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Sub panel questions-New thread as to not hijack existing thread

wyliesdiesels

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the panel is still at the same potential as the earth. having an open neutral doesnt change that

what you are describing is parallel pathways.

once again youre mixing things up....

having 2 parallel ungrounded conductors doesnt change their potential. it just creates 2 pathways for the current to flow....

and then mixing in breakers not tripping because the rod doesnt have impedance makes no sense either

the breaker doesnt trip because the earth will not allow enough current to flow. that has absolutely nothing to do with the rod.

then bringing up the main breaker into the mix just shows you are way off base....
 
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Codyboy

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Ok I can see how it creates parallel paths but how is it a shock hazard?
Top drawing is what I have.
The only difference with top drawing compared to the middle drawing is the top drawing has a main breaker only panel between the meter and the other panel. How does having this panel cause a shock hazard?
Doesn't the neutral just go straight through?

Would it make a difference if the neutral just bypassed through the main panel without being terminated in it? Bottom drawing
The main panel would still be grounded with the ground rod and the ground from the 2nd panel.
20260512_130753.jpg
Or I could just eliminate the main panel altogether.
 

dave*99

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Ok I can see how it creates parallel paths but how is it a shock hazard?
Top drawing is what I have.
The only difference with top drawing compared to the middle drawing is the top drawing has a main breaker only panel between the meter and the other panel. How does having this panel cause a shock hazard?
Doesn't the neutral just go straight through?

Would it make a difference if the neutral just bypassed through the main panel without being terminated in it? Bottom drawing
The main panel would still be grounded with the ground rod and the ground from the 2nd panel.
20260512_130753.jpg
Or I could just eliminate the main panel altogether.
It won’t be clear to you until you consider normal voltage drop on the neutral due to neutral current. Then consider the ground wire is sharing those currents. It only supposed to carry fault current. Not neutral current.

Going further:

Then consider an open neutral between main and sub if the sub is bonded. Now your ground wire carries all the neutral current. Homeowner might not know until the ground wire melts and his washing machine chassis on the sub is at 40 volts.

And then there is neutral to earth voltage to consider. Earthing, grounding and bonding is complicated.

And then there is Earth impedance to learn about. Here is a reference:

 

mm08822

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Work with the top sketch only (as is the origin of this entire discussion.)

With no load connected at the sub panel, there is no current flowing in neutral or ground. So there is no real issue (yet).

Now run a 5a load out of the sub panel. 5a goes out on the hot and 5a returns to the subpanel neutral bar from the load neutral. Now that 5a has 2 paths to travel from the subpanel neutral bar back to the main panel neutral bar - neutral and ground wire.

If that neutral were to open all the current runs along the ground wire. When the grd wire has current flowing and you touch different grounded objects that each connect at different points on the grd wire, you can get shocked.

Same is true if the neutral weren't open just to a lesser degree b/c less vd on the grounded conductor due to lower current flowing on it.

Grd wire is only meant to carry a high magnitude fault current for msecs. Just enough to cause ocp to trip. Your errant jumper completely changes the function of the grd wire. Also makes it a touch potential shock hazard to other items bonded to it.
 

wyliesdiesels

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anything connected to the neutral bar downstream of the main service and tied back to the main service panel will flow that neutral current. if you touch 2 grounded/bonded objects, there is a potential for the current to go thru you in its trip back to the main....

this is why the code changed in 2008 to prohibit bonded neutral in detached buildings. However code NEVER allowed bonded neutral in subs in the same building as the feeding panel for this reason....
 
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Codyboy

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Thank you all for replying and explaining something that I really already knew but tried to make excuses and lie to myself because I didn't want to have to fix it. So I tried to come up with an alternative.
And yes I know that even in linework that grounds and neutrals although are all connected together they work in different ways in that neutrals carry load and grounds don't unless something is wrong.
My apologies to all.

I'm not too concerned with the ******* and not having each wire clipped in. That will have to stay because I'm not ripping out sheetrock.

As far as adding a ground bar and moving grounds to it , removing the bonding screw...
where is the best place to put that bar?
 

sparky 1971

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As far as adding a ground bar and moving grounds to it , removing the bonding screw...
where is the best place to put that bar?
There are factory hols on both sides of the panel a little above midway between top and bottom. Right now they are buried behind existing wires.
 
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Codyboy

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Yes on the factory holes , I was wondering if putting it horizontal below the bus would be easier.
 

mm08822

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Locate it so the wires reach. Sometime 2 are easier - one left/one right.
The feeder ground wire needs to connect to one of them.
Use tapped machine screw holes to anchor bars to enclosure.
 
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