Residential - Commercial Services

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Hello Pierre

Hello Pierre

In my humble opinion, the main differences between a commercial and residential service are...
1. The voltages involved. 208/120 3-phase or 240/120 1-phase
2. The grounding and bonding. A lot of commercial buildings are steel, have fire piping, water piping, gas piping, transformers, etc; Residential has a ufer ground and possibly a water pipe and gas pipe.
3. And last, but not least is the incoming utility and the amount of underground pipe installation done for a commercial service as compared to a residential service.

It really all depends on how much you have worked on res. or com. jobs and how you interpret the terms and of course your local codes can imply some different meaning. Took my best shot>
 
no de-rating on commercial.
(I see a numer of 200 amp commercial services built with 2/0 cu )
 
augie47 said:
no de-rating on commercial.
(I see a numer of 200 amp commercial services built with 2/0 cu )
Click to expand...

I'm at building with 200amps on #2, we re-fused it to 150amps until we could bring up another 200amp feeder with 3/0. No one noticed the problem till we burned 3 feet of wire over the summer using the hvac system. And this was an inspected job.
 
I don't necessesarily see a difference - I see them the same for the most part. (excluding 277/480) But the POCO here does see them slightly different for reasons of their own. Mostly to do with by-pass equipment and demand factors.

800a 120/208 4 wire UG on it's own transformer for a single family home.... Yep... So one could not include size, phase, OH/UG and voltage (excluding 277/480).

Grounding and bonding is the same....

For that matter - aside of the fact that NM is not allowed in commercial as a local code, and conversly multi-family over 4 stories require MC here - I don't see a difference in any other portion of the electrical work at all.... :roll:

So I guess the short answer is the POCO and the city may see them differently - I don't.
 
Other than the reduction in size allowed for residential services, there is no difference. The POCO may have some different requirements as to size & number of raceways feeding a commercial building but that is about all.

Bonding and grounding requirements are the same.

I do think about fault current for larger commercial projects but I do not believe anyone has ever questioned that for a house. Probably should on some of them.
 
First thing on my mind is a higher value of available fault current is present in most commercial applications than in residential ones. That means PPE. Second is voltage and phases. Third is an increase in insurance certifications required by various officials in the food chain of the customer company. Fourth is every facility has some self appointed chief of " Why wasn't I told about this, you can't do that until I approve"....... Parking / elevator waits/ restricted hours/ parking tickets / abundance of pretty secretaries all can slow down, or raise the cost of the service calls on commercial service.
 
Here it would be bypass/test lugs on the meter for commercial.


And of course the larger service condutors.
 
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