VD: 2% plus 3%

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Should service conductors be included in the calculation of "2% VD for feeders"?

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charlie b

charlie b

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Do you include the service conductors as though they were "feeders" in the context of the the NEC guidance that says 2% VD on feeders plus 3% VD on branch circuits provides for reasonable efficiency of operation? I am having a disagreement with a client on this question.
 
When the POCO is required to deliver voltage within a certain range, where is that voltage measurement to be taken? I would think that is where the premises voltage drop calculations should start.

Cheers, Wayne
 
You may not have any control over the size of poco service conductors. In my area, overhead conductors are installed by the poco. It depends on the service point.
 
wwhitney said:
When the POCO is required to deliver voltage within a certain range, where is that voltage measurement to be taken? I would think that is where the premises voltage drop calculations should start.

Cheers, Wayne
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Ours is at the meter.
We verify our voltage readings two times a day through PLC. Occasionally we have an oddball or two that’s about 252 or on the other end about 228, but if they show up a couple of times in an email report we investigate.

Everyone knows POCOs are notorious for running a 200 amp service 300’ overhead with a #2 AL triplex...
 
We are normally sticklers on the Code wording so I would have to say "no" in general terms based on 215.2 FPN in regard to reasonable efficiency.
Art 695 addresses "voltage drop" in general and would seemingly include service conductors and we often include them when calculating AIC so, as a practical matter, I can see them included but based on NEC, "No"
 
my opinion is yes. service conductors do not always come from the POCO. in my view, the situation that this is attempting to address-energy conservation-would be moot in most dwellings and commercial spaces served directly by the POCO. industry is a different story.

all that said, we typically use the maximum connected demand (calculated) which is always higher due to diversity. the period of time where voltage drop would be >5% can likely be measured in hours-perhaps days.
 
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wwhitney said:
When the POCO is required to deliver voltage within a certain range, where is that voltage measurement to be taken?
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Hv&Lv said:
Ours is at the meter.
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Hmm, I was hoping you were going to say "at the service point." Then I would answer "yes" to the poll, as the service conductors are defined to be "The conductors from the service point to the service disconnecting means."

Cheers, Wayne
 
Feeder and service conductors are well defined in the code. If it says feeder conductors, I don't see how that includes service conductors.

OTOH, voltage drop is not really a NEC issue.
 
Years ago Tom Baker was doing a CEU class for us and this exact question came up--

His answer, as best I can remember, and what I have used since then was:

" Service drop, including from POCO, is usually a short run--Forget it and use the entire 5% for the feeders and Branch circuits--Might save a wire size or two in some situations"
 
Hv&Lv said:
Ours is at the meter.
We verify our voltage readings two times a day through PLC. Occasionally we have an oddball or two that’s about 252 or on the other end about 228, but if they show up a couple of times in an email report we investigate.

Everyone knows POCOs are notorious for running a 200 amp service 300’ overhead with a #2 AL triplex...
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PECO/EXELON also great for undersizing feeders. Once did a 100 & a 200 amp service in a long 4 story building. Underground service conductors were fraying rubber covered #6 copper. Amasing how they say #6 wire is large enough to feed 300 amp services.
 
wwhitney said:
Hmm, I was hoping you were going to say "at the service point." Then I would answer "yes" to the poll, as the service conductors are defined to be "The conductors from the service point to the service disconnecting means."

Cheers, Wayne
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Sorry... we do have situations where we are metered at the pole and we get voltage there. The customers 250’ of service wire to their service disconnect isn’t captured in our reads.
In our area the service point is generally “at the meter” or directly above at the top of the mast
 
garbo said:
PECO/EXELON also great for undersizing feeders. Once did a 100 & a 200 amp service in a long 4 story building. Underground service conductors were fraying rubber covered #6 copper. Amasing how they say #6 wire is large enough to feed 300 amp services.
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Our UG would have been 350AL for that
 
Our POCO usually runs a little hot. Usually at least 2 or 3 percent high. And that's usually measured at the service equipment or main panel/switchboard.

The only time I can remember including service conductor voltage drop is when equipment has a voltage regulation tolerance. For example, an Xray machine might 5% voltage regulation from its no-load current to its full rated current.
 
petersonra said:
Feeder and service conductors are well defined in the code. If it says feeder conductors, I don't see how that includes service conductors.

OTOH, voltage drop is not really a NEC issue.
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I agree, start with the origin of the feeder in question and forget about what's ahead of it.
 
This whole discussion can be simplified by referring to ANSI C84.1 Range A or B limits either at the service or for utilization equipment. No need to physically measure the voltage anywhere. Forget the 2% or 3% nonsense and comply with ANSI C84.1 since that establishes the minimum and maximum limits.


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Xptpcrewx said:
This whole discussion can be simplified by referring to ANSI C84.1 Range A or B limits either at the service or for utilization equipment. No need to physically measure the voltage anywhere. Forget the 2% or 3% nonsense and comply with ANSI C84.1 since that establishes the minimum and maximum limits.


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Ok. What is it?
 
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