Water pipe and Metal Structure of Commercial

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Electriman

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Good morning,

Lets assume that we are designing the electrical for a warehouse, are we required to bond the metalic structure and water pipes to our ground system and if so what should be the bonding cable size?

Thanks,
 
If either the metallic water system or building steel qualify as grounding electrodes, 250.50/52 require that you connect the them as such. In the event they are not electrodes, 250.104 requires they be bonded.
In either event your grounding electrode conductor/bonding jumper needs to be sized by 250.66 based on your service entrance conductors.
 
augie47 said:
If either the metallic water system or building steel qualify as grounding electrodes, 250.50/52 require that you connect the them as such. In the event they are not electrodes, 250.104 requires they be bonded.
In either event your grounding electrode conductor/bonding jumper needs to be sized by 250.66 based on your service entrance conductors.
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Thank you for the response. So in either case, they have to be bonded even I have a seperate ground rod for my ground system.
 
Yes
(Are you grounding a service or separately derived system...different Code references)
 
augie47 said:
Yes
(Are you grounding a service or separately derived system...different Code references)
Click to expand...

The service drop is coming from utility, I am not sure how the system is grounded on the utility side but I have my own ground system inside the facility.
 
Regardless of the utility grounding, your facility would need to follow 250.24 (A) for a grounded system or 2540.24(E) for an ungrounded system. Each requires a grounding electrode system.
250.104 requires the bonding of the piping and structure when they are not electrodes.
Suggested references 250.24,250.50 & 250.104
 
augie47 said:
Regardless of the utility grounding, your facility would need to follow 250.24 (A) for a grounded system or 2540.24(E) for an ungrounded system. Each requires a grounding electrode system.
250.104 requires the bonding of the piping and structure when they are not electrodes.
Suggested references 250.24,250.50 & 250.104
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Understood. Thanks.
 
Just a comment on Art 250. I often see post asking the size of the GEC for a commercial or residential or industrial facility. Art 250 makes no distinction on the type of occupancy. The rules in Art 250 apply universally.
Here is my favorite question (which can't be answered)
What size ground for a 200 ampere commercial service?
 
a 200 amp commercial service would require 3/0 cu conductors therefore table 250.66 requires minimum #4 cu GEC.

al feeder are 4/0 per 310.15 therefore would require #2 GEC
 
Steven M. H. said:
a 200 amp commercial service would require 3/0 cu conductors therefore table 250.66 requires minimum #4 cu GEC.

al feeder are 4/0 per 310.15 therefore would require #2 GEC
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You are assuming the service conductor size, I believe that was what Tom was getting at. The service size is not the determining factor for GEC size.

Many commecial buildings use larger than the minimum size service conductors.
 
Steven M. H. said:
a 200 amp commercial service would require 3/0 cu conductors therefore table 250.66 requires minimum #4 cu GEC.

al feeder are 4/0 per 310.15 therefore would require #2 GEC
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First thing as iwire mentions, actual service conductor size used is what you need to go with, you can usually count on 3/0 copper or 4/0 alum as minimum size of service conductor for non dwellings at 200 amps, but certainly can have larger conductors for voltage drop reasons.

Second I am seeing #4 cu or #2 al as the minimum GEC for both 3/0 copper and 4/0 aluminum service conductors. Maybe some confusion in your reply over whether the GEC was cu or al?
 
Electriman said:
Thank you for the response. So in either case, they have to be bonded even I have a seperate ground rod for my ground system.
Click to expand...
Don't forget that if there is 20 or more feet of 1/2" or larger re-bar in the footing or foundation, you are required to use that as a grounding electrode. If you have that, there is no code reason to install ground rods.
 
Yes IWire my point exactly. GEC size is based on the ungrounded service conductor size, which goes back to section 240.4 -why we ground and bond...
 
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