When supplying a grounding electrode for separately derived AC systems 250.30(A)(4)(1)(2002 NEC) states you can use an effectively grounded structural metal member of the structure. Is there any definition or guidlines required for "effectively grounded" (ie solid #3 bonding all building steel)?
Effectively grounded Building Steel
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- Bremerton, Washington
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- Master Electrician
Re: Effectively grounded Building Steel
One way it has been explained is the building steel foundation bolts are cadwelded to the reiforcing steel in the building foundation.
Erico has a lot of information on this subject.
However there is not a clear cut definition similar to the 25 ohms resistance for ground rods.
One way it has been explained is the building steel foundation bolts are cadwelded to the reiforcing steel in the building foundation.
Erico has a lot of information on this subject.
However there is not a clear cut definition similar to the 25 ohms resistance for ground rods.
- Location
- Massachusetts
Re: Effectively grounded Building Steel
In a typical steel frame building the steel will be bonded to the ground bus at the main service, this with the fact that the beams are bolted to anchor bolts in the cement footing should make the steel "effectively grounded".
But as already stated it can go beyond that, I just started a new job Cadwelding #2 bare to rebar's in the footings, foundation walls, when the floor goes in we will pick up the rebar in that too, also about 50% of the steel columns will have #2 cadwelded to them at the base
All these #2 bare Cadweld to a 4/0 Bare "ground ring" around the building and to about a dozen 10' x 3/4" ground rods, with 2, 4/0 T-Taps off of the ring back to the service gear.
[ March 21, 2003, 05:54 PM: Message edited by: iwire ]
In a typical steel frame building the steel will be bonded to the ground bus at the main service, this with the fact that the beams are bolted to anchor bolts in the cement footing should make the steel "effectively grounded".
But as already stated it can go beyond that, I just started a new job Cadwelding #2 bare to rebar's in the footings, foundation walls, when the floor goes in we will pick up the rebar in that too, also about 50% of the steel columns will have #2 cadwelded to them at the base
All these #2 bare Cadweld to a 4/0 Bare "ground ring" around the building and to about a dozen 10' x 3/4" ground rods, with 2, 4/0 T-Taps off of the ring back to the service gear.
[ March 21, 2003, 05:54 PM: Message edited by: iwire ]
- Location
- Massachusetts
Re: Effectively grounded Building Steel
I would like to add be carefull in older buildings.
We work in some old mill buildings and many times the steel that has been added over the years is not effectively grounded.
I would like to add be carefull in older buildings.
We work in some old mill buildings and many times the steel that has been added over the years is not effectively grounded.
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