Demand loads non-continuous?

[cppoly]

For lighting loads subject to the demand factors in table 220.42, are these considered non-continuous loads?

 

[charlie b]

I would say yes. It makes no sense to me to add 25% for the load being continuous, then reducing the load by the demand factors in that table.

 

[mwm1752]

220.42 is not applicable to specific branch circuits & whether loads are continuous or not. I have yet to see an actual lamp wattage total used with this formula not really sure if it applies that way -- generally we find the lighting load demand application determined from sq ft of specific occupancies per table 220.12 -- apparently a 3000sq ft dwelling is more likely to have a greater percentage of its lighting load energized at the same time than 120,000 sq ft dwelling.

 

[Smart $]

For lighting loads subject to the demand factors in table 220.42, are these considered non-continuous loads?

Yes and no. IOW, it applies to both continuous and non-continuous. In my profound wisdom lol, I have rationalized factoring applies to the continuous portion first, i.e top down.

re: extra 25% for continuous loads... not part of Article 220 calculations. Article 220 loads are calculated prior to size and rating determination.

 

[resistance]

What Charlie said.

 

[cppoly]

Thanks. This makes sense. I couldn't find any where in the code where it talks about feeder demand loads being continuous or not.

 

[fmtjfw]

For lighting loads subject to the demand factors in table 220.42, are these considered non-continuous loads?

Lighting basically everywhere but residential (dwelling, motel, dormitory) is considered a continuous load.

Examples: Schools, Offices, Retail, since it is very likely to be on more than 3 hours in a row.

 

[cppoly]

Lighting basically everywhere but residential (dwelling, motel, dormitory) is considered a continuous load.

Examples: Schools, Offices, Retail, since it is very likely to be on more than 3 hours in a row.

Here's what gets me though. Take a multi story residential building for example that allows a demand factor to be applied to the feeders. I can see how a certain percentage of people will not have their lights on but it's also true that a certain percentage will have their lights on and it will be a continuous load. Somehow it works out you can take a massive demand factor of .25 for anything over 120,000 VA.

 

[resistance]

Somehow it works out you can take a massive demand factor of .25 for anything over 120,000 VA.

Explain?

 

[cppoly]

Explain?

I mean if you assume that the lighting demand loads for feeders are non-continuous after application of the demand factors in table 220.42, it still manages to work (not have any problems) if you follow the table. For dwelling units, a general lighting load over 120,000 VA can apply a 25% demand factor to it.

 

[mwm1752]

When service calculations are done to size service you are not going to multiply the answer by 125%. if your calculations equal say, 190amps then a 200 amp service will be sufficient for the structure.

 

[cppoly]

When service calculations are done to size service you are not going to multiply the answer by 125%. if your calculations equal say, 190amps then a 200 amp service will be sufficient for the structure.

What about for the purposes of circuit breaker and conductor sizing?

 

[david luchini]

What about for the purposes of circuit breaker and conductor sizing?

The ampacity of your service conductors must be sized for not less than the sum of the noncontinuous loads plus 125% of the continuous loads (unless your service OCPD is 100% rated.) - See 230.42.

It is up to you to determine which loads are continuous (per the definintion in Art. 100.) The Code does not direct you on which specific loads are continuous.

 

[mwm1752]

What about for the purposes of circuit breaker and conductor sizing?

Your original question seems to deal with service calculations -- I was pointing out the calculation is the max amperage anticipated for the service therefore there is no more adjustments for continuous or non continouos loads needed

 

[Smart $]

Your original question seems to deal with service calculations -- I was pointing out the calculation is the max amperage anticipated for the service therefore there is no more adjustments for continuous or non continouos loads needed

That is correct... as far as calculations per Article 220.

However, when you determine your minimum ocpd rating* under 215.3 and minimum conductor size under 230.42(A)(1) or 215.2(A)(1), you have to multiply the continuous portion of the load by 125%. As such, you have to segregate your continuous and noncontinuous loads throughout your Article 220 calculations.

* Service ocpd is determined indirectly based on conductor ampacity and a maximum rating rather than minimum rating.

 

[resistance]

I mean if you assume that the lighting demand loads for feeders are non-continuous after application of the demand factors in table 220.42, it still manages to work (not have any problems) if you follow the table. For dwelling units, a general lighting load over 120,000 VA can apply a 25% demand factor to it.

Not sure I can agree with what you said fully. It may be your wording. Its the remainder over 120K thats allowed to use the 25% demand factor. Don?t get your point either, as you can also use an additional demand of 35%?why pinpoint the 25% only.

 

[cppoly]

Not sure I can agree with what you said fully. It may be your wording. Its the remainder over 120K thats allowed to use the 25% demand factor. Don?t get your point either, as you can also use an additional demand of 35%?why pinpoint the 25% only.

I was highlighting the 25% for anything over 120,000 VA to indicate that the code assumes 75% of the load above 120,000 VA is considered to be off at any given moment. For the 25% of the lighting that is assumed to be on, I would assume this is considered a continuous load though.

This would affect equipment buss ratings too right? Even though a final calculated load is determined to be let?s say 1,180 A with demand, is this entire load considered non-continuous so that a 1,200 A main distribution board can be put in or would the rating need to be higher to account for the continuous loads?

 

[Smart $]

I was highlighting the 25% for anything over 120,000 VA to indicate that the code assumes 75% of the load above 120,000 VA is considered to be off at any given moment. For the 25% of the lighting that is assumed to be on, I would assume this is considered a continuous load though.

This would affect equipment buss ratings too right? Even though a final calculated load is determined to be let?s say 1,180 A with demand, is this entire load considered non-continuous so that a 1,200 A main distribution board can be put in or would the rating need to be higher to account for the continuous loads?

As I said earlier, load calculations under Article 220 make no consideration for continuous vs. non-continuous. Factoring loads at 125% falls under Articles 210, 215, 230, and other pertinent articles.

PS: As I also said earlier, apply demand factoring to continuous loads first. It's not written in Code, but a logical conclusion on my part.

 

[fmtjfw]

I was highlighting the 25% for anything over 120,000 VA to indicate that the code assumes 75% of the load above 120,000 VA is considered to be off at any given moment. For the 25% of the lighting that is assumed to be on, I would assume this is considered a continuous load though.

This would affect equipment buss ratings too right? Even though a final calculated load is determined to be let?s say 1,180 A with demand, is this entire load considered non-continuous so that a 1,200 A main distribution board can be put in or would the rating need to be higher to account for the continuous loads?

When you are designing a circuit to feed lighting that is on more than 3 hours in a row, you treat it as a continuous load, with 80%/125% rule for the conductors and the OCPD.