Voltage Drop Calc based on Service Rating rather than actual Load

E

EC_JJ

Member
Location
Florida
Occupation
Electrical Contractor
Good morning,

I am having an issue with the "Building Official" at City of Westlake.

I have an irrigation timeclock only (no pump) for which we have a standalone service rack. #6 cu for the service lateral and feeders, 60 amp main. The load can't be more than 2-3amps. The rack is 400 feet from the transformer and the inspector/building official is claiming I need to provide a voltage drop calculation and the amperage figured in the calculation needs to be the 60-amp service rating, not the actual load.

I explained to him my understanding that voltage drop calculations are not a code requirement, but rather a recommendation, primarily for the engineer (if distance is known) and/or the contractor (if distance is determined in the field), for appliance performance/efficiency. Secondly, the voltage drop applies only to feeders and branch circuits, not service laterals. Lastly, the connected load is the amperage used in the calculation, not the service rating.

Is it me or is this guy off his rocker? I am being forced to run 400' of 2/O copper in 2" pvc for a 2-3 amp irrigation timer (sitting in a 4 ckt N3R panel)...
 
electrofelon said:
Ask him for a code reference, it is not an NEC requirement, but could be a local or energy code in which case he could be correct depending on what the actual wording is.
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I did, he could not provide one. He's just pulling his AHJ card with no justification.
 
As electrofelon notes it may well be an energy code requirement. FL is under the 2021 Code I believe which states:

C405.5.3 Voltage drop.​

The conductors for feeders and branch circuits combined shall be sized for a maximum of 5 percent voltage drop total.
 
augie47 said:
As electrofelon notes it may well be an energy code requirement. FL is under the 2021 Code I believe which states:

C405.5.3 Voltage drop.​

The conductors for feeders and branch circuits combined shall be sized for a maximum of 5 percent voltage drop total.
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Augie, I'm not sure that this would apply. The conductors in question are neither feeder not branch circuits. Even if they were the load is only 2-3 amps so why would the VD calculation be required to be based on the 60 amp service size?
 
infinity said:
Augie, I'm not sure that this would apply. The conductors in question are neither feeder not branch circuits. Even if they were the load is only 2-3 amps so why would the VD calculation be required to be based on the 60 amp service size?
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I would agree but before the OP took a stand based on the NEC, I just thought might want to be aware of a possible energy code input, I don;t know how FL will address it.
 
It's interesting that just specifies a VD for feeders and Branch circuits and not service conductors. Also if they are going to have a such a requirement I think they should specify specifically what value to use for the current in the calculation.
 
electrofelon said:
Also if they are going to have a such a requirement I think they should specify specifically what value to use for the current in the calculation.
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I agree it's poorly worded. It does say maximum voltage drop which would be calculated by using the actual load.
 
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