Voltage Drop Question

[mystereons41]

Hi all, I’m working on putting electric service on my land and have a voltage drop question. I’ll be installing a meter pedestal with a breaker panel and outlets in phase one of installation before winter. I’ll be doing underground to the pedestal somewhere between 15 and 100 ft from the pole, depending on how much time I have to trench. My final build location is about 300 ft from the pole. I’m trying to figure what are allowable voltage drops between different points. I’m reading NEC allows 3% for feeders/branch circuits and 5% total combined between feeder and branch. So between the pedestal and main breaker at future house would be 3% max, and 5% total from meter pedestal to farthest outlet. Is that correct? My main question is, what is the recommended voltage drop for the service conductors going to the meter pedestal? Especially if I end up going the 100 ft. If I already have 3% between pedestal and house, is it going to be a problem to have 3% between service drop and the pedestal? Thanks!

 

[ptonsparky]

What do you think will be the actual load? Not calculated service size.

Using the NEC calculated load and 3% for VD should be more than adequate for sizing the conductors when used with the actual load. A 200 amp service will never see a 200 amp load in real life.

 

[roger]

My final build location is about 300 ft from the pole. I’m trying to figure what are allowable voltage drops between different points. I’m reading NEC allows 3% for feeders/branch circuits and 5% total combined between feeder and branch.

The NEC only recommends 3 and 2, it does not mandate it.

Roger

 

[Julius Right]

First, in my opinion also NEC does not require 3% and 5% but recommends it. The utility has to keep the supplied voltage limit as per ANSI C84.1-2020.[from rated]
Service Entrance Voltage High Range A=105%
Service Entrance Voltage Low Range A=95%
Service Entrance Voltage High Range B=104.2%
Service Entrance Voltage Low Range B=91.70%
Utilization High Voltage Range A=105%
Utilization Low Voltage Range A=90%
Utilization High Voltage Range B=105.8%
Utilization Low Voltage Range B=86.7%
The installation will be executed in such a way that range A is preserved
Range B is allowed limited in time until the repair work is completed.
In the design of the installation will be considered range A

 

[mystereons41]

What do you think will be the actual load? Not calculated service size.

Using the NEC calculated load and 3% for VD should be more than adequate for sizing the conductors when used with the actual load. A 200 amp service will never see a 200 amp load in real life.

Hi, ok thanks for the tip. We haven’t designed the house yet, so not sure on the exact load. The house will probably be on the small side. I’m sure I could sit down and at least get a ballpark idea though. Thanks!

 

[mystereons41]

First, in my opinion also NEC does not require 3% and 5% but recommends it. The utility has to keep the supplied voltage limit as per ANSI C84.1-2020.[from rated]
Service Entrance Voltage High Range A=105%
Service Entrance Voltage Low Range A=95%
Service Entrance Voltage High Range B=104.2%
Service Entrance Voltage Low Range B=91.70%
Utilization High Voltage Range A=105%
Utilization Low Voltage Range A=90%
Utilization High Voltage Range B=105.8%
Utilization Low Voltage Range B=86.7%
The installation will be executed in such a way that range A is preserved
Range B is allowed limited in time until the repair work is completed.
In the design of the installation will be considered range A

So is the Service Entrance Voltage that has to be maintained at a certain range by the utility considered to be at the pole, or at the meter pedestal? I found online that it’s considered to be “at the point of delivery.” But looking for clarification. Thanks!

 

[roger]

So is the Service Entrance Voltage that has to be maintained at a certain range by the utility considered to be at the pole, or at the meter pedestal? I found online that it’s considered to be “at the point of delivery.” But looking for clarification. Thanks!

Look at the definition of Service Point in article 100

Roger

 

[mystereons41]

Look at the definition of Service Point in article 100

Roger

From Article 100:

Service Point. The point of connection between the facilities of the serving utility and the premises wiring.

To me that sounds like it would be the meter pedestal?

 

[ptonsparky]

From Article 100:

Service Point. The point of connection between the facilities of the serving utility and the premises wiring.

To me that sounds like it would be the meter pedestal?

Depends. Does your utility maintain the drop or lateral to the house if the meter is on a pole? Some do.

 

[kwired]

From Article 100:

Service Point. The point of connection between the facilities of the serving utility and the premises wiring.

To me that sounds like it would be the meter pedestal?

That would be pretty common in situation with such a pedestal, and even then it may be line side or load side is where the transition occurs. It could be at any point. Usually will be no further "downstream" than the service disconnecting means though. If customer owns and maintains the transformer service point could be some point in the medium/high voltage lines - and does happen that way with some industrial applications.