Optional Residential Calc for Neutral & 4+ fixed appliances DF

[Finite10]

When calculating the NEUTRAL in the Optional residential method- I revert to the Standard method to size the neutral.

Do I reduce the '4 or more 120V fixed appliances' load by 75% ?


My CE text book is excellent but does not reduce the Demand Factor for these when calculating the neutral.
The Annex D examples in the NEC doesn't address this, too few fixed appliances.
Article 220.53, and of course 220.61, both seem like they'd apply, to me.

 

[Smart $]

I'm going to say no.

220.82(B)(3)a provides for demand reduction of those loads.

...and the non-excluded fixed appliances are not limited to 120V.

 

[Finite10]

Thank you for the help

Thank you for the help

Thanks S$
The reason I specified 120V was to let readers know I excluded 240V loads like Water Heater when calculating the Neutral.

As I read it, 220.82(B)(3) is applied to the Ungrounded conductors under Part 4 Optional Method.

I agree with you S$
200.82(A) last sentence:
"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"

It's silent about 220.53 which allows 75% reduced DF for 4+ fixed appliances. So, I guess - I don't reduce the Neutral DF as in the Standard method even though I'm supposed to use that method to calculate Neutral?

 

[Smart $]

...220.61"

It's silent about 220.53 which allows 75% reduced DF for 4+ fixed appliances. So, I guess - I don't reduce the Neutral DF as in the Standard method even though I'm supposed to use that method to calculate Neutral?

220.61 says,

(A) Basic Calculation. The feeder or service neutral load
shall be the maximum unbalance of the load determined by
this article. The maximum unbalanced load shall be the
maximum net calculated load between the neutral conductor
and any one ungrounded conductor.

I take that to mean the [maximum unbalanced] neutral load is determined using the same method used to determine the ungrounded conductor calculated load. The ungrounded conductor calculated load is determined by either the standard or optional method, and you cannot intermix the two methods unless specifically mentioned. An example of such is 220.84(B).

 

[Finite10]

Yep, that appears to be it.

220.82(A) specifically mentions 220.61 and doesn't mention 220.53.
It seems so obvious now.

Thanks a million for your time Smart $. I called the owner of the shop I started at in 1979 and even HE didn't know.

 

[HEYDOG]

I believe that you can use 220.53 for sizing the neutral even though you used the optional method for sizing the ungrounded conductors. There is no optional method for sizing the neutral so you have to use the standard method. If you used the standard method to start with you would be able to use 220.53. Just because your using the optional method does not mean the load has increased on the neutral. However you have to make sure the neutral is not smaller than required by 250.24(c)(1).

 

[Smart $]

I believe that you can use 220.53 for sizing the neutral even though you used the optional method for sizing the ungrounded conductors. There is no optional method for sizing the neutral so you have to use the standard method. If you used the standard method to start with you would be able to use 220.53. Just because your using the optional method does not mean the load has increased on the neutral. However you have to make sure the neutral is not smaller than required by 250.24(c)(1).

Let me put why you cannot use 220.53 in different words... :roll:

220.53 is part of the standard load calculation method under Part III of Article 220.

220.61 says, "The feeder or service neutral load shall be the maximum unbalance of the load determined by this article."

If the Optional Method of Article 220 Part IV is used to determine the load, then the result is "the load determined by this article" specified in 220.61.

 

[HEYDOG]

I agree with you 100%. That is exactly why I can use it. This is all part of article 220.

 

[Smart $]

I agree with you 100%. <---> That is exactly why I can use it. ...

Major contradiction

 

[HEYDOG]

Article 220 is just that an article. You stated that from 220.61 it says unbalance load as determined by this article. This implies article 220. Section 220.61 is not a article in itself. Look at the NEC style manual. 220.61 is a section of article 220.

 

[Smart $]

Article 220 is just that an article. You stated that from 220.61 it says unbalance load as determined by this article. This implies article 220. Section 220.61 is not a article in itself. Look at the NEC style manual. 220.61 is a section of article 220.

