Ser cable ampacity

[mwm1752]

Does this apply to thermal insulation surrounding the SER cable in dertermining the conductor temperature rating of 75C or 60C. If you have 100' run of ser cable with less than 10% in thermal insulation can the 75C amperage be used. Assume your terminals are rated @ 75C.
310.15 Ampacities for Conductors Rated 0?2000 Volts
(A) General.
(2) Selection of Ampacity. Where more than one ampacity applies for a given circuit length, the lowest value shall be used.
Exception: Where two different ampacities apply to adjacent portions of a circuit, the higher ampacity shall be permitted to be used beyond the point of transition, a distance equal to 3.0 m (10 ft) or 10 percent of the circuit length figured at the higher ampacity, whichever is less.

 

[Dennis Alwon]

Unfortunately that exception does not count. Basically ser is the same as nm in many ways however they give a little more leeway with SER. Even though art 338.10(B)(4) says to exclude 334.80 we see that that section excludes 310.15(A)(2) exception. I believe it was suppose to do the same for SER.

 

[Smart $]

Unfortunately that exception does not count. Basically ser is the same as nm in many ways however they give a little more leeway with SER. Even though art 338.10(B)(4) says to exclude 334.80 we see that that section excludes 310.15(A)(2) exception. I believe it was suppose to do the same for SER.

With all due respect, the text does not support your belief... :happyno:

 

[Dennis Alwon]

With all due respect, the text does not support your belief... :happyno:

I know what the text states that why I said I believe the intent to be..... I have talked with many inspectors and heads of state inspection who all see it as I stated. Again I think that is the intent and if you talk with Southwire- they are the ones who got this SER business going they will tell you you cannot use that exception. Same is true with nm going thru a hole that is caulked-- 3" of caulk and the entire run must be derated-- why would that be different for SER inspite of what the actual wording states.

I knew someone would challenge what I said even though I wrote "I believe".

So anyway I think it is bogus but I am quite certain the official verdict would say you can't use the exception. This is definitely the case in NC- exception cannot be used.

 

[mwm1752]

Unfortunately that exception does not count. Basically ser is the same as nm in many ways however they give a little more leeway with SER. Even though art 338.10(B)(4) says to exclude 334.80 we see that that section excludes 310.15(A)(2) exception. I believe it was suppose to do the same for SER.

Could be the exclusion of 334.80 is based upon 338.10(B)(4) refering to the derate process within thermal insulation. If SER was to exclude section 310.15(A)(2) the code should address it ni 338.10(B)(4). I am looking for code reference to allow or disallow 310.15(A)(2) with SER cable

 

[Dennis Alwon]

Could be the exclusion of 334.80 is based upon 338.10(B)(4) refering to the derate process within thermal insulation. If SER was to exclude section 310.15(A)(2) the code should address it ni 338.10(B)(4). I am looking for code reference to allow or disallow 310.15(A)(2) with SER cable

I don't think you will find an answer. For me it is the logic that nm and ser were derated to 60 C because of the thermal insulation that it would normally be installed in. In the 2011 the code panel decided to allow SER at 75C if it was not in insulation. In reality they could do that for nm but the reality of that would make it almost worthless.

So given that SER is really meant to be 60C and given that NM is 60C for the same reasons I would surmise then that the exception in 310.15(A)(2) should not apply. Trust me we tried to use that here and the state would not allow it since Southwire stated that there is damage to a cable even when there is only 3 in of cable going thru a caulked hole. They stated the damage occurs at the hole where the cable is installed thru.

So you can try and get it passed I can only relate how it was told to me and how it is looked at around here. The logic makes sense to me in spite of the fact that I disagree with how they arrived at it. The testing was done at full ampere rating which generally is not seen on se cable as it is used as feeders which often have 125% or some factors built in.

 

[Smart $]

I know what the text states that why I said I believe the intent to be..... I have talked with many inspectors and heads of state inspection who all see it as I stated. Again I think that is the intent and if you talk with Southwire- they are the ones who got this SER business going they will tell you you cannot use that exception. Same is true with nm going thru a hole that is caulked-- 3" of caulk and the entire run must be derated-- why would that be different for SER inspite of what the actual wording states.

I knew someone would challenge what I said even though I wrote "I believe".

So anyway I think it is bogus but I am quite certain the official verdict would say you can't use the exception. This is definitely the case in NC- exception cannot be used.

