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Old 07-24-2010, 08:26 PM   #16
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strange electric problem in new house, hot ground!


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No, it would be connecting the ground to the neutral which is what it takes to make a dead short to the grounding system in the house trip a breaker.
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Ok, I am understanding better. I don't know exactly how my electrician connected everything up, I'll have to have him over here to explain everything.

One confusion I still have, if that 4th wire just connects the ground to the neutral at the pole why is that different than using the bonding screw at the neutral in my 200 amp panel. Even though I understand it is technically a sub panel, how is it really any different than a main panel that would have the neutral bonded to the panel and essentially to the ground?

OH btw-I connected the neutral properly to my dryer in the panel and it worked fine. Just to be safe I had everything else turned off and even unplugged everything I could find to unplug, for testing purposes. It seems to work fine but I realize I still have the grounding problem & I'll have my electrician install the 4th grounding wire.

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Old 07-24-2010, 08:40 PM   #17
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strange electric problem in new house, hot ground!


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One confusion I still have, if that 4th wire just connects the ground to the neutral at the pole why is that different than using the bonding screw at the neutral in my 200 amp panel. Even though I understand it is technically a sub panel, how is it really any different than a main panel that would have the neutral bonded to the panel and essentially to the ground?
First, you said it was not bonded so I presume the screw is not screwed down.

If that screw was screwed down and the neut and ground bonded, it would connect the neut and grounding systems so any current imposed on the grounding system could return to it's ssource (the POCO transformer) which is what it takes to make a breaker trip on a short circuit fault.


and why not just run the screw down? because the code directs what we have to do in such an installation.

at one point in time, as long as there were certain other rules followed, that would have been acceptable. Now the code has changed the allowance of such an installation.





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OH btw-I connected the neutral properly to my dryer in the panel and it worked fine. Just to be safe I had everything else turned off and even unplugged everything I could find to unplug, for testing purposes. It seems to work fine but I realize I still have the grounding problem & I'll have my electrician install the 4th grounding wire.
it should work fine but you have an unsafe condition throughout your house. Your grounding system isn't going to save your butt by allowing current to flow so a breaker will trip on a high current short.
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Old 07-24-2010, 08:47 PM   #18
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Ok, thanks. And you are right, the bonding screw is not installed. I understand it is for code reasons but I just wanted to understand why it was any different. In my previous house I only had a disconnect in the panel so I assume it was ok to have the neutral bonded, hence a 3 wire service wire would be fine, right? I just am not sure I understand what added safety you get from not bonding the neutral in a subpanel. And apparently the only thing that makes mine a subpanel is the fact that the power company installed a breaker at the pole. The previous power company at my other house didn't do this.

Anyway, thanks for all the replies. I'm getting my electrician out to go over everything. btw-we do get breaker trips for various reasons, overloading and some others I can't remember why.. But that probably doens't mean everything is fine I know..
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Old 07-24-2010, 09:21 PM   #19
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I understand it is for code reasons but I just wanted to understand why it was any different. In my previous house I only had a disconnect in the panel so I assume it was ok to have the neutral bonded, hence a 3 wire service wire would be fine, right?
yes

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I just am not sure I understand what added safety you get from not bonding the neutral in a subpanel.
there are different situations that allow different complications. In your situation, if there are any other metallic conductors (phone line, cable tv, whatever) since they are also grounded, if you combine the neutral and the ground from one structure to another, you have the possibility of those other conductors also carrying current. Not god for safety.

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And apparently the only thing that makes mine a subpanel is the fact that the power company installed a breaker at the pole.
yes

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The previous power company at my other house didn't do this.
your install is a bit odd compared to any around my area. Rarely is a disco installled away from the house.

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btw-we do get breaker trips for various reasons, overloading and some others I can't remember why..
the lack of the ground will not affect overload trips (30 amps draw on a 20 amp circuit and such) since those are based purely on heat. A dead short can allow a lot of amps and without that ground wire in place, it cannot flow to the source (the POCO transformer) and it will not trip the breaker. Two different means of tripping a breaker.

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But that probably doens't mean everything is fine I know..[
right. I suspect your trips are due to overloads, not short circuit faults.
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Old 07-24-2010, 10:43 PM   #20
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so having the neutral bonded at the panel if there is no disconnect before the panel would not have the same issues w/ cable, phone lines, etc?

