Voltage drop for service conductors?

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iwire said:
I agree, do the NEC service calculations and you are already oversized but beyond that when the calculations come out to say 150 amps or 125 amps or even as little as 90 amps guys will roll up to 200 amp service 'just in case'.
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Yes oversized as far as calculations, but, 160' away is still a far stretch to use 4/0 aluminum for a 200 amp feed but that's just my opinion.

JAP>

In my case the overhead service conductors swung from a pole mounted transformer to the eave of the house in open air to a 200a riser and meter base mounted on an outside wall to a 200a Main Breaker Panel just inside.

When the customer needed the overhead put underground so he could build his shed, the underground pipe and wire from the existing meter on the house back to the utilty pole and up to the transformer became his responsibility.

The overall length of the 4/0 aluminum underground was then pushing 165'.

Just to say that prior to the change, any voltage drop from the Pole top Transformers to the house would have been the Power Company's problem, where now it becomes the customers problem should there happen to be one.

JAP>
 
jap said:
Yes oversized as far as calculations, but, 160' away is still a far stretch to use 4/0 aluminum for a 200 amp feed but that's just my opinion.

JAP>

In my case the overhead service conductors swung from a pole mounted transformer to the eave of the house in open air to a 200a riser and meter base mounted on an outside wall to a 200a Main Breaker Panel just inside.

When the customer needed the overhead put underground so he could build his shed, the underground pipe and wire from the existing meter on the house back to the utilty pole and up to the transformer became his responsibility.

The overall length of the 4/0 aluminum underground was then pushing 165'.

Just to say that prior to the change, any voltage drop from the Pole top Transformers to the house would have been the Power Company's problem, where now it becomes the customers problem should there happen to be one.

JAP>
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I wouldn't worry about it. Sounds like you will have less vd now because the conductors will be much larger the whole way.

IMO, my rule of thumb for calculating vd at a typical dwelling is at 70 amps.
 
ActionDave said:
I'd say that's a pretty good number. I fired up everything thing I could in my house and didn't break 80A.

I'll bet on an average day an average home with a 200A service won't draw more than more than 40A.
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Unless you happen to have electric space heating and electric DHW. That may not be "average", but it certainly is common.

The VD game is also very different if there is a tankless electric water heater.
 
The only reason it makes me stop to think about it for a while is because we're taking an existing overhead service, where the overhead service conductors are 110' form the pots on the pole to the weather head in open air.

Now take that same service and go underground in a 30" deep ditch and your roughly 10' up on the house end, 110' to the utility pole, 5' up to get to 2' above ground level, and , leave 35' out per their requirements for them to terminate and you've gone from 110' overhead service conductors to 160' of underground service conductors very quickly.

JAP>
 
jap said:
The only reason it makes me stop to think about it for a while is because we're taking an existing overhead service, where the overhead service conductors are 110' form the pots on the pole to the weather head in open air.

Now take that same service and go underground in a 30" deep ditch and your roughly 10' up on the house end, 110' to the utility pole, 5' up to get to 2' above ground level, and , leave 35' out per their requirements for them to terminate and you've gone from 110' overhead service conductors to 160' of underground service conductors very quickly.

JAP>
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But you could easily go three or four hundred feet of 4/0 service conductor and not have a problem.
 
jap said:
That's probably true by the math.

JAP>
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It is true by the math. In reality one could go sixteen hundred feet and not have a problem. Find me something in a house that can't tick away just fine with ten percent voltage drop, even twenty percent.

At my house it's roughly 20' down the pole to a meter pedestal, whatever size wire the POCO used I don't know, 90' underground 4/0Al to a 200A main breaker panel with two 100A breakers tied to 1/0Al that go to two sub panels each about fifty feet away. I didn't do a voltage drop calculation on any of it because I put it all in before VD calculators were so easy to get online.
 
ActionDave said:
It is true by the math. In reality one could go sixteen hundred feet and not have a problem. Find me something in a house that can't tick away just fine with ten percent voltage drop, even twenty percent.

