Voltage Drop Issue

[SECofStL]

We are currently working on a project in St.Louis County. After we turned the building over to the owner, they began testing every receptacle for voltage drop. Keep in mind this is an office space with no sensitive equipment or motors. They are putting a 16A load on the receptacles and stating that every receptacle has a 10% voltage drop. The question is: To meet code, what amperage do you use to calculate the voltage drop of a branch circuit? Is it 180VA per receptacle, such as we have (5) receptacles on a circuit, at 180VA a piece, giving us a current of 4.3A? Or is it measured to the full capacity of the circuit, which they are 20A circuits.

 

[George Stolz]

There is no code. The test as described is not meaningful to the NEC.

 

[GoldDigger]

Such a test, or a similar requirement, might be part of contract specifications or part of a state energy code though.

 

[gadfly56]

The recommended max voltage drop is 5%, or 6 volts on a nominal 120 VAC system. See Mike Holt's comments at:

http://ecmweb.com/code-basics/dont-let-voltage-drop-get-your-system-down

As Mike notes, these are in the Fine Print Notes and are advisory only, unless your jurisdiction says otherwise.

That said, unless the contract called for maintaining a certain voltage drop, what's the problem?

 

[kwired]

OP indicated the owners are the ones that did this testing after occupying the building.

If contract documents didn't specify any particular level and there is no other building or energy codes requiring it, gladly offer to change it - for a price of course.:happyyes:

 

[ron]

Section 8.4 of ASHRAE 90.1, which is often the adopted energy code in jurisdictions has similar voltage drop criteria as the informational note in the NEC.

Because it is in an adopted energy code, it becomes mandatory.

It does not dictate what load the voltage drop needs to be calculated at. Most would accept using whatever was calculated in the panel schedules, which is often 180VA (120V @1.5A) per receptacle

 

[luckylerado]

...part of a state energy code....

Not Missouri.

As stated before, voltage drop of branch circuits is not an enforceable code. The current value used in the calculation should be the expected load.

You are looking at a #6 to pull off 3% using the #s you gave.

 

[ron]

Not Missouri.

Seems that it is https://www.energycodes.gov/adoption/states/missouri

 

[luckylerado]

Seems that it is https://www.energycodes.gov/adoption/states/missouri

There are no state wide adoption of energy codes in Missouri. I was not aware that Saint Louis County adopted this. Good call.

 

[david luchini]

Seems that it is https://www.energycodes.gov/adoption/states/missouri

The link says "Current Code - None Statewide."

 

[gadfly56]

Code smackdown!! Oooh, oooh, oooh!

 

[ron]

There are no state wide adoption of energy codes in Missouri. I was not aware that Saint Louis County adopted this. Good call.

You are right, I missed the indication that it was only some jurisdictions
https://energy.mo.gov/energy/communities/energy-codes

 

[Fitzdrew516]

The question is: To meet code, what amperage do you use to calculate the voltage drop of a branch circuit? Is it 180VA per receptacle, such as we have (5) receptacles on a circuit, at 180VA a piece, giving us a current of 4.3A? Or is it measured to the full capacity of the circuit, which they are 20A circuits.

If they are going to enforce energy code or have some other form of jurisdictional code adoption then the answer is: However many amps that circuit is drawing. This seems easy enough when it's a specified load such as a lighting circuit, a piece of equipment, etc. but when it is a "general receptacle" circuit I guess it gets a little trickier. Common sense tells me that you would use the 180VA per receptacle load that the NEC gives us. I think it's pretty stupid to assume full load on every recept like they are trying to do to you. Now, if the receptacle has a designated purpose such as a computer or something like that, then it is no longer a general receptacle and you should be calculating loads based off of whatever the receptacle is intended for.

Again, in my opinion you should be calculating voltage drop based on ((the # of receptacles * 180VA)/120) to get the amperage of the circuit. So for example - 5 recepts you's be calculating at 7.5A, 8 recepts would be 12A, and so on.

-Drew

 

[1964element]

Is it in EMT

Sent from my E6782 using Tapatalk

 

[iwire]

Not Missouri.

As stated before, voltage drop of branch circuits is not an enforceable code. The current value used in the calculation should be the expected load.

You are looking at a #6 to pull off 3% using the #s you gave.

A typical requirement per contract regardless of codes.

 

[1964element]

Look at prints anything over 85' wire size grows

Sent from my E6782 using Tapatalk

 

[luckylerado]

A typical requirement per contract regardless of codes.

This is pretty standard on jobs that we do without consideration of load. I think it is a crazy waste money in many cases and no one ever uses the real measured voltage in the calculation and the voltage rating of the equipment is always ignored as well. VD is the wild west in terms of understanding, implementation and enforcement.

 

[Michael15956]

This is pretty standard on jobs that we do without consideration of load. I think it is a crazy waste money in many cases and no one ever uses the real measured voltage in the calculation and the voltage rating of the equipment is always ignored as well. VD is the wild west in terms of understanding, implementation and enforcement.


View attachment 14092

How do you guys terminate that large wire at the receptacle?

 

[luckylerado]

How do you guys terminate that large wire at the receptacle?

Pigtail down to #12

 

[Michael15956]

Pigtail down to #12

What a pain!