Review my results and code sections please!

[augie47]

Ok I agree with you Augie, but as you stated 215.2 is the minimum which meets code coorect? Now before we get to far I'm planning on running same size neutral, but how would an inspector fail an installation per 215.2? I don't believe he would do a calculation if he did it would be the first time I witnessed it.

come on down! I have done them, but I like the old adage "don't make their problem your problem"... If you want to reduce the neutral show me the calculations. I've done dozens, looked at hundreds and don't recall any residential requiring a 200 amp service where the calculated neutral was as small as 215.2 would allow.

 

[One-eyed Jack]

Ok I agree with you Augie, but as you stated 215.2 is the minimum which meets code coorect? Now before we get to far I'm planning on running same size neutral, but how would an inspector fail an installation per 215.2? I don't believe he would do a calculation if he did it would be the first time I witnessed it.

The inspector would not do the calculation ordinarily. He could ask you for your calculations to review if he had doubts about your size conductors. It is just not good practice to size the grounded conductor based on 250.122. This is a bare "minimum" size.

 

[brichter]

Seems to be a mental block here. If the calculated load for the grounded conductor is, say 20 amps, the conductor would still need to be the minimum # 6 or whatever is listed.

A calculated load of say 100 amps for the grounded would require a conductor rated for at least 100 amps is required.

Does this sound reasonable?

 

[augie47]

yes... with the possible notation that the 1st statement is for feeders.
I assume you could have a #12 neutral on a 40 amp branch circuit under specific conditions.

 

[brichter]

Seems to be a mental block here. If the calculated load for the grounded conductor is, say 20 amps, the conductor would still need to be the minimum # 6 or whatever is listed.

A calculated load of say 100 amps for the grounded would require a conductor rated for at least 100 amps is required.

Does this sound reasonable?

Should say:

A calculated load of say 100 amps for the grounded conductor would require a conductor rated for at least 100 amps.

 

[geovan]

Ok did some digging here and I'm not sure if I understand you. 215.2(A)(1) points me to 250.122 to size my grounded conductor. This installation would be considered a feeder. :-?

Bingo. 250.66 is EGC

 

[fishin' electrician]

Would not work here.
First, the fact that the garage is power off the service would mean the feeders to the house were not carrying the entire load and 310.15(B)(6) could not be used.

Wouldn't that only be true for an attached garage? There is no mention of which in the OP. I would think if the house and garage are detached 310.15(B)(6) would apply.

 

[augie47]

Possible... I think you might get different answers from different AHJs...to me the new wording in 2008 "For application of this section, the main power feeder shall be the feeder between the main disconnect and the panelboard that supplies, either by branch circuits or by feeders, or both, all loads that are part or associated with the dwelling unit." would include a detached garage as associated with

 

[dana1028]

Ok I agree with you Augie, but as you stated 215.2 is the minimum which meets code coorect? Now before we get to far I'm planning on running same size neutral, but how would an inspector fail an installation per 215.2? I don't believe he would do a calculation if he did it would be the first time I witnessed it.

As others have already posted - as an inspector I would not perform any calc's...I'd require the contractor to show me his calculations.

 

[dana1028]

Feeder size

Feeder size

Unless this is a very large house with lots of electrical appliances it's unlikely it would need a full 200A. Do the calcs and your conductors [you are trying to use from Table 310.15(B)(6)] are most likely plenty large enough.

 

[fishin' electrician]

Possible... I think you might get different answers from different AHJs...to me the new wording in 2008 "For application of this section, the main power feeder shall be the feeder between the main disconnect and the panelboard that supplies, either by branch circuits or by feeders, or both, all loads that are part or associated with the dwelling unit." would include a detached garage as associated with

Hmm, interesting. I'm still on the '05 but I don't see how, even with that wording, that the garage loads are part of the dwelling feeder when the service hits the garage first.

 

[augie47]

again..point of view... mine is that the service is feeding the residence, part of which is the garage. The feeder is supplying the living area but that does not constitute the entire load associated with the dwelling.
Likewise, although I don't necessarily agree, if the heat and air unit is fed off an outside meter/combo, the feeder to the interior panel is not a "whole house" feeder.
If the garage was attached and had a sub panel as did the living area, we would not consider either of those feeders to be "whole house". Detaching the garage doesn't change the load.

 

[A/A Fuel GTX]

Would not work here.
First, the fact that the garage is power off the service would mean the feeders to the house were not carrying the entire load and 310.15(B)(6) could not be used.

This is why 310.15 (B) (6) is sometimes hard to grasp. What if we had a service consisting of a meter socket and an exterior feed through load center with a main breaker and eight spaces. We then put in a 2P 100A breaker which powers a feeder to an interior panel in the dwelling. Ok...everything is fine with using the values in the forementioned table, correct? Now someone comes along and puts a breaker in one of the remaining six spaces in the feed through load center for another branch circuit. Is the size of the feeder now in violation because it no longer carries the entire load of the dwelling:-?

 

[suemarkp]

Technically yes, which is why 310.15(B)(6) is still worded stupid.

Even worse is the 200A feed through example (200A feeder from garage to house). If 200A is enough for house + garage and you can use 310.15(B)(6) for that, why can't you use the same size wire to the house where you know the load can not be any greater than what serves the house + garage? Then lets try and use SER for that feeder and really fan the flames.

They really need to decide what part of the dwelling loads are diverse and constitute the core requirements to use 310.15(B)(6). Then, allow panelboards that meet that diversity requirement to use 310.15(B)(6).

I'd suggest that a panelboard with 2 or more "120V general purpose" branch circuits with a calculated load and 2 or more "small appliance or laundry" branch circuits with a calculated load and 1 or more 120V circuit with no calculated load (e.g. bathroom, garage, exterior receptacles) be considered a diverse panel. I'd really like those numbers to be 3 + 3 + 2, but smaller houses may be eliminated in that case.

 

[Strahan]

Sorry guys work night shift and also do part time work during the day. Wish I could have gotten back sooner. Panel is a feed through type so I'm good there. I just don't understand why 310.15(B)(6) doesn't apply. I would treat this strictly as a feeder installation and don't see it any other way.

 

[augie47]

It is a feeder, it's just not, IMO, a "whole house feeder" for reasons stated earlier.

 

[Strahan]

It is a feeder, it's just not, IMO, a "whole house feeder" for reasons stated earlier.

Yea thats the problem! I have read the earlier posts and plan on re-reading them, but this "feeder" in my opinion is a whole house feeder. The house is a seperate structure. Whats the difference when we run the service to the house and then run a feeder to the detached garage and install a panel. I don't see the difference. So if it is a feeder then 3/0 ungrounded conductors (including the neutral) and a 6AWG EGC. I don't mean to keep beating a dead horse, but would you accept this installation?

 

[augie47]

I'm not the one that needs to , but, yes.
More often than not, here the neutral would probably be a 2/0 or 1/0 and still be acceptable. (assuming you have some 240v loads)

 

[Strahan]

I'm not the one that needs to , but, yes.
More often than not, here the neutral would probably be a 2/0 or 1/0 and still be acceptable. (assuming you have some 240v loads)

Thanks Augie! Don't mean to be a pain I'm just trying to grasp all of this.

 

[Article 90.1]

My interpretation is that if your service is installed on the detached garage, then feeds the "dwelling unit," that Table 310.15(B)(6) is not applicable. If, however your service were to originate at the dwelling unit, then feed the garage, then we could worry about applying T310.15(B)(6), or not. Inspectors, what say thee?