Red tagged for voltage drop what gives? (NY)

[hbiss]

Did the inspector actually perform the VD calculation and tell you that the condcutors were too small?

In this instance it was just one run. What do they do in a large and complicated facility? I can see this going nowhere.

-Hal

 

[retirede]

The International Energy Conservation Code has been a statewide requirement in Illinois for almost 20 years, yet most smaller electrical contractors act like they have never heard of it.

I don’t think they’re acting! At least the ones around here aren’t.

 

[gene6]

whenever I do VD calcs, it's based on the connected load. Has not been challenged by reviewers (yet)

The inspector was back out today and he said exactly that "the article 220 calculated load" is used.

 

[electrofelon]

The inspector was back out today and he said exactly that "the article 220 calculated load" is used.

Great, size the wire on average 2.5 times larger than it needs to be....and I thought the NFPA and their CMP's were bad......

 

[Hv&Lv]

I would like to see the constants he used for the formula.
5% of 120 is less than 5% of 124.
did he use nominal or delivered voltage?
I understand NEC says 120 nominal, but they aren’t enforcing NEC. It’s some other code. Does that code specify nominal will be used for calculations?
how far did you miss the mark? Who did the calculations of connected load? Was it on a print or off the top of his head..

Its not really important, and I’ll never wire in NY, I’m just curious..

 

[paulengr]

The inspector was back out today and he said exactly that "the article 220 calculated load" is used.

That doesn’t work. Ask 3 electricians for an article 220 load and you will get 3 answers. Just the standard and alternative method are bad enough. Now if we look at commercial then there are no automatic diversity factors.

 

[Tulsa Electrician]

It's nice to see some talk about VD.

 

[nizak]

It's nice to see some talk about VD.

 

[nizak]

I’ve got a storage unit that’s got 1 GFCI receptacle and one keyless fixture.

Was running my small table saw one day and noticed the slow start and considerable dimming light.

Put a meter on it and it was hovering around 105V running. Start up was ridiculous.

 

[ron]

I’ve got a storage unit that’s got 1 GFCI receptacle and one keyless fixture.

Was running my small table saw one day and noticed the slow start and considerable dimming light.

Put a meter on it and it was hovering around 105V running. Start up was ridiculous.

You are making the assumption that the service voltage was being provided at the time of use was at nominal 120V.

At that time, the service may have been running low, which does not affect the voltage drop calculations that are being discussed, which are only based on the nominal voltage. A voltage drop calc may be fine in your situation because the calculated load is low.

 

[infinity]

without a consistent methodology to determine VD just how are they planning to enforce this?

Yes he uses an app.

As Bob mentioned VD calculations can be all over the place. You can use a variety of apps with different results. If the intention of the state is to enforce these calculations by using an app then they should formally adopt a specific app so everyone is on the same page.

 

[gene6]

I would like to see the constants he used for the formula.
5% of 120 is less than 5% of 124.
did he use nominal or delivered voltage?
I understand NEC says 120 nominal, but they aren’t enforcing NEC. It’s some other code. Does that code specify nominal will be used for calculations?

He used NEC the article 220 'calculated load', and the nominal voltages are from 220.5.
I will admit I have not done a voltage drop calculation in like 30 years and am fuzzy on the other variables.
There are some great old threads on here on VD.
My apprentice has a app on her phone that does VD calcs, its sponsored by one of the major wire manufacturers.

That doesn’t work. Ask 3 electricians for an article 220 load and you will get 3 answers.

The answer that this AHJ accepts as correct is then used for his voltage drop calc LOL.

If the intention of the state is to enforce these calculations by using an app then they should formally adopt a specific app so everyone is on the same page.

I should have been more clear, he said it does not have to be on an app. I was saying he uses an app to do it. He started showing me the app and I tuned out as I am pretty rusty on that stuff, used to engineered jobs.
My voltage drop app is my gut instinct, and I honestly felt the run was a little long so I had no fight in me for it.

 

[hbiss]

I will admit I have not done a voltage drop calculation in like 30 years and am fuzzy on the other variables.

It couldn't be simpler. With the motor or equipment running, measure the voltage at the beginning of the run then measure the voltage at the motor or equipment. Subtract one number from the other to see your voltage drop. Then you can take that number and the voltage at the beginning of the run to figure a percentage.

The problem with what this guy is doing is no readings are taken. That's OK for a ballpark number if you are designing the system, but if you are being held to an exact do not exceed number or face a violation and extra work, actual calculations using real numbers is the only legal way.

-Hal

 

[petersonra]

The problem with what this guy is doing is no readings are taken. That's OK for a ballpark number if you are designing the system, but if you are being held to an exact do not exceed number or face a violation and extra work, actual calculations using real numbers is the only legal way.

-Hal

What code or rule requires this?

 

[dkidd]

See post 2.

 

[petersonra]

See post 2.

I was referring to actual field measurements of voltage drop as suggested in post 33.

 

[Tulsa Electrician]

I would love to see what he did.
Can you duplicate his numbers using his app.
Did he make increase the EGC as well?

 

[Hv&Lv]

What code or rule requires this?

C405.9 Voltage Drop in Feeders and Branch Circuits

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

The code doesn’t say calculated voltage drop. It says voltage drop. Which means actual voltage drop

 

[hbiss]

I was referring to actual field measurements of voltage drop as suggested in post 33.

Wouldn't that be the only way to accurately determine what the number is? Anything else is just an approximation- which is normally fine, except now you have an AHJ holding you to 5% or less and the approximation method could be off by a few percent causing you to do extra work. So, as far as I'm concerned if you have somebody holding a gun to your head over this somebody has to prove who is right.

-Hal

 

[Phil Timmons]

Here comes some more SKM or ETAP work . . . .

Sort of like the Arc Flash Labeling was the (EE / Electrician) Full Employment Act. ;P