Quite difficult to contest others belief, but at least you think it is bogus...

However, even if 334.80 were included, note its stipulation is regarding two or more cables without spacing. Add to that it does not disallow 310.15(A)(2) Exception where installed in thermal insulation. That only applies to two NM cables through the same sealed hole in wood framing.

 

[Smart $]

... If you have 100' run of ser cable with less than 10% in thermal insulation can the 75C amperage be used. Assume your terminals are rated @ 75C.

Just so you know, it is not 10% of the entire run. It is 10% of the adjacent portion(s) at the higher ampacity.

For a 100' run with two differing derated ampacities, the higher ampacity portion must be at least 90.9' and the lower ampacity portion not more than 9.1'.

 

[Dennis Alwon]

Quite difficult to contest others belief, but at least you think it is bogus...

Remember my belief is in what Southwire has publicly claimed thus giving me reason to a, at least , understand what was being asked in this section. Unfortunately the 2014 does not clarify it at all

 

[Smart $]

Remember my belief is in what Southwire has publicly claimed thus giving me reason to a, at least , understand what was being asked in this section. Unfortunately the 2014 does not clarify it at all

So noted.

 

[infinity]

Just so you know, it is not 10% of the entire run. It is 10% of the adjacent portion(s) at the higher ampacity.

For a 100' run with two differing derated ampacities, the higher ampacity portion must be at least 90.9' and the lower ampacity portion not more than 9.1'.

Care to explain your math?

 

[Smart $]

Care to explain your math?

The requirement is 10% (or 10', whichever is less) of the adjacent portion's distance.

If you have a 100' run with 10' at the lower ampacity, the adjacent portion can at most be 90'. 10% of 90' is 9'. 10' exceeds the lesser 10% limitation.

Using the following variables:
d_h = distance at higher ampacity
d_l = distance at lower ampacity

d_t = d_h + d_l
d_l < d_h ? 10%

Substitute second equation into first...

d_t < d_h + d_h ? 10%
d_t < d_h ? 110%

Transposing, we get...

d_h > d_t ? 110%

The relationship of d_l to d_t can also be determined by transposing the second equation...

d_h > d_l ? 10%, or d_h > d_l ? 10

...and substituting into first equation...

d_t > d_l ? 10 + d_l
d_t > d_l ? (10 + 1)
d_t > d_l ? 11

NOTE: Substitute less/greater than or equal character for their "red" counterparts above. I would use the actual characters, but they just get parsed by forum programming to a ?.

 

[GoldDigger]

You can also use ">=" and "<=" in a pinch.

Tapatalk!

 

[Dennis Alwon]

Smart made a good call but I bet most ec's or inspectors would catch that. It clearly states 10% of the circuit length figured at the higher ampacity so I would agree with Smart. I actually never caught that before I assumed 10' for 100' run

 

[infinity]

The circuit is 100', 10' is 10%. What am I missing?

 

[GoldDigger]

The circuit is 100', 10' is 10%. What am I missing?

What you are missing is that the 10% is not 10% of the circuit but 10% of the higher ampacity part of the circuit. The language is clear.

If the total length is at least 110', then you can use your full 10' reduced ampacity section.

 

[Dennis Alwon]

The circuit is 100', 10' is 10%. What am I missing?

It says 10% of the circuit at the higher ampacity not 10%% of the entire circuit

 

[ceb58]

I know what the text states that why I said I believe the intent to be..... I have talked with many inspectors and heads of state inspection who all see it as I stated. Again I think that is the intent and if you talk with Southwire- they are the ones who got this SER business going they will tell you you cannot use that exception. Same is true with nm going thru a hole that is caulked-- 3" of caulk and the entire run must be derated-- why would that be different for SER inspite of what the actual wording states.

I knew someone would challenge what I said even though I wrote "I believe".

So anyway I think it is bogus but I am quite certain the official verdict would say you can't use the exception. This is definitely the case in NC- exception cannot be used.

And I have to back what Dennis has stated. Here, the inspectors will tell you that even if it passes through insulation you must use the 60 deg. table.

 

[augie47]

I'm missing something. I see using the higher ampacity for 10 ft or 10% of the circuit length

 

[infinity]

I'm missing something. I see using the higher ampacity for 10 ft or 10% of the circuit length

Seems pretty clear to me.