I?m looking for some information; I have a situation on some product designed to be used with independent neutrals. In the field this was modified to have a shared neutral placed in the system. This is a modular system designed for three hots, three neutrals and two grounds. The argument is running three hots with only one neutral using number 10 rather then #12 then jumpering the neutral to the three (all of which are #12?s) in the system now making them a shared system. Now what is being said is the service conductor for the building has only one neutral so in reality everything shares a neutral. So if they run one or three neutrals to the consolidation point it accomplishes the same thing. I say it doesn?t as the rest of the system was not sized to have this done. I need some help on this as a result of this the systems seems to of failed and fried some equipment. Now my contention is if the proper neutrals had been installed the smaller neutrals (#12) would have been able to handle the loads they were intended to handle. Thus nothing would have happened, as it is they say they lost a neutral and ended up with 208v going through a receptacle. Any comments? I need something I can use to defend my position and I don't seem to be doing alot of good with logic and math I could use some reference matterial to enter into this if I'm wrong I'm wrong and I would live with it but as it stands I only learned of this as a result of the problem but there are a few hundred more spots where this was done (to cut costs) I'd like to find a way to show them it may happen again if you don't go to the intended method of wiring for the device.
Shared vs indepenant neutrals
- Thread starter gardiner
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- Massachusetts
Re: Shared vs indepenant neutrals
I am not sure what your question is, are you talking about prewired office furniture?
If so it has been my experience that if the customer took the time to get the furniture with separate neutrals (it costs more then multiwire furniture) they expect the branch circuit feeding it to have separate neutrals also.
You can get "home run" cable that has 3 - 2 wire circuits for this.
Usually this is done to prevent problems with harmonic loads.
[ May 02, 2003, 09:49 PM: Message edited by: iwire ]
I am not sure what your question is, are you talking about prewired office furniture?
If so it has been my experience that if the customer took the time to get the furniture with separate neutrals (it costs more then multiwire furniture) they expect the branch circuit feeding it to have separate neutrals also.
You can get "home run" cable that has 3 - 2 wire circuits for this.
Usually this is done to prevent problems with harmonic loads.
[ May 02, 2003, 09:49 PM: Message edited by: iwire ]
Re: Shared vs indepenant neutrals
Gardiner, I don't think the single # 10 neutral would have a bearing on your problem.
The # 10 feeder neutral would have had to have been lost affecting all three circuits.
I may not be understanding your description correctly, and if this is the case I apologize.
You may be intersted in this thread. http://www.mikeholt.com/codeforum/ultimatebb.php?ubb=get_topic;f=12;t=000033
Roger
Gardiner, I don't think the single # 10 neutral would have a bearing on your problem.
Loosing a neutral (one of the original three grounded conductors) would only mean an open on one circuit, and couldn't have resulted in a series across any of the three circuits.
The # 10 feeder neutral would have had to have been lost affecting all three circuits.
I may not be understanding your description correctly, and if this is the case I apologize.
You may be intersted in this thread. http://www.mikeholt.com/codeforum/ultimatebb.php?ubb=get_topic;f=12;t=000033
Roger
Re: Shared vs indepenant neutrals
....I need some help on this as a result of this the systems seems to of failed and fried some equipment....
The problem could be that you have a DELTA trans tap. When it is thought to be a Y tap. This gives you a high leg. (208) Check to be sure.
....I need some help on this as a result of this the systems seems to of failed and fried some equipment....
The problem could be that you have a DELTA trans tap. When it is thought to be a Y tap. This gives you a high leg. (208) Check to be sure.
Re: Shared vs indepenant neutrals
My problem with this entire business is I'm 2000 miles away from the problem. The electrician that ran the wires is convincing the customer it doesn't matter in any way shape or form if you have a shared neutral or a dedicated one since he says they only run one neutral to feed the service in the first place. Now I really don't have a problem with replacing the unit which I am doing to be safe. But my problem with it is he should not of modified it and to get to the other two hundred units he did this to and put them the way they were designed before something happens more serious then this. Next problem is I haven't figured out how an electrical inspector could allow someone to rewire a premanufactured device which would invalidate its UL listing and pass it. Now rewiring one and getting it by the inspector yes but two hundred? So I need something I can use a layman might be able to understand to fix the problem I wouldn't want to void the warrenty its not the customers fault he is listening to someone he most likely knows I am against it being said the equipment managed to damage other sensitive equipment when in it is not really its fault it may be at fault.
My problem with this entire business is I'm 2000 miles away from the problem. The electrician that ran the wires is convincing the customer it doesn't matter in any way shape or form if you have a shared neutral or a dedicated one since he says they only run one neutral to feed the service in the first place. Now I really don't have a problem with replacing the unit which I am doing to be safe. But my problem with it is he should not of modified it and to get to the other two hundred units he did this to and put them the way they were designed before something happens more serious then this. Next problem is I haven't figured out how an electrical inspector could allow someone to rewire a premanufactured device which would invalidate its UL listing and pass it. Now rewiring one and getting it by the inspector yes but two hundred? So I need something I can use a layman might be able to understand to fix the problem I wouldn't want to void the warrenty its not the customers fault he is listening to someone he most likely knows I am against it being said the equipment managed to damage other sensitive equipment when in it is not really its fault it may be at fault.
- Location
- Massachusetts
Re: Shared vs indepenant neutrals
Hi gardiner,
What exactly do you mean by rewiring?
Did he actually change anything inside the unit?
This would void any UL listing.
