overcurrent device

[jumper]

should not we go down when ampacity over 800

If you mean use a 800A breaker, then the answer is no.

You pick conductors large enough for the load and the breaker size.

 

[iwire]

Why did you choose to stop before the example is complete? :?

It is obvious you and I are not going to agree on this.

If an inspector asks me what is the calculated load and I tell him 156 amps, he expects, and I will be giving him a complete calculation that includes the continuous and non-continuous loads. So if I tell him 156 he knows I need at least 156 amps worth of OCPD and conductor.

I have no idea why anyone would provide a 'service calculation' without including both the continuous and non-continuous loads. It makes no sense and as you have pointed out would not be meaningful in any way.

 

[iwire]

If you mean use a 800A breaker, then the answer is no.

You pick conductors large enough for the load and the breaker size.

Don't forget 800 amps and under the conductors can be sized less than the OCPD.

 

[david luchini]

Why did you choose to stop before the example is complete? :?

It is obvious you and I are not going to agree on this.

If an inspector asks me what is the calculated load and I tell him 156 amps, he expects, and I will be giving him a complete calculation that includes the continuous and non-continuous loads. So if I tell him 156 he knows I need at least 156 amps worth of OCPD and conductor.

I have no idea why anyone would provide a 'service calculation' without including both the continuous and non-continuous loads. It makes no sense and as you have pointed out would not be meaningful in anyway.

I didn't stop before the example was complete, I reviewed it completely in post #16. However, the calculated load is given in the very first part of the example. It is 28,400 VA.

I would expect a service load calculation (or a feeder load calculation) to be done in accordance with 220.40. It says

The calculated load of a feeder or service shall not be less than the sum of the loads on the branch circuits supplied, as determined by Part II of this article, after any applicable demand factors permitted by Parts III or IV or required by Part V have been applied.

As you can see, there is nothing about continuous or non-continuous, or about 125%. Which is why I indicated in post 5 that the question did not have enough information to answer properly.

However, including the 125% in the load calculations does you no good either. For instance, go back to the feeder for the 80A lighting load. Let's say we included the 125% for the inspector so the "calculated load" is 100A, and you need a min. 100A c/b and #3 feeder. But if the feeder was #3 THHN and it was run in a 105 deg F ambient. The adjusted ambient of #3 THHN in 105 degrees is 95.7. Per 215.2(A)(1), you would not be able to use #3 and would have to increase the feeder to #2, because the ampacity of the #3 (95.7) is less than the calculated load (100A.) However, if the calculated load is 80A (as it should be from Art 220.) then the #3 feeder would be fine in the higher ambient.

The code tells you how to do load calculations in Art 220, and how to size feeders and feeder overcurrent protection (using the 125% of continuous) in Art 215. If the 125% continuous factor was meant to be part of the "load calculation," then the Code would have included it in Art 220.

 

[Dennis Alwon]

I agree with David. Suppose you have a warehouse with lighting only. Loads are continuous but when we calculate we use VA/ sq. ft or we can calculate the actual load of the lights if it is more than the va/sq.ft.

Suppose the load was 840 amps of lights. Where in that calculation is the 125%. If all the loads are continuous it would appear you need to calculate the service at 125% or the breaker would have to be rated 100% usage. Yes???

 

[iwire]

Where in that calculation is the 125%.

It is not there until we include it, just like any part of a load calculation.


If you have not included the 125% for continuous loads you are not done calculating are you?

And if you are not done with the calculations why would you present it as the 'service calculation'? :huh::?

 

[iwire]

If the 125% continuous factor was meant to be part of the "load calculation," then the Code would have included it in Art 220.

We are going to have to remain in disagreement.

 

[Dennis Alwon]

I see what you are saying Bob and I think you may be correct. Example D3 separates the continuous loads from non continuous loads and it does do the 125% of the continuous loads at the end of the example. So in fact it is in the calculation.

 

[david luchini]

It is not there until we include it, just like any part of a load calculation.

But what tells you to include it in the load calculation? The Code certainly doesn't.

The Code tells you that the service load calculation is the sum of the branch circuit loads after any demand factors have been applied. That is to say add up all of the branch circuit loads and apply any applicable demand factors. That's it. That's the end of the load Calculation as far as the Code is concerned. Why would I keep going on a load calculation if I've reached the end? There is nothing about 125%, nothing about 80%, nothing about continuous, nothing about non-continuous. You are trying to apply factors which have nothing to do with the load Calculation into the load Calculation.

Now when I want to size my feeders or service conductors, I need to take continuous vs. non-continuous into account, but not before then. As I mentioned, applying a "continuous load" factor into your load calculation my cause you to need feeders larger than are required by code. This will not cause an unsafe condition, but it would be costing a client more than needed.

