[TheForge] Grounding Points in Concrete Floors

[Jerry Frost]

Bill:

I uploaded a pic of the first concrete going into the footings/slab of my 
new shop. (For some reason photoaccess wants a minimum file size so most of 
my pics were unacceptible) The pic shows the infloor sockets and rebar 
welded to them for grounding.

I don't know how much induction heating to expect but at the amperages I 
typically use 100- it's insignificant. Still, every socket in my floor has a 
minimum of two pieces of #4 rebar welded to it. All the rebar is welded in a 
4' x 4' grid. Rebar is sized in 1/8" increments so 1/2" is #4, 5/8 is #5, 
etc.

Another thought for providing a grounded grid is to have steel laid in the 
concrete flush with the surface. Common in heavy duty shops is RR rail, 
sometimes flange up, sometimes rail up. If it's welded into the rebar 
reinforcing it makes a grounded grid. The advantage of this is you can weld 
things to it, say a deadman/anchor for straightening or bending beams, 
frames, etc.

You don't need RR rail though, angle iron, "I" beam, etc. welded into the 
rebar grid with the flange flush with the floor works fine. I wouldn't use 
less then 1/4" though.

Frosty
------------------------
If it ain't forged
it ain't real.
Wrought iron is.
The FrostWorks

Meadow Lakes, AK.


----- Original Message ----- 
From: "Woolley" <wjec at verizon.net>
To: <theforge at mailman.qth.net>
Sent: Thursday, August 25, 2005 6:22 AM
Subject: [TheForge] Grounding Points in Concrete Floors


Greetings,

I've seen some of the posts on new concrete floors being poured with 
grounding points for welding etc.at various places.  I'm about to do the 
same thing and was wondering what everyone used (must have missed this) as 
their ground path underground.  I was going to use 1/2 rebar (I know rebar 
is a # size, can't remember it) for my path, and basically bring it above 
the concrete at various spots along the perimeter walls.  Is this 
sufficient?  Will the heat conducted thru the path adversely effect the 
concrete? Thanks.

Regards,
Bill Woolley
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