Voltage drop

[liqababy]

Could someone please help me out with a situation I have encountered. I have a large residential (dwelling) design i am working on. When i do the NEC calculation for the load i get 167A, so based on local service sizes requirements that would be a 200A service. However, this residence is 450 feet away from the service entrance. Could someone quote me the requirements from the NEC what should i use to calculate the voltage drop? Should i use the 167A NEC calculated load or should i use the 200A service size for my calculation of the voltage drop.

This is for a 200A, 120/240V single phase system. I want to know if at 450 feet would it be adequate to use 350MCM copper conductor and should i use 167A (NEC calculated) or 200A (Service size) to calculate the voltage drop?

 

[Dsg319]

You’ll get mixed opinions. IMO the calculated load is more than enough to punch into your calcs.

 

[liqababy]

that's why i was also wondering if there were any NEC, or basically any other code, references related to this. But all i found is that NEC says maximum of 3%. Expert opinions are great but expert opinions backed with code is better

 

[roger]

The NEC only recommends a maximum VD, it doesn't mandate anything. I work on single phase systems that range from 229V to 253V so whatever you do won't work across the board.

 

[LarryFine]

Welcome to the forum.

Voltage drop is dependent on actual current and circuit impedance.

Thus, use the calculated load, which will probably never be seen.

 

[electrofelon]

Actual peak load will probably never exceed half of that calculated value. I used to use about 60 amps for a dwelling for VD purposes. I have bumped that up to 80-90 amps now with The increased likelihood of EV chargers and more electric stuff. I would probably use 250 or 350 Aluminum. No way I would use copper, unless someone had an excess money problem and really begged me to help them get rid of it.

 

[electrofelon]

IMO, of it was my money, I would stick with AL conductors, but would use a 320 base and use compression lugs, and a true panel board (also with compression lugs) instead of a load center type panelboard. You get a much better installation with more benefits and a cheaper price over using copper.

 

[tortuga]

If your really in Belize they go by the 2018 CARICOM Regional Energy Efficiency Building Code
If you refer to section C405.9 Voltage Drop in Feeders and Branch Circuits it says:

The total voltage drop across the combination of feeders and branch circuits shall not exceed 5 percent.

The system voltage used in the calculation is your nominal voltage either from NEC 220.5 or standard regional voltages south of the US like 127/220 or 416/240, you use the calculated load less any continuous factors you may have added.

 

[kwired]

Though you likely seldom if ever see the 167A of calculated load you may want to consider that starting of the AC compressor(s) or other larger motor loads if you have them may still cause significant voltage drop even though briefly. I'd probably consider parallel 4/0 aluminum for supply conductors with that long of a run or at least bury a spare conduit and the customer can thank you later when they decide to pull the extra set of conductors through it.