Ok, so my next question is this: If I ask the power company to remove the breaker from the pole, would I be ok with the 3 wires if I had them bond the neutral to the panel? Assuming I find out that I don't have the 4th grounding wire already.

The installer never asked if I wanted a breaker, just asked what size I wanted. It is a small utility and mostly rural, I assume that's why they install a breaker for safety reasons because most people would do a lot of their own electrical work at the panel and they don't want to be removing the meter all the time.

Thanks for all the feedback. Although I still am very unclear how my "subpanel" is really any different than a main panel (other than the extra breaker at the pole) and therefore not allowed to bond the neutral by code.. I don't see a physical difference between that or running a 4th wire all the way back to the neutral at the pole, other than there being a larger path back w/ the 2 wires.
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Old 07-24-2010, 11:02 PM   #21
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strange electric problem in new house, hot ground!


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Ok, thanks. And you are right, the bonding screw is not installed. I understand it is for code reasons but I just wanted to understand why it was any different. In my previous house I only had a disconnect in the panel so I assume it was ok to have the neutral bonded, hence a 3 wire service wire would be fine, right? I just am not sure I understand what added safety you get from not bonding the neutral in a subpanel. And apparently the only thing that makes mine a subpanel is the fact that the power company installed a breaker at the pole. The previous power company at my other house didn't do this.

Anyway, thanks for all the replies. I'm getting my electrician out to go over everything. btw-we do get breaker trips for various reasons, overloading and some others I can't remember why.. But that probably doens't mean everything is fine I know..
You get breakers tripping on overloads because the neutrals (grounded legs) are connected to the neutral bar and therefore a low impedance back to the transformer. These are not ground faults.

It may be worth your while to talk to the POCO and county to see if they will allow a 3 wire feed with bonded panel at the house. BTW you should also have some means of disconnect located at the house to be code compliant. Anyway in your situation the county should be able to tell you what code cycle they enforce. In 2008 they prohibited any 3 wire feeders like you have installed. It used to be quite common in rural areas before 2008.

Personally I would spring for the 4th wire (your equipment ground) in the feeder. I think you said your main disconnect breaker was 200 amps so if you didn't upsize the feeder to the house for voltage drop you will need a #6 awg copper wire for your equipment ground or #4 aluminum.

But your equipment grounds are connected to the grounding bar so any fault current imposed on them from a hot wire touching bonded metal will not be subject to this low impedance due to no bonded connection with the feeder neutral in the house panel. So what happens is the fault current tries to get back to the transformer thru the earth. For example for a fault current occurring on a 15 or 20 amp 120 volt branch circuit your probably going to be lucky if 4 amps flows thru the breaker if earth is your return to the transfomer. 4 amps will not trip a breaker and your panel metal and all wiring bonded to the fault will come to 120 volts.....very dangerous.

On the other hand if we give that fault current a low impedance path back to the transformer over copper and aluminum wire and bonded metal then enough amps will flow thru the breaker to trip it.

If you look at the diagram I posted you can see why that is going to happen.

Your other question about bonding the sub-panel fed with 3 wires is about the possibility of objectionable neutral current having a way to use other low impedance paths to return to the transformer when we bond neutral with the grounding system on the load side of the service disconnecting means. Neutral current can and will electrocute you and that possibility increases when we start bonding ground and neutral downstream of the service disconnecting means. Having any neutral current on the grounding system or bonded metal where it is not expected is extremely dangerous. For example you would not want current on your metal water pipes or tv coax etc...
Remember these are all connected to the electrical grounding system. So any bond neutral to ground load side of the main disconnecting means (service equipment) will potentially allow current to flow on those wires and bonded metal parts as it tries to seek its source (the transformer).
As long as those paths are high impedance ones and the feeder neutral in the 3 wires to your house panel does not open generally there is very little risk. The other issue is someone coming along and inadvertently constructing an alternate low impedance path and then connecting it to the grounding system. So as long as the grounding system is not bonded to neutral load side of the service equipment we drop the odds of neutral current showing up in areas we are not expecting it and that improves human safety.

The idea is to keep the neutral and ground bonding at one place in the system (SERVICE EQUIPMENT ENCLOSURE) and this simply reduces any chance that neutral current can find alternate paths to return to the transformer over grounding system connections.
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Old 07-24-2010, 11:15 PM   #22
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strange electric problem in new house, hot ground!


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Thanks for all the feedback. Although I still am very unclear how my "subpanel" is really any different than a main panel (other than the extra breaker at the pole) and therefore not allowed to bond the neutral by code.
.that breaker at the pole makes all the difference. The ground and neutral must be bonded at that disconnect. It also will be grounded via an grounding electrode system. now, see the explanations below.


Quote:
I don't see a physical difference between that or running a 4th wire all the way back to the neutral at the pole, other than there being a larger path back w/ the 2 wires.
the size is not of concern. The code requires certain size wire to be used.

so, how it is different:

3 wire: all current is carried on those 3 wires. The ground should not have any current flow on it so there should be no current that, via the grounding electrode system to possibly also flow on the other metallic conductors because they too are grounded.


if you bond the panel in the house, you have now made those other metallic conductors in a parallel connected run and actually connected to the neutral (though the grounding electrode conductor system) so they can carry not only fault current but current from any use that would be returning on the neutral because of your disconnect at the pole is grounded and those other conductors are likely grounded at the pole as well. So, due to that, you basically have made those extra conductors part of the neutral return path. You really don't want that for a variety of reasons.

So, 4 wire system:

the neutral and ground are not bonded at the house so the ground will not be carrying normal return current. The neutral will be carrying all the normal return current flow. That means even though the other metallic conductors are bonded to the equipment grounding conductor and as such, the equipment grounding conductor, none of them will be carrying any of the normal return current flow. They are not bonded to the neutral at the house.

now, they might carry some fault current flow but since that is an emergency system and is intended to be very short term, we don't really care.

Now, with your system, you have a neutral but the grounding system in your house isn't actually connected to anything other than the grounding electrode system. So, if you have a short to the equipment grounding system in the house, that current cannot return to the main transformer which is what is required to cause the breaker to trip on a ground fault condition. Granted, both the house and the pole are connected to a grounding electrode system at each point but the only connection between the two would be via the ground. The ground is actually a poor conductor and not, during a ground fault condition, you are asking it to be a good enough conductor to flow enough current to allow the breaker to trip and save your life.

It's late and I'm tired and I hope that makes sense but due to a fuzzy brain, I won't guarantee it at this point.
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Old 07-24-2010, 11:18 PM   #23
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Wow, a lot of information there, but I understood some of it. So, since the neutral and ground are bonded at my service equipment enclosure (pole breaker) then they can't be bonded in my main panel. Or are you saying no bonding should occur anywhere except at the service equipment enclosure. This is different that another poster who said neutral can be bonded in a panel that has no other means of disconnect. If I understand you right this is a safety precaution that has been added recently to most code. You also state that the 3 wire installation should normally be ok so long as the neutral doesn't open generally?? I'm not sure what you mean by that really. Why would any neutral open? Do you mean physically lose your neutral?
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Old 07-24-2010, 11:28 PM   #24
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strange electric problem in new house, hot ground!


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So, since the neutral and ground are bonded at my service equipment enclosure (pole breaker) then they can't be bonded in my main panel
right

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. Or are you saying no bonding should occur anywhere except at the service equipment enclosure.
same thing. Your disco at the pole is your service equipment enclosure

Quote:
This is different that another poster who said neutral can be bonded in a panel that has no other means of disconnect.
no. it is the same thing I said. I said the disco at the pole is why you need the 4 wire to the house.


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If I understand you right this is a safety precaution that has been added recently to most code.
actually it has been there for many years. They both used to be in the code. They simply removed the allowance of the 3 wire feed.
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Old 07-24-2010, 11:39 PM   #25
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strange electric problem in new house, hot ground!


Area 123

Here is a drawing giving you an example of a dangerous possibility if we bond neutral and ground at a sub-panel. The drawing is a service equipment load center with a 3 wire feed to a detached building sub-panel that has a bonded neutral with ground.. The home owner has decided to run a water pipe to the detached building and he decides to connect the water pipe to the grounding electrode system like he sees done at the service equipment back at the house.

The thing to remember is current seeks the transformer source and it will take any path available to get there. In the drawings case you could have 1/2 the neutral return current using the water pipe because of the low impedance.
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Old 07-24-2010, 11:44 PM   #26
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right

same thing. Your disco at the pole is your service equipment enclosure

no. it is the same thing I said. I said the disco at the pole is why you need the 4 wire to the house.


actually it has been there for many years. They both used to be in the code. They simply removed the allowance of the 3 wire feed.
Ok, my last round of questions before bed.. What if there was no disconnect at the pole, which seems to be a more common method by the power companies. Then could I have a 3 wire feed and bond inside my panel safely? Sorry if you already answered that, it's late and I might have missed some posts.

Would it be as simple as asking the power company to remove their breaker & connect the feeder directly like my last house was done? My panel has it's own 200 amp breaker anyway.

(rhetorical question) why would the dummy install a disconnect and sell me a 3 wire feeder??? And why would my electrician not know to add the 4th wire after the disconnect???? (not rhetorical) Until we figure out how to add a 4th wire if we have to, isn't is safer to have the neutral bonded so that there is a path back to the transformer if needed? At least this way my neutral would not become hot w/o tripping a breaker, right? or am I way off.
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Old 07-24-2010, 11:59 PM   #27
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You also state that the 3 wire installation should normally be ok so long as the neutral doesn't open generally?? I'm not sure what you mean by that really. Why would any neutral open? Do you mean physically lose your neutral?
Neutrals can open for many reasons, corrosion, loose connection, unnoticed cracked lug that eventually fails, damage etc... it happens more than you might think. My point was that 99.9% of neutral current uses the neutral to return to the transfomer ... if you would have an open neutral event then all the neutral current that was using the neutral will now seek another way to get to the transformer. So due to the bonding to the grounding system it now can potentially start flowing on the grounding system in dangerous amperages because it lost its low impedance path back to the transformer. You notice weird things with the electrical and what would be your first place to look? Not knowing that the panel metal is energized with neutral current. You may get away with touching the panel or you may not.
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Old 07-25-2010, 12:09 AM   #28
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Why would the dummy install a disconnect and sell me a 3 wire feeder???
Because they may allow it in our jurisdiction and it may be the standard installation because they are not going by the 2008 NEC but an earlier code cycle.


Quote:
And why would my electrician not know to add the 4th wire after the disconnect???? (not rhetorical) Until we figure out how to add a 4th wire if we have to, isn't is safer to have the neutral bonded so that there is a path back to the transformer if needed? At least this way my neutral would not become hot w/o tripping a breaker, right? or am I way off.
Your electrician should have realized that with only 3 wires feeding your house panel you would need neutral and ground bonded in order to have protection against ground fault especially with an isolated ground bar. If he is the one that connected your dryer neutral to that grounding bar then he may be very inexperienced or very tired or needs to learn a thing or two..

Quote:
Would it be as simple as asking the power company to remove their breaker & connect the feeder directly like my last house was done? My panel has it's own 200 amp breaker anyway.
I would stick with the remote disconnect ...lets you get the entire panel deenergized if you ever want to work in it to add circuits.
The 200 amp disconnect in your panel is required. You must have a service rated disconnect located at your house.

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isn't is safer to have the neutral bonded so that there is a path back to the transformer if needed?
Yes but only if you do not have another conductive path like I'm showing in the previous diagram with the grounding system. But if 3 wire is not compliant with local codes you will need to get the 4th wire and unbond the panel. In your case it would be unlikely to have a parallel conductive path do to the type of installation.

Do not land any neutrals on that grounding bar ... equipment grounds only even if you bond it.
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Old 07-25-2010, 08:07 AM   #29
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Do not land any neutrals on that grounding bar ... equipment grounds only even if you bond it.
Yes, I only have grounds on the ground bar and neutrals on the other side. I think for now I have to bond the neutral to be safe. THe next step will be to go over your diagram and all the other posts closely, and talk to my electrician and the power company and see if this type of installation is allowed and safe.
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Old 07-25-2010, 11:29 AM   #30
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I just had a thought. I already have a large copper grounding wire going from my panel to the outside. I think it goes to a grounding rod but I could be wrong, I can see the rod but I'm not sure which wire is going to it. Could that copper wire be used to go all the way back to the pole as the 4th wire? Could it be broken or could the electrician forgot to connect it back to the pole? If that is the grounding rod it goes to, could that copper be spliced and sent all the way back to the pole as a safe fix?

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