NEC 220.82 interpretation

[Tainted]

NEC 220.82 says we can only use it on a 3-wire service or feeder conductors with ampacity of 100amp or greater.

Can we use NEC 220.82 demand calculation to calculate feeders and overcurrent protection on a 3-phase 4-wire non service dwelling unit?

 

[Dennis Alwon]

NEC 220.82 says we can only use it on a 3-wire service or feeder conductors with ampacity of 100amp or greater.

Can we use NEC 220.82 demand calculation to calculate feeders and overcurrent protection on a 3-phase 4-wire non service dwelling unit?

I am confused- you state that the code says only 3 wire service or feeder and you want to know if you can use 3phase 4 wire service for non-dwelling? The heading also states Dwelling Units..

I think you answered your own question... I would say "NO" you cannot.

220.82 Dwelling Unit.
(A) Feeder and Service Load. This section applies to a dwelling
unit having the total connected load served by a single
120/240-volt or 208Y/120-volt set of 3-wire service or feeder
conductors with an ampacity of 100 or greater. It shall be
permissible to calculate the feeder and service loads in accordance
with this section instead of the method specified in
Part III of this article.

 

[Tainted]

I am confused- you state that the code says only 3 wire service or feeder and you want to know if you can use 3phase 4 wire service for non-dwelling? The heading also states Dwelling Units..

I think you answered your own question... I would say "NO" you cannot.

The way I’m reading it is that you can use it for a 3-wire service but the apartment does not have a service conductors, it has a feeder so that’s why it says “or feeder conductors “

 

[Dennis Alwon]

The way I’m reading it is that you can use it for a 3-wire service but the apartment does not have a service conductors, it has a feeder so that’s why it says “or feeder conductors “

I agree but you were asking 3 phase and non dwelling. I agree that the equipment grounding conductor is not considered in the 3 wire setup for feeder

 

[Tainted]

I agree but you were asking 3 phase and non dwelling. I agree that the equipment grounding conductor is not considered in the 3 wire setup for feeder

Ooooh, no let me clarify:

Can we use NEC 220.82 demand calculation to calculate feeders and overcurrent protection on a 3-phase 4-wire dwelling unit feeder. This apartment is 4-wire non-service. It is just fed from regular 4-wire feeders.

 

[Dennis Alwon]

I see what's going on- I'm dense at times.... It's a good question but I believe you can use 220.82. Imo, this section could use some re-wording

 

[wwhitney]

NEC 220.82 says we can only use it on a 3-wire service or feeder conductors with ampacity of 100amp or greater.

Can we use NEC 220.82 demand calculation to calculate feeders and overcurrent protection on a 3-phase 4-wire non service dwelling unit?

If you're asking if the phrase "3-wire service or feeder" means "3-wire (service or feeder)" or means "(3-wire service) or feeder," then I would say the former is the standard meaning in English. The latter should be written as "feeder or 3-wire service" to avoid this ambiguity.

You have a 4-wire 3-phase feeder to a single dwelling unit? 220.84 for feeders/services for multiple dwelling units doesn't have the voltage system restriction of 220.82.

Cheers, Wayne

 

[jaggedben]

Ooooh, no let me clarify:

Can we use NEC 220.82 demand calculation to calculate feeders and overcurrent protection on a 3-phase 4-wire dwelling unit feeder.

No. 220.82 can only be used for a 3-wire circuit.

What Wayne said.

 

[JoeStillman]

I don't know of any utility that will serve a single-family home with 3Ø, 4W. Even the really big ones get 1Ø only.

 

[Fred B]

(2017NEC) 220.82 Dwelling Unit.
(A) Feeder and Service Load. This section applies to a dwelling
unit having the total connected load served by a single
120/240-volt (single phase) or 208Y/120-volt (3 phase) set of 3-wire service or feeder
conductors (neutral not counted into this see reference to 220.61 ) with an ampacity of 100 or greater. It shall be
permissible to calculate the feeder and service loads in accordance
with this section instead of the method specified in
Part III of this article. The calculated load shall be the result of
adding the loads from 220.82(B) and (C). Feeder and service entrance
conductors whose calculated load is determined by
this optional calculation shall be permitted to have the neutral
load determined by 220.61.

To me "feeder" as opposed to "service" would imply the required separation of N/G, and a total number of conductors even on single phase minimally 4 conductors. So if the wording limiting to 3 wire was literal counting the neutral, it could never be used in calculating "feeder" load.

IMO you could use this alternate method for 3 phase as long as all other required limitations are met.

 

[AlexKLMN]

Still confusing for me, Can we use NEC 220.82 for a 3-phase 4-wire dwelling unit feeder calculation?

 

[wwhitney]

Still confusing for me, Can we use NEC 220.82 for a 3-phase 4-wire dwelling unit feeder calculation?

The text specifies a "120/240-volt or 208Y/120-volt set of 3-wire" supply. So a single dwelling unit with a 208Y/120V 4 wire supply can't use 220.82.

Now if you have 3 dwelling units on a 208Y/120V 4-wire supply, which is further broken out as a balanced set of (3) 208Y/120V 3-wire supplies, each to one of the dwelling units, then you can use 220.82 for each of the individual dwelling unit feeders. And I would argue that you can sum those results for the 208Y/120V 4-wire supply, although that is not uncontested. But then you could also use 220.84 for the 208Y/120V 4-wire supply, which is the more typical option.

Cheers, Wayne

 

[AlexKLMN]

But the text also specifies "... or feeder with an ampacity of 100 or greater ".
Thank You!

 

[wwhitney]

But the text also specifies "... or feeder with an ampacity of 100 or greater ".

The parsing is

"a single (120/240-volt or 208Y/120-volt) set of 3-wire (service or feeder conductors) with an ampacity of 100 or greater."

So for 220.82 to apply, it must be (a) 120/240V or 208Y/120 (b) 3-wire (c) service or feeder conductors and (d) with an ampacity of 100A or greater.

Cheers, Wayne

 

[AlexKLMN]

The problem is that there is no 'and ' but it's only 'or' 100 Amp
So, I read it as 120/240 3-wire or 208/120 or 208/120 3-wire OR 100 Amp which means for me if it is 100 Amp I can use any system.
Probably because English is not my native language
Thank You!