2014 Code... 210.19(A)(1)a or b

Status
Not open for further replies.
This change was made for services, feeders and branch circuits, but it seems to me that the code making panels don't really understand conductor ampacity. The actual ampacity of a conductor is the maximum amount of current that the conductor can carry under the conditions of use. The correction factors and adjustment factors are conditions of use. The code ampacity of any conductor is the value you have after you apply the correction and adjustment factors.

List item (a) will always be larger.

I know that this is not what they were really trying to say, but it is what the words say.

Ampacity. The maximum current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating.
Click to expand...
 
don_resqcapt19 said:
This change was made for services, feeders and branch circuits, but it seems to me that the code making panels don't really understand conductor ampacity. The actual ampacity of a conductor is the maximum amount of current that the conductor can carry under the conditions of use. The correction factors and adjustment factors are conditions of use. The code ampacity of any conductor is the value you have after you apply the correction and adjustment factors.

List item (a) will always be larger.

I know that this is not what they were really trying to say, but it is what the words say.
Click to expand...

When using list item (b), would you use the ampacity of the load or the ampacity of load as a continuous load?
 
With (b) you use the actual load.

The intent of the rule is for (a) you use the non-continuous load plus 125% of continuous load and size the conductor based only on the values in the ampacity table.

The intent of (b) is to have a conductor that has an ampacity that is at least equal to the continuous plus the non-continuous load after you have applied any correction and or adjustment factors to the conductor's table ampacity.

However because of the definition of the term ampacity, that is not what the rule really says. The term "ampacity" means that the correction and/or adjustment factors have been applied to the table ampacity values. To make the rule say what they want it to say, they have to specify the use of the table values for (a).
 
don_resqcapt19 said:
With (b) you use the actual load.

The intent of the rule is for (a) you use the non-continuous load plus 125% of continuous load and size the conductor based only on the values in the ampacity table.

The intent of (b) is to have a conductor that has an ampacity that is at least equal to the continuous plus the non-continuous load after you have applied any correction and or adjustment factors to the conductor's table ampacity.

However because of the definition of the term ampacity, that is not what the rule really says. The term "ampacity" means that the correction and/or adjustment factors have been applied to the table ampacity values. To make the rule say what they want it to say, they have to specify the use of the table values for (a).
Click to expand...
Thank you don. You summed this up better than any articles I have read about this so far.
 
don_resqcapt19 said:
...

The intent of the rule is for (a) you use the non-continuous load plus 125% of continuous load and size the conductor based only on the values in the ampacity table.

...
Click to expand...
I believe the intent of (a) is sizing for selection and coordination with 110.14(C) temperature limitations.

The intent of (b) is to select the minimum conductor size that has an ampacity, after the application of adjustment and correction factors, not less than the calculated load.

I had a Public Input all written up and submitted for 210 and 215 (forgot about 230). I was reviewing them and decided to make some modifications... then decided not to. I didn't see a 'cancel' option, so I thought exiting would not save the modification. When I exited, a dialog asked if I wanted to save the modifications I made (at least that's what it appeared to ask), I selected no (or the closest option to no), and both submitted Public Inputs got deleted... :slaphead::rant:

I have yet to muster the initiative to re-write them... :(
 
don_resqcapt19 said:
With (b) you use the actual load.

The intent of the rule is for (a) you use the non-continuous load plus 125% of continuous load and size the conductor based only on the values in the ampacity table.

The intent of (b) is to have a conductor that has an ampacity that is at least equal to the continuous plus the non-continuous load after you have applied any correction and or adjustment factors to the conductor's table ampacity.

However because of the definition of the term ampacity, that is not what the rule really says. The term "ampacity" means that the correction and/or adjustment factors have been applied to the table ampacity values. To make the rule say what they want it to say, they have to specify the use of the table values for (a).
Click to expand...

if I just use the actual load, for list item B... isnt it possible to come up with an ampacity that is less than the continuous Load?
 
xformer said:
if I just use the actual load, for list item B... isnt it possible to come up with an ampacity that is less than the continuous Load?
Click to expand...
No, you will have an ampacity that is equal to the actual connected load. You are just eliminating the 25% adder that is normally applied to continuous loads.
 
My problem with this revised article has to do with the language issue of ?parallel construction.? In paragraph (1), it is telling us to use the larger of (a) or (b). But it speaks of ?larger? in the context of the larger amount of current. The words are, ?. . . sized to carry not less than the larger of. . . .? That means we are to calculate the currents described in the two following sub-articles, and select a wire that can carry that much current. However, paragraph (a) has us actually calculate a current value, and paragraph (b) does not. So there is no way to select the larger of the two values.

I plan to submit a revision for this issue. But as I am not certain I understand the CMP?s intent, I am not yet sure what new wording to recommend. :?
 
charlie b said:
My problem with this revised article has to do with the language issue of ?parallel construction.? In paragraph (1), it is telling us to use the larger of (a) or (b). But it speaks of ?larger? in the context of the larger amount of current. The words are, ?. . . sized to carry not less than the larger of. . . .? That means we are to calculate the currents described in the two following sub-articles, and select a wire that can carry that much current. However, paragraph (a) has us actually calculate a current value, and paragraph (b) does not. So there is no way to select the larger of the two values.

I plan to submit a revision for this issue. But as I am not certain I understand the CMP?s intent, I am not yet sure what new wording to recommend. :?
Click to expand...
My [deleted :rant:] Public Input for 215.2(A)(1) went something like this:

(1) General. Feeder conductor ampacity rating shall be not less than the load current value as calculated in Parts III, IV, and V of Article 220. Minimum feeder conductor size shall be not less than the larger of 215.2(A)(1)(a) or (b).

(a) The minimum Table 310.15(B)(16) size, as selected and coordinated with 110.14(C), having allowable ampacity not less than the noncontinuous load current value plus 125 percent of the continuous load current value.

(b) The minimum conductor size having an adjusted and corrected ampacity not less than the load current value.

Exception No. 1 to (a): If the assembly, including the overcurrent devices protecting the feeder(s), is listed for operation at 100 percent of its rating, the allowable ampacity of the feeder conductors shall be permitted to be sized using the non-factored load current value.

Exception No. 2 to (a): Grounded conductors that are not connected to an overcurrent device shall be permitted to be sized using the non-factored load current value.
Click to expand...
 
As soon as you uses the word "ampacity" in any rule, you have automatically included the adjustment and/or correction factors per the Article 100 definition. If you want the rule to use the values from the "ampacity" tables, you have to use wording that specifically says that.
 
don_resqcapt19 said:
As soon as you uses the word "ampacity" in any rule, you have automatically included the adjustment and/or correction factors per the Article 100 definition. If you want the rule to use the values from the "ampacity" tables, you have to use wording that specifically says that.
Click to expand...
I am of the impression the term allowable ampacity refers to unadjusted and uncorrected table values. I realize it is not defined anywhere, though.
 
Smart $ said:
I am of the impression the term allowable ampacity refers to unadjusted and uncorrected table values. I realize it is not defined anywhere, though.
Click to expand...
I don't know that that term means. I see it as meaning the same thing as ampacity.
 
Maybe the tables should all be labelled "base ampacity" to make clear that the corrections and adjustments are made starting from those values?
 
Status
Not open for further replies.
Top