Or did he just group all the neutrals together at the point you tie the equipment in.
If the electrician ran 3 "hots" from separate phases and one neutral this would be code compliant but still might not meet job specs.
Hi gardiner,
What exactly do you mean by rewiring?
Did he actually change anything inside the unit?
This would void any UL listing.
Or did he just group all the neutrals together at the point you tie the equipment in.
If the electrician ran 3 "hots" from separate phases and one neutral this would be code compliant but still might not meet job specs.
Re: Shared vs indepenant neutrals
Thanks for the replies, I would love to drop it on the design engineer unfortunately the design engineer and myself are involve in this as I'm the one who speced the device in the first place and he is the one who invented the device. We are just trying to find ways of solving this without having to resort to violation of UL listing as in most cases we have found over the years the client usually takes it we are just covering up and not addressing the problem. I'd rather just be able to say you had terminal strips prewired for a specific system a system designed to handle one #12 neutral for each hot, running one #10 to handle 3 hots defeats the idea of the system, then on top of that you can't come to me after complaining a neutral failed and saying its my fault when you changed the entire idea of the system in the first place. The items were not connected to any modular office furniture just for the sake of clarity they were connected in a floor box with two receptacles in it these receptacles were fed from the device that came prewire to connect to this box. I'd just like to handle this without going into hurting the electrician who I really believe thinks he did nothing wrong I'd rather educate then slap someone on thr wrist any suggestions would be apprieciated.
Thanks for the replies, I would love to drop it on the design engineer unfortunately the design engineer and myself are involve in this as I'm the one who speced the device in the first place and he is the one who invented the device. We are just trying to find ways of solving this without having to resort to violation of UL listing as in most cases we have found over the years the client usually takes it we are just covering up and not addressing the problem. I'd rather just be able to say you had terminal strips prewired for a specific system a system designed to handle one #12 neutral for each hot, running one #10 to handle 3 hots defeats the idea of the system, then on top of that you can't come to me after complaining a neutral failed and saying its my fault when you changed the entire idea of the system in the first place. The items were not connected to any modular office furniture just for the sake of clarity they were connected in a floor box with two receptacles in it these receptacles were fed from the device that came prewire to connect to this box. I'd just like to handle this without going into hurting the electrician who I really believe thinks he did nothing wrong I'd rather educate then slap someone on thr wrist any suggestions would be apprieciated.
hbendillo
Senior Member
- Location
- South carolina
Re: Shared vs indepenant neutrals
I realize you may have solved this issue but I found it interesting. The electrician telling the person that using individual neutrals does not matter because the service is run with only one neutral is pretty funny. One does not have anything to do with the other. Small circuits at the branch circuit level connected to loads with high harmonic content are more problematic than you would normally see at the service neutral. Most buildings have many other loads that have neglible harmonic content so that the additional neutral load that the service sees does not have the impact on it like the aformentioned small branch circuit. However, the service neutral may need to be oversized depending on the total amount of harmonic load on the system. The manufacturer of this product apparently had problems in the past and wanted to make sure that neutrals had no chance of overheating. On the face of it, it seems that what this electrician did was very irresponsible. However, are you saying that the product itself experienced the problems are did the wiring cause problems elsewhere in the system.
I realize you may have solved this issue but I found it interesting. The electrician telling the person that using individual neutrals does not matter because the service is run with only one neutral is pretty funny. One does not have anything to do with the other. Small circuits at the branch circuit level connected to loads with high harmonic content are more problematic than you would normally see at the service neutral. Most buildings have many other loads that have neglible harmonic content so that the additional neutral load that the service sees does not have the impact on it like the aformentioned small branch circuit. However, the service neutral may need to be oversized depending on the total amount of harmonic load on the system. The manufacturer of this product apparently had problems in the past and wanted to make sure that neutrals had no chance of overheating. On the face of it, it seems that what this electrician did was very irresponsible. However, are you saying that the product itself experienced the problems are did the wiring cause problems elsewhere in the system.
Re: Shared vs indepenant neutrals
If the items were fed with 3 hots and 3 nuetrals and then you had a conection point to feed 2 recpt. With that type of conection if the neut. is lost or not conected properly then you would have 208 to the outlets. If this is not a UL or listing thing then I would not know how you can not want to slap the electrcian for this. I agree with hi9s point that the building service only has one nuet. What happens when you lose that one? Would be a question that I would ask him. If your specs and equipment call for 3 hots and 3 neuts. how can someone in the feild make a modification without accepting the risks?
You say he modified the equipment, can you eleborate as to how? Did he just take 3 neuts and tie them together in a j-box as was previously asked. Are all of his cicuits that come to the equipment coming from differant phases? That would be a code violation.
In order to geve more of an opionion we need more information.
If the items were fed with 3 hots and 3 nuetrals and then you had a conection point to feed 2 recpt. With that type of conection if the neut. is lost or not conected properly then you would have 208 to the outlets. If this is not a UL or listing thing then I would not know how you can not want to slap the electrcian for this. I agree with hi9s point that the building service only has one nuet. What happens when you lose that one? Would be a question that I would ask him. If your specs and equipment call for 3 hots and 3 neuts. how can someone in the feild make a modification without accepting the risks?
You say he modified the equipment, can you eleborate as to how? Did he just take 3 neuts and tie them together in a j-box as was previously asked. Are all of his cicuits that come to the equipment coming from differant phases? That would be a code violation.
In order to geve more of an opionion we need more information.
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