# GFI Neutral and distance to the main ground

• posted on December 5, 2005, 3:52 pm
The Neutral and Ground are together at one place in the circuit breaker box.
If, for example, you had a neutral short to ground within 2 or 3 feet of the breaker box, would a GFI be able to detect the short?
In other words, within a few feet, is there any practical difference betweern Neutral and Ground?
Is there a minimum distance where it begins to matter?
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on December 5, 2005, 4:08 pm

A GFI will detect any "neutral short" downstream of the GFI. So if you had a GFI breaker in the breaker box, then a "neutral short" 2 feet away on that circuit would be detected. The neutral wire in that circuit goes directly to the GFI, not to the neutral bar.
Cheers, Wayne
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on December 5, 2005, 6:26 pm
Wayne Whitney wrote:

Would you please explain why that is Wayne?
While I certainly agree that you should not intentionally connect neutral to ground anywhere but at the service panel.
To keep it simple, assume we're talking about a GFI breaker servicing just one receptical:
If by "neutral short" you mean making a connection between the neutral lead screw on the GFI and the ground lead it's location, with no current flowing in the hot lead from that GFI and no currents imposed on the neutral or ground through paths to/from other things.
Under those conditions the neutral current and the hot current from the GFI are both zero, and zero equals zero. So, there should be no current imbalance for the GFI to detect and trip from.
If you put a load on that receptical, then I'd expect the GFI to trip because the shared part of the return current on the ground lead would not be seen by the GFI, so an inbalance would be sensed.
Am I missing something here?
Jeff
--
Jeffry Wisnia

(W1BSV + Brass Rat \'57 EE)
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on December 5, 2005, 7:20 pm
Yes read the URL I posted above just above the 3rd illustration under: Neutral to Ground fault detection. I knew GFCIs could do this but wasn't clear how. Now I also know. Rlchard
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on December 5, 2005, 8:19 pm

You learn something everyday. I originally just meant that a Neutral to Ground fault would be detected when you apply a load, but as stated some GFCIs detect them as soon as power is applied.
Cheers, Wayne
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on December 5, 2005, 9:15 pm
snipped-for-privacy@lycos.com wrote:

This message is being keyboarded in by a monkey's uncle.
Wot won't they think of next?
Thanks for the lesson, I needed it.
Jeff
--
Jeffry Wisnia

(W1BSV + Brass Rat \'57 EE)
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on December 5, 2005, 5:11 pm

Would depend on the location of the gfci.
It matters always. Any intentional connecting of the neutral and ground after the service is wrong.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on December 5, 2005, 5:38 pm
Most GFCIs will test for the grounded neutral condition. Read this by Sam Goldwasser:
http://www.codecheck.com/gfci_principal.htm
I've seen that grounded neutral problem a lot. The last time was in a garage where someone had put in a new outlet they wired the incoming white wire to the box. Unfortunately they also ran the feed to the garage in BX that ran on the floor under the entry door. Salt corroded this BX to the point that the armor shield and the neutral opened up. When their 16 year old son flipped on the light during a rainstorm he got a hell of a shock.
Richard