4/0 Al SER Cable vs 200a rating

[steveve1]

Hi Guys, It's been a while. We have installed 4/0 Al SER cable to provide 200 amp service to interior mounted panels. As the connection lugs of the connected equipment are rated at 75 deg C, the ampacity rating of the conductors is reduced to 180 amps per the 75 deg column, but 240.4 allows OCP to be 200 amp as the next standard rating. As 2' of the conductors terminate in an exterior cabinet exposed to our Arizona temps, the engineer has called for an ambient correction factor of .82, thus allowing an ampacity of the installed cable at 148 amps. What say you? Thanks always.

 

[Buck Parrish]

I say he must not have heard of AC.


As long as you are not bundled or on a roof. Your code compliant.

 

[Dennis Alwon]

Hi Guys, It's been a while. We have installed 4/0 Al SER cable to provide 200 amp service to interior mounted panels. As the connection lugs of the connected equipment are rated at 75 deg C, the ampacity rating of the conductors is reduced to 180 amps per the 75 deg column, but 240.4 allows OCP to be 200 amp as the next standard rating. As 2' of the conductors terminate in an exterior cabinet exposed to our Arizona temps, the engineer has called for an ambient correction factor of .82, thus allowing an ampacity of the installed cable at 148 amps. What say you? Thanks always.

Two things.
First, Ser cable may not be used at 75C any more. Read art. 338.10(B)(4)(a) and then art. 334.80. SE cable used for interior wiring must be used at 60C.

Second, art. 310.15(A)(2) comes into play here. I would think the engineer is off on that one if only 2 feet is exposed to the hot temp.

Add: The ser change is in the 2008 code

 

[Cow]

Try 310.15(A)2 Exc.

 

[iwire]

First, Ser cable may not be used at 75C any more.

A bit misleading, SE can still be used at 75C outside and inside when used as service entrance conductors.

We don't have enough info to know if the interior SE is a feeder or service conductor.

Second, art. 310.15(A)(2) comes into play here. I would think the engineer is off on that one if only 2 feet is exposed to the hot temp.

I do not understand this, how can the engineer be 'off base' if the engineer designed the jib they can ask for whatever they want and if it is in the plans or specs that is what has to go in.

I have run 2400 amps of copper for a 1600 amp feeder that was only about 200' long because that was what the engineer specified.

 

[iwire]

We have installed 4/0 Al SER cable to provide 200 amp service to interior mounted panels.

Is the over current protection inside or outside?

As 2' of the conductors terminate in an exterior cabinet exposed to our Arizona temps, the engineer has called for an ambient correction factor of .82, thus allowing an ampacity of the installed cable at 148 amps. What say you?

I say who is the engineer in relation to the job?

Are they in charge of the electrical design or not?

 

[infinity]

More info is needed to properly answer the question (see Bob's post). I would agree that according to the NEC, the 2' of cable would not require any derating due to 310.15(A)(2)Ex as Cow and Dennis pointed out.

 

[Dennis Alwon]

A bit misleading, SE can still be used at 75C outside and inside when used as service entrance conductors.

It is not misleading if you read the second sentence of my post about interior wiring.

We don't have enough info to know if the interior SE is a feeder or service conductor.

You may be correct if it it 3 phase but I assumed single phase. But we all know about what happens when we assume. :smile:

 

[iwire]

It is not misleading if you read the second sentence of my post about interior wiring.

I did read your entire post, I still feel your post could confuse some. It is like the wording of 312.8 at first glance it says one thing but read on and it reverses itself. :smile:

You may be correct if it it 3 phase but I assumed single phase.

I have no idea why single or three phase would make a difference.

If the service disconnect is outside, then the section of SE cable inside is subject to the 60 C limitation, if the service disconnect is inside the SE cable can be used at 75 C all the way to the panel even if it's located inside.

 

[Dennis Alwon]

I did read your entire post, I still feel your post could confuse some. It is like the wording of 312.8 at first glance it says one thing but read on and it reverses itself. :smile:




I have no idea why single or three phase would make a difference.

If the service disconnect is outside, then the section of SE cable inside is subject to the 60 C limitation, if the service disconnect is inside the SE cable can be used at 75 C all the way to the panel even if it's located inside.

Because the se cable is SER as stated by the OP. That would be a feeder for single phase

 

[iwire]

Because the se cable is SER as stated by the OP. That would be a feeder for single phase

OK I see where your coming from. :smile:

 

[suemarkp]

What are the conductor types inside the SE? Are they 90C rated so you can do thermal derating from the 90C ampacity instead of 75C (just like NM is limited to 60C ampacity but deratings are done from 90C)?

Also, is this for an individual dwelling and does it have a 200A service? If so, you may not be required to size any feeder larger than the service entrance conductors per 215.2(A)(3).

 

[chris kennedy]

What are the conductor types inside the SE? Are they 90C rated so you can do thermal derating from the 90C ampacity instead of 75C (just like NM is limited to 60C ampacity but deratings are done from 90C)?

They are 90?C conductors.

View attachment 2404

 

[steveve1]

Gentlemen, Thank you for your posts. 310.15(2)Exp. gets it done code wise. Now to convince the engineer. Thanks again!

 

[hmspe]

Gentlemen, Thank you for your posts. 310.15(2)Exp. gets it done code wise. Now to convince the engineer. Thanks again!

Where exactly does the SER run? Through an attic? In conditioned space? Underground? In might make a difference. Attics will not be at 86 degF. As an engineer in Arizona I agree with the .82 multiplier unless it's clear that the cable is on conditioned space for most of the run.

Martin

 

[George Newman Jr.]

Hi Guys, It's been a while. We have installed 4/0 Al SER cable to provide 200 amp service to interior mounted panels. As the connection lugs of the connected equipment are rated at 75 deg C, the ampacity rating of the conductors is reduced to 180 amps per the 75 deg column, but 240.4 allows OCP to be 200 amp as the next standard rating. As 2' of the conductors terminate in an exterior cabinet exposed to our Arizona temps, the engineer has called for an ambient correction factor of .82, thus allowing an ampacity of the installed cable at 148 amps. What say you? Thanks always.

Correction factor: 4/0 Ser Xhhw 90 degree column wire rated @ 205 amps before correction X CF of .82 = 168.1 next size up 175 amp OCP Caution be sure feeder Calc. does not exceed 168 Amps!!!