At my house it's roughly 20' down the pole to a meter pedestal, whatever size wire the POCO used I don't know, 90' underground 4/0Al to a 200A main breaker panel with two 100A breakers tied to 1/0Al that go to two sub panels each about fifty feet away. I didn't do a voltage drop calculation on any of it because I put it all in before VD calculators were so easy to get online.
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So here we talk about no need to upsize wire yet in your own house you have 1/0 Aluminum used for a 100 amp feeder?

That's funny. :)


JAP>
 
ActionDave said:
Unless the house has a lot of electric heat a 200A service is already upsized and would not need larger wire.
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I agree, outside of homes with electric heat or instant electric water heaters, you seldom can go in and clamp on a meter and read more then 50 -60 amps of load.


JAP>[/QUOTE]

jap said:
So here we talk about no need to upsize wire yet in your own house you have 1/0 Aluminum used for a 100 amp feeder?

That's funny. :)


JAP>
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He may have had a situation where 1/0 cable is more readily available then 1 AWG cable?
 
kwired said:
He may have had a situation where 1/0 cable is more readily available then 1 AWG cable?
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If it were cable it would have required a 1/0 for a 100a feeder since #1 cable would only be rated for 85 in the 60d column and the next standard size would be a 90 amp breaker would it not?

JAP>
 
jap said:
If it were cable it would have required a 1/0 for a 100a feeder since #1 cable would only be rated for 85 in the 60d column and the next standard size would be a 90 amp breaker would it not?

JAP>
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The 60C rule is more academic than practical, as most equipment is listed otherwise for 75C. Also, service conductors only need 83% of the ampacity of the service rating & service OCPD, for residential 400A and less.
 
Carultch said:
The 60C rule is more academic than practical, as most equipment is listed otherwise for 75C. Also, service conductors only need 83% of the ampacity of the service rating & service OCPD, for residential 400A and less.
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Under 2011 and earlier editions, #2 AL is good for a 100A service [310.15(B)(7)].
 
jap said:
So here we talk about no need to upsize wire yet in your own house you have 1/0 Aluminum used for a 100 amp feeder?

That's funny. :)


JAP>
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The point is I have a 200A service and several hundred feet of wire before I hit my first branch circuit, and in my case some of it is smaller than 4/0, and I don't have a voltage drop problem.
 
jap said:
If it were cable it would have required a 1/0 for a 100a feeder since #1 cable would only be rated for 85 in the 60d column and the next standard size would be a 90 amp breaker would it not?

JAP>
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Kind of caught me there, yes for NM or SE cable which are more likely in residential application, other cable types could be #1.

Carultch said:
The 60C rule is more academic than practical, as most equipment is listed otherwise for 75C. Also, service conductors only need 83% of the ampacity of the service rating & service OCPD, for residential 400A and less.
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In Actiondave's case they were not feeding the entire load of a dwelling.
 
ActionDave said:
The point is I have a 200A service and several hundred feet of wire before I hit my first branch circuit, and in my case some of it is smaller than 4/0, and I don't have a voltage drop problem.
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I have a 150 on my house with about 100' of 2/0 alum to the house and don't have never had any problems either.

I've always put too much concern on voltage drop when it comes to someone else's service since I'm never sure what all they'll have or complaints about the lights dimming.

It's re assuring hearing others perspective on the issue.



JAP>
 
ActionDave said:
I'd say that's a pretty good number. I fired up everything thing I could in my house and didn't break 80A.

I'll bet on an average day an average home with a 200A service won't draw more than more than 40A.
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That number is even lower in an all-gas house, or a house with oil heat/hot water and electric dryer and stove.
 
Smart $ said:
Under 2011 and earlier editions, #2 AL is good for a 100A service [310.15(B)(7)].
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I'm aware of 310.15B7. The algorithm has changed in 2014 to one common correction factor instead of the table, but the results remain the same as they did in 2011, when 75C terminal ampacity is your starting point.
 
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