 

[Dennis Alwon]

It does seem odd that 220 does not state to use 125% of the continuous load however

230.42 Minimum Size and Rating.
(A) General. The ampacity of the service-entrance conductors before the application of any adjustment or correctionfactors shall not be less than either 230.42(A)(1) or (A)(2). Loads shall be determined in accordance with Part III, IV, or V of Article 220, as applicable. Ampacity shall be determined from 310.15. The maximum allowable current of busways shall be that value for which the busway has been listed or labeled.


(1) The sum of the noncontinuous loads plus 125 percent of continuous loads
Exception: Grounded conductors that are not connected to an overcurrent device shall be permitted to be sized at 100 percent of the continuous and noncontinuous load.


(2) The sum of the noncontinuous load plus the continuous load if the service-entrance conductors terminate in an overcurrent device where both the overcurrent device and its assembly are listed for operation at 100 percent of their rating

 

[GoldDigger]

It does seem odd that 220 does not state to use 125% of the continuous load however

Some of the calculations in the code specifically state that what is being calculated is "load." Other calculations state that what is being calculated is the minimum ampacity of the conductors and the minimum rating for the OCPD. The sections which multiply by 125% to get required ampacities do not explicitly state that the same multipliers should be applied to the "load" numbers.

So, as I see it, part of the problem is in the just what is being calculated. 220.40 referers to 430 for calculations for motors. 220.14 in Part I states:

C) Motor Loads. Outlets for motor loads shall be calculated in accordance with the requirements in 430.22, 430.24, and 440.6.

Does or does not this require the inclusion of the 125% factor in those calculations in cases where 430.2x requires a 125% factor in the ampacity calculation?

If the 220.40 numbers include any applicable 125% factors (and I think that most will agree that the numbers should include the diversity and multi-motor circuit factors in 430), then 430.42 would seem to be applying the same 125% factor a second time. But this, I think, may be related to the observation from another thread that motor loads are not classified as continuous or non-continuous, since that is assumed to already be part of the calculation.

And then 430.42 adds to the confusion by treating "load" and "current carrying capability" as being identical, or at least one being in a relationship to the other which depends for conversion only on the nominal voltage. But it explicitly introduces a 125% factor.

At this point, I withdraw from the discussion in complete confusion.

 

[jumper]

Don't forget 800 amps and under the conductors can be sized less than the OCPD.

Yep .I know. Thanks

The OP is gonna be lost in this thread.

 

[Dennis Alwon]

At this point, I withdraw from the discussion in complete confusion.

Chicken........

 

[jumper]

It does seem odd that 220 does not state to use 125% of the continuous load however

It is just typical of the way the darn NEC is set up, no one section gives you all the info one needs to do some thing.

 

[jumper]

Bob and David are actually both correct.

David is correct that the load calculation according to 220 does not factor in continuous loads. He does it later.

Bob is correct that one is not truely finished because one needs to factor in continuous loads in order to size the conductors and OCPD. He does it as he figures the loads.

The example in Annex D(3) is flawed because the of the note regarding lighting. The connected load was smaller than the load required by the table, so the largest is chosen regardless of the fact that it will be continuous.

Whether one does it as David does or how Bob does is irrelevant really, you are going to factor it in at some point.

 

[ActionDave]

Bob and David are actually both correct.

David is correct that the load calculation according to 220 does not factor in continuous loads. He does it later.

Bob is correct that one is not truely finished because one needs to factor in continuous loads in order to size the conductors and OCPD. He does it as he figures the loads.

The example in Annex D(3) is flawed because the of the note regarding lighting. The connected load was smaller than the load required by the table, so the largest is chosen regardless of the fact that it will be continuous.

Whether one does it as David does or how Bob does is irrelevant really, you are going to factor it in at some point.

You bring a whole new meaning to the term "Moderator" and I think you nailed it. That and what you said in the post before. A stronger word than "darn" would be fitting but not appropriate.

 

[iwire]

Hey,I just want to point out I had said pretty much the same thing as jumper in my post 15.

Also instead of just arguing the points I just said we disagree on things and left it at that.

I can't get much more moderate than that.

 

[ActionDave]

Hey,I just want to point out I had said pretty much the same thing as jumper in my post 15.

Also instead of just arguing the points I just said we disagree on things and left it at that.

I can't get much more moderate than that.

You are more moderate than you get credit for. :lol: (really, you are. And I skim read just as much as anybody)

 

[jumper]

Hey,I just want to point out I had said pretty much the same thing as jumper in my post 15.

Also instead of just arguing the points I just said we disagree on things and left it at that.

I can't get much more moderate than that.

I learned to do it as you did in trade school, but Charlie b and I have argued this point and that example more than once.

And yes you are moderate...............even fer a Yankee.

I really wish the CMP would fix that example.

 

[iwire]

And yes you are moderate...............even fer a Yankee.

:thumbsup: