Wire size from disconnect to panel?

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Papisox

Member
Location
Niagara
Occupation
Sub
Hello, I have 250 aluminum coming from transformer to disconnect inside house. 200a Panel will be 25’ away. What size wire should be used from disconnect to panel?
 

Papisox

Member
Location
Niagara
Occupation
Sub
It’s not a DIY post. My builders electrician was running what I thought to be an undersized wire to panel, and looking for opinions.
 

Papisox

Member
Location
Niagara
Occupation
Sub
It hasn’t been installed yet, he’s supposed to install Monday, that’s why I was hoping to get opinions to speak with him
 

kwired

Electron manager
Location
NE Nebraska
It will have to be answered by someone familiar with CEC.
That is absolutely true for OP.

Per NEC there are conditions it possibly could appear to be undersized but still be code compliant, but many details can be a factor, including overcurrent protection setting(s), overcurrent protection location(s) conductor installation/routing details (what is considered inside vs outside), and of course basic conductor ampacity rules in general.

If what is in question is considerably smaller than the 250 aluminum supply but has 200 amps or protection chances are his thinking it is undersized may be valid. If it is only slightly smaller, there could be reasons it is still acceptable. If it is copper instead of aluminum it could possibly be smaller than OP may think is allowed and still be legal.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I believe the CEC is similar to NEC in wire size. IMO, it would be 4/0 aluminum at the minimum. It may also require 250 kcm.

What size is the electrician running? Isn't the job getting inspected?
 

kwired

Electron manager
Location
NE Nebraska
I believe the CEC is similar to NEC in wire size. IMO, it would be 4/0 aluminum at the minimum. It may also require 250 kcm.

What size is the electrician running? Isn't the job getting inspected?
He didn't give enough details to confirm anything though. That would cover what is likely majority of time with what little info we have.

If they happen to change over to copper inside it could be even smaller conductors.
 

Papisox

Member
Location
Niagara
Occupation
Sub
He is saying 2/0 copper to the panel. Yes it is a new build being inspected, and we have permit. I’m sure the inspector will tell him if undersized, I was just asking a question.
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
See table 2 of the CEC,
especially note ††
CEC said:
For 3-wire 120/240 V and 120/208 V service conductors for single dwellings, or for feeder conductors supplying
single dwelling units of row housing of apartment and similar buildings, and sized in accordance with
Rules 8-200(1), 8-200(2), and 8-202(1), the allowable ampacity for sizes No. 6 and No. 2/0 AWG shall be 60 A
and 200 A, respectively. In this case, the 5% adjustment of Rule 8-106(1) cannot be applied.
my version is pretty old now but I don't think its changed.
 
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