes.

 

[andy32821]

That chart is correct for any of your (customer) wiring but, as Dennis states, POCO follows a different guideline. For practical purposes you can ignore their wire sizes.

Hi Augie,

That's what is confusing me.

The lineman seems to say the underground feed from the transformer to the meter is Duke property (meaning performing conductor sizing using the utility's codes), but I get the impression from the NEC the conductors are my scope and I have to basically use the above chart.

 

[augie47]

If the conductors are under control of POCO (Duke), pretty much standard procedure, you need not worry about them, Your Code key is "Service Point",, That is determined by POCO (commonly the meter base on underground services) and any wiring ahead of that does not fall under NEC rules.

 

[topgone]

Hi Augie,

That's what is confusing me.

The lineman seems to say the underground feed from the transformer to the meter is Duke property (meaning performing conductor sizing using the utility's codes), but I get the impression from the NEC the conductors are my scope and I have to basically use the above chart.

Anything beyond the meter is your responsibility and not the utility's responsibility, IMO.

 

[GoldDigger]

For an overhead service POCO will often define the "service point" as the junction at the weatherhead rather than at the meter. So the riser in the weatherhead may or may not be under NEC even when the customer electrician supplies and pulls that wire. POCO will still want to require physical security on access to the wires all the way to the meter.

But for underground service, where POCO stubs up their conductors directly into the meter base, it is extremely unlikely that the service point would be anywhere upstream of the meter.

It is also possible but less likely for POCO to define the service point downstream from the meter, where the meter is at the pole base but POCO service conductors extend to the disconnect(s). I do not think the service point can ever be downstream of the service disconnect. The status of the integral bus in a meter/main enclosure may be hard to determine.

 

[tom baker]

Pocos typically on carry 2 and 6 triplex on line trucks. These conductors are in free air so are smaller than what we see in the NEC. Plus your 200 Amp service will never see 200 amps, 100 maybe

 

[suemarkp]

I (had) a 200A service fed with 100' of #2 aluminum overhead and another 150' of 1/0 aluminum underground. I reduce my main from 200A to 150A because of voltage drop and overloading concerns. In the end, amps and amps and insulation damge is the same whether in the NEC side, the NESC (POCO) side, in Canada or Europe. I figured people are going to add loads and not do a calculation. That 150A main is still pushing the wires to me, as they will be hitting over 90C if that 150A breaker ever trips from overload.

The inspector told me I didn't need to do that, but I may add solar one day and cutting the main down also gives more headroom for solar capacity. I doubt my 150A service ever goes over 100A even though it calculates above that. I realize that is why the NESC tables are lower. But if that's the case, the 150A breaker should not trip on overload either.

It would be nice if we could get a way to make a reliable calculation so we have wires being protect appropriately as not assuming the calculation is overly conservative.

 

[kwired]

I (had) a 200A service fed with 100' of #2 aluminum overhead and another 150' of 1/0 aluminum underground. I reduce my main from 200A to 150A because of voltage drop and overloading concerns. In the end, amps and amps and insulation damge is the same whether in the NEC side, the NESC (POCO) side, in Canada or Europe. I figured people are going to add loads and not do a calculation. That 150A main is still pushing the wires to me, as they will be hitting over 90C if that 150A breaker ever trips from overload.

The inspector told me I didn't need to do that, but I may add solar one day and cutting the main down also gives more headroom for solar capacity. I doubt my 150A service ever goes over 100A even though it calculates above that. I realize that is why the NESC tables are lower. But if that's the case, the 150A breaker should not trip on overload either.

It would be nice if we could get a way to make a reliable calculation so we have wires being protect appropriately as not assuming the calculation is overly conservative.

changing from 200 to a 150 amp main breaker just limits how much current can be drawn before the breaker trips.

If you still have same load on the same conductors voltage drop will still be the same.

 

[suemarkp]

Yes. It is bad enough now. Dont want someone thinking they can easily add another 80A of load.

 

[Hv&Lv]

This is what we go by “for the most part”.
this is continuous ampacity, and we can add diversity factors.
I run 2/0 to some 320 amp services depending on length and the fuel supply.

 

[infinity]

This is what we go by “for the most part”.

Just curious why the code words?

 

[Little Bill]

Just curious why the code words?

Those are wire brands.

 

[LarryFine]

Those are wire brands.

 

[Little Bill]

View attachment 2563478

I know Sweetbriar is for sure.

 

[cadpoint]

Construction Tool Box - Duke Energy via a google search

Up in the top right it should be Florida. There are other States listed in the pulldown menu.
You don't need to register to read any of the linked information.

I never saw any chart or listing on AWG or the like stated in post #3 or #13, nor in this one below.

Requirements for Electrical Service and Meter Installations -Duke Energy 128 pages

All you want to do to get to a meter!
I like looking at tech illustrations, I'm at ate up with it...

 

[kwired]

Those are wire brands.

More like a product name regardless of which company produced it. Sweetbriar is 4/0, 4/0 2/0 Monmouth is 4/0, 4/0, 4/0. The chart posted only tells us the phase conductor size, the reason same size sometimes appears twice is one is with full neutral and one is with a reduced neutral.

 

[dgutshall]

The power company I work for in Nevada 2/0 AL is the minimum conductor size for services. There should be an engineer you can contact at the company to verify their requirements