I am not in disagreement with what you write above. However, feeder and service loads determined by Article 220 are either per Parts III and V, or Parts IV and V. There is no crossing over between Parts III and IV calculation methods except for 220.61... and that is only because it is permitted in 220.82(A), which says in part...

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.

The load referred to in 220.61, namely the "load determined by this article", is the load determined under Article 220 Part IV. Please refer to Figure 220.1 and note 220.61 is depicted by itself rather than in Part III.

 

[HEYDOG]

I can see your perspective. But 220.82(b) is taking the first 10kva plus 40% of the remaining loads and then you add in the heat or a.c according to 220.82(C). This is including all of my straight 240 volt loads also. On these loads there is no neutral. The way I see the breakdown of the article 220.1 is simply stating that 220.61 deals specifically with neutral loads. When it states in 220.61 as calculated in this article. That is article 220. If it stated as in this section I would agree.

 

[HEYDOG]

One other thing that I would like to ask. If the load is exactly the same and I size the neutral by the standard method has the neutral load changed just because I am now using the optional method. There is no optional method for down sizing the neutral. I could just make it the same size as the ungrounded conductors with either method. But If I want to reduce it I have to go back and use the standard method.

 

[Smart $]

I can see your perspective. But 220.82(b) is taking the first 10kva plus 40% of the remaining loads and then you add in the heat or a.c according to 220.82(C). This is including all of my straight 240 volt loads also. On these loads there is no neutral. The way I see the breakdown of the article 220.1 is simply stating that 220.61 deals specifically with neutral loads. When it states in 220.61 as calculated in this article. That is article 220. If it stated as in this section I would agree.

One other thing that I would like to ask. If the load is exactly the same and I size the neutral by the standard method has the neutral load changed just because I am now using the optional method. There is no optional method for down sizing the neutral. I could just make it the same size as the ungrounded conductors with either method. But If I want to reduce it I have to go back and use the standard method.

And what if in using the standard calculation to determine neutral load, your 4 or more fixed appliances included 240V loads? How do you plan to separate those to determine the maximum unbalanced neutral load?

The way you do it in either method is to take the percentage of the one-line-to-neutral loads to the total calculated load under that part. For example, if you have 20kVA general under the optional method, then you'd have 10kVA plus 40% of the other 10kVA for 14kVA general load demand. If your one-line-to-neutral loads were 5kVA, that would be 25% of the 20kVA loads, and 25% of 14kVA would be 3.5kVA.

Also refer again to the last sentence of 220.82(A). 220.61 says the load as determined by this article... and 220.82(A) says where the load is determined by the optional method... meaning the optional method calculated load is to be used for 220.61 calculation.

 

[CONDUIT]

First off if you look at the nec style manual there is only one article in article 220. 220.61 is not an article nor is 220.82. I would not use the 240 volt loads when sizing the neutral. If I had less than four appliances that had a neutral (grounded conductor) 115 volts I would not use the 75% allowed in 220.53 I would use the nameplate rating. Using the optional method how are you going to calculate in for the neutral for the 120/240 volt appliances such as the electric range or electric clothes dryer. You state that you can not go back into othe parts of the article except 220.61. 220.61 then tells me to calculate neutral for ranges and dryers at 70% from table 220.55 and 220.54. Here again if you can show me that there are different articles within article 220 according to the NEC style manual you might sway me. Like I stated before I can use either the standard or the optional and size the neutral the same as the ungrounded conductors but if I want to reduce the neutral I going to use 220.61 and 220.55 and 220.54 and 220.53 if I have four or more appliances that have a neutral conductor (115 volts). If what you state is correct I would be interested in learning how to down size the neutral using the optional method. If you would show me an example for a single family dwelling I woul appreciate it. I am not being arrogant.It's just that I have not seen it done this way and would be interested in learning it. Thank you.

 

[gndrod]

When calculating the NEUTRAL in the Optional residential method- I revert to the Standard method to size the neutral.

