voltage drop

[tommy]

Can I get example on how and when to use 3% and the 5% for VD

 

[RUWired]

Can I get example on how and when to use 3% and the 5% for VD

One example would be if you installed a sub panel and had branch circuits from that , you should keep the voltage drop from the main panel to the last device or equipment to 5% total.Example would be 2% for the feeder to the sub panel and 3% the the device or equipment.Most of the time as electricians, we try to keep the VD to 3% with the branch wiring and don't think of the feeder.
Rick

 

[tommy]

So if I was installing just the main feeder I would use What? ( 1%thru to 5% mychoice?

 

[Dennis Alwon]

So if I was installing just the main feeder I would use What? ( 1%thru to 5% mychoice?

3%--- --------

 

[Dennis Alwon]

3%--- --------

Ruwired got it right. If you run a feeder you calculate the VD at 3%. We generally never calculate the VD from the feeder thru the branch circuit. Normally we would do the feeder at 3% and then the branch circuits at 3%. Technically you should do the feeder plus the branch circuit at 5%

 

[tommy]

Thanks I understand now. I've been doing it right.5% overall 3% in between

 

[Snorks]

This is true only if you are not using Title 24 specifications. Then it is up to the particular spec that is utilized in your area or state.
Title 24 refers to Energy Efficient specifications and always have lesser VD allowances.

 

[W6SJK]

Title 24 refers to Energy Efficient specifications and always have lesser VD allowances.

Huh? Where do the Appliance Efficiency Regulations or Title 24 Part 6 limit voltage drop?

 

[George Stolz]

Tommy, an item that hasn't been mentioned is that voltage drop is not a mandatory consideration under the NEC. Check out the FAQ for more info on that aspect.

That said, I agree with the above members who've said that 5% total, between the service and the outlet is a well-designed system in most cases.

In general, a rule of thumb that doesn't do too bad is branch circuits over 100' in length should be examined, and generally kicked up a size or two.

 

[tommy]

George why do think its not required.I agree FPN is not enforcible, But why have it there?Just curious on any thoughts.Maybe should be required,maybe too hard to inspect or something

 

[George Stolz]

George why do think its not required.I agree FPN is not enforcible, But why have it there?Just curious on any thoughts.Maybe should be required,maybe too hard to inspect or something

Check out this proposal to the 2008 NEC:

2-277 Log #2837 NEC-P02 Final Action: Reject

(215.2(A)(3), FPN 2)
______________________________________________________________
Submitter: Robert P. McGann, City of Cambridge

Recommendation: Make this Fine Print Note into mandatory text.

Substantiation: This is necessary to properly facilitate the operation of overcurrent protection. We are all looking at ways to reduce the number of electrical fires. This will aid us in achieving that goal.

Panel Meeting Action: Reject

Panel Statement: Acceptable voltage drop is a system design issue that may vary with the application and equipment involved.

Number Eligible to Vote: 12
Ballot Results: Affirmative: 12​

It's a design issue. Some equipment is not as badly affected by voltage drop as others.

It's difficult to create a safety issue out of voltage drop, IMO.

Take a look at 90.1(B), too. A code compliant system is not necessarily snazzy, just safe. ​