ECN Forum Forums Code Related Discussion NEC & other Code issues grounding electrode system bus

Iwire...I see those pictures do point out this change very clearly....although there are no sizes established in the pictures.

Would the jumper from the bus to the grounded service conductor in the service equipment have to be the same size as the GEC, which is based on the size of the largest ungrounded service-entrance conductor?

jsherrard's description in his post has a 1/0 connecting to each panel which is smaller than the GEC which is 2/0 from the bus to the electrodes.

shortcircuit

That is a good observation one I also noticed but he is correct.

He has a 800 amp service consisting of two 400 amp panels.

The GEC tap from each panel to the grounding bus is based on only the service conductors feeding the panel it comes from.

Now the bonding jumper from the grounding bus to the water main has to be sized on the total service conductor size.

This is covered by 250.64(D)

Considering the conductors from the panel to the grounding bus are called GEC Taps and the conductors from the grounding bus to the electrodes are called bonding jumpers, the only GEC in his installation may be the grounding bus itself.

Bob



[This message has been edited by iwire (edited 02-15-2005).]

Ok... I read 250.64(D)...which allows this arrangement.

But...would these taps to the 400 amp panels be of sufficent size to handle the ground-fault current that may be available from utility source?

Wouldn't the size of the main ungrounded service-entrance conductors(or equivalent size) in jsherrad's (which is a 1000 circular mills) and the neutral be capable of ground-fault current greater those taps can handle?

I thought that table 250.66 bases the size of the GEC according to the largest ungrounded service-entrance conductor for this reason

shortcircuit

I am in a hurry and I will get back to this.

Short answer is the GEC for one particular panel only has to handle what the service conductors feeding that particular panel can supply.

Bob

In electrical control panels, busbar (Bus bar) is a aluminium/copper strip or bar. This busbar is installed inside the panel with the help of insulators and colour coded via coloured shrinkable sleeves. Busbar can be installed in Panels, Busducts, busbar chambers for locally transmission and distribution of power.