Overhead Service wire sized from 90 c or 75 c table ?

[FWD]

I have one 200 amp commercial meter panel and one 150 amp residential meter panel connected under a gutter with the service riser extending out of the top of the gutter . Service conductors will split to their respective meter panels via Polaris connectors rated @ 90c . Would it be legal to size the service entrance wires using the 90 c column , or do I need to use the 75 c column for the wires extending from the weather head into the gutter ? Appreciate the help , Thank You !

 

[Dennis Alwon]

Since the equipment is usually rated 75C you need to use the 75C rating. You can use the 90C for derating but the final ampacity cannot be more than the 75C rating

 

[Strathead]

I have one 200 amp commercial meter panel and one 150 amp residential meter panel connected under a gutter with the service riser extending out of the top of the gutter . Service conductors will split to their respective meter panels via Polaris connectors rated @ 90c . Would it be legal to size the service entrance wires using the 90 c column , or do I need to use the 75 c column for the wires extending from the weather head into the gutter ? Appreciate the help , Thank You !

What you didn't state, was what the wires terminate to in the gutter. Or at least that is what I interpreted. The Polaris lugs you referred to are at the weatherhead. That is why Dennis said no. If the conductors terminate in 90 degree terminations in the gutter as well then they can be sized per the 90 degree table.

 

[Dennis Alwon]

What you didn't state, was what the wires terminate to in the gutter. Or at least that is what I interpreted. The Polaris lugs you referred to are at the weatherhead. That is why Dennis said no. If the conductors terminate in 90 degree terminations in the gutter as well then they can be sized per the 90 degree table.

That is correct. The wires to the polaris lugs can be 90C rated but the taps need to be based on 75C. Sorry I misunderstood what you were asking

 

[FWD]

Overhead service

Overhead service

To follow up , yes the service conductors from the weather head can be sized from 90 c column if they terminate in 90 c rated Polaris connectors in the gutter , then split to their respective meter panels with 75 c rated conductor . Correct ? Thanks again , appreciated !

 

[Strathead]

To follow up , yes the service conductors from the weather head can be sized from 90 c column if they terminate in 90 c rated Polaris connectors in the gutter , then split to their respective meter panels with 75 c rated conductor . Correct ? Thanks again , appreciated !

correct

 

[FWD]

10/4 Thanks again !

 

[texie]

To follow up , yes the service conductors from the weather head can be sized from 90 c column if they terminate in 90 c rated Polaris connectors in the gutter , then split to their respective meter panels with 75 c rated conductor . Correct ? Thanks again , appreciated !

A gold star for efficient use of the rules. Now just try to explain this to the garden variety ICC wizard inspector in many jurisdictions.

 

[Gary11734]

I wonder if this is considered a wet location? If yes, only 75-degree conductor rating.

 

[augie47]

I wonder if this is considered a wet location? If yes, only 75-degree conductor rating.

I don't see a conductor type mentioned but some are 90° wet or dry.

 

[Gary11734]

I don't see a conductor type mentioned but some are 90° wet or dry.

The condition is putting the wire at 75 degrees. They don't want the wire to boil water. So, you can only load the wire to 75 degrees before you are against the code.

 

[infinity]

The condition is putting the wire at 75 degrees. They don't want the wire to boil water. So, you can only load the wire to 75 degrees before you are against the code.

There are wet location conductors that are rated at 90° C. XHHW-2 and THWN-2 just to name a few.

 

[augie47]

The condition is putting the wire at 75 degrees. They don't want the wire to boil water. So, you can only load the wire to 75 degrees before you are against the code.

Huh ?

It's a bit rare but he has identified one of the conditions where he can install and use the wire at it's 90° ampacity and, with the right conductor, be totally Code compliant wet or dry.

 

[Gary11734]

There are wet location conductors that are rated at 90° C. XHHW-2 and THWN-2 just to name a few.

They may be rated for 90 degrees. Doesn't mean you can load them to 90 degrees in some applications. I think the -2 puts them back to 75 degrees in this instance. I'm going to check.

I know the -2 gave me a headache on a previous project. I can't remember what it was...

 

[infinity]

They may be rated for 90 degrees. Doesn't mean you can load them to 90 degrees in some applications. I think the -2 puts them back to 75 degrees in this instance. I'm going to check.

I know the -2 gave me a headache on a previous project. I can't remember what it was...

This is a wet location so the-2 conductor can be sized according to it's 90° C ampacity.

 

[electrofelon]

I wonder if this is considered a wet location? If yes, only 75-degree conductor rating.

I think pretty much all conductors are thwn-2/xhhw-2 now so 90 degrees wet or dry. Most of us still say "THHN" but its just an academic distinction to say that is dry only or 90 only if dry.

 

[FWD]

Thinking about THWN-2 sunlight and wet location at 90 c .

 

[FWD]

also XHHW-2 sunlight and wet location at 90c . depends on price .....

 

[FWD]

Exposed wire extending from weather head must be sunlight resistant also rated for wet location at 90 c in this case . Please correct me if i'm wrong .

 

[augie47]

Exposed wire extending from weather head must be sunlight resistant also rated for wet location at 90 c in this case . Please correct me if i'm wrong .

sunlight & wet location, yes. The 90° is not a general requirement as far as I know but would be in your particular situation if you want to use the 90° ampacity.
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