Do I reduce the '4 or more 120V fixed appliances' load by 75% ?


My CE text book is excellent but does not reduce the Demand Factor for these when calculating the neutral.
The Annex D examples in the NEC doesn't address this, too few fixed appliances.
Article 220.53, and of course 220.61, both seem like they'd apply, to me.

Hi Finite,
Article 220 can be confusing when calculating the unbalanced appliances unless each Section is adjusted within the method being used. Standard and optional methods are not intermixed as Smart$ mentions, so [220.61] is used for both methods in calculating the neutral size separately.

In using the standard method, the [220.53] 75% load DF is applied to 4 or more FIP Appliances (other than range, cl. dryers, space heating or A/C). The 3 or less FIP will be 100% NPR applied. The total FIP % used will be added to the General, SA, and Laundry subtotals prior to including CL.Dryer [220.54], range[220.55], elec. heat , A/C (omit smaller load if both used) and finally, 25% largest motor before totaling all for the dwelling standard total demand load.

In using the optional method(s), General, SA, and Laundry are totaled with All FIP, specific circuits, motors, etc. [220.82b3], [220.82b4] at the NPR only...before calculating the [220.80b] DF. Heating or A/C are not included here, but separately calculated in the [220.82c] subtotal prior to the final dwelling optional demand load total.

[220.61a] Standard calculation is then used to determine the unbalanced calculated load for the neutral conductor size.

I find this makes the [220] calculations easier to follow when deciding which method is more appropriate in considering a service size capacity with load averaging DF calculations.

 

[Smart $]

...

[220.61a] Standard calculation is then used to determine the unbalanced calculated load for the neutral conductor size.

...

Strike Standard calculation. Whichever method, standard or optional, is used to calculate load is also used to calculate maximum unbalanced neutral load. Just because 220.61 is in Part III does not mean Part III method is used to determine the maximum unbalanced neutral load.

 

[gndrod]

Strike Standard calculation. Whichever method, standard or optional, is used to calculate load is also used to calculate maximum unbalanced neutral load. Just because 220.61 is in Part III does not mean Part III method is used to determine the maximum unbalanced neutral load.

My whoops, the intent was 220.61 is a standard application to both methods.

 

[CONDUIT]

Smart $. I am heydog from my main office and conduit at my work office. I ask again if you can show me a sample dwelling unit calculation using the optional method for sizing the neutral if you downsize it. Also please tell me how many article's are in article 220. Thank you.

 

[Smart $]

Smart $. I am heydog from my main office and conduit at my work office. I ask again if you can show me a sample dwelling unit calculation using the optional method for sizing the neutral if you downsize it. Also please tell me how many article's are in article 220. Thank you.

I typically do not do calc's, let alone dwelling unit ones... so give me numbers, i.e. sq footage, loads, and such to work with... or better yet... you provide a full standard calc for the one you want me to do the optional method for.

Do you mean how many Articles are in Article 220... or how many articles?

Merriam-Webster Collegiate? Dictionary Browse

1ar?ti?cle
Pronunciation: '?r-ti-kəl
Function: noun
Etymology: Middle English, from Anglo-French, from Latin articulus joint, division, diminutive of artus joint, limb; akin to Greek arariskein to fit ― more at ARM
Date: 13th century

1 a : a distinct often numbered section of a writing b : a separate clause c : a stipulation in a document (as a contract or a creed) <articles of indenture> d : a nonfictional prose composition usually forming an independent part of a publication (as a magazine)
2 : an item of business : MATTER
3 : any of a small set of words or affixes (as a, an, and the) used with nouns to limit or give definiteness to the application
4 : a member of a class of things especially : an item of goods <articles of value>
5 : a thing or person of a particular and distinctive kind or class <the genuine article>

x
2article
Function: transitive verb
Inflected Form: -cled ; -cling \-k(ə-)liŋ\
Date: 1820

: to bind by articles (as of apprenticeship)

x
article of faith

15th century
: a basic belief



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Note 220.61 uses the word "article" and not "Article".