Tying Neutrals together from separate circuits

Merry Christmas
Status
Not open for further replies.
L

lottalliance

New member
I am running some control power from a transformer in a VFD that is 480v primary 120v secondary to a control circuit in a cabinet and have been instructed to tie my neutral in to an existing daisy chain of neutrals from a UPS that is a completely different circuit and power source.

I have always been taught that it is good practice to keep your neutrals separate when coming from two different power sources. I am looking for some clarification. Thanks for any help
 
This would be a violation since the neutrals would be paralleled art. 310.4

Also this install would create very high EMF's
 
If you tie your circuit #1 into the neutral from circuit #2 the there will be no path back for the current back to the source of circuit#1. Current will always find its way back to its source and will therefore try to get there by whatever means. This means could be a ground bus or some other common connection between the two circuits. This is undesireable since it would introduce current on the ground system or in some other area where it shouldn't be.
 
Dont do this.

Some electrician did this in my home to save running the correct number of cores and I got a belt whilst changing a wall-lamp from current passing through a neutral that shouldn't be.
 
Last edited by a moderator:
dbuckley said:
Dont do this.

Some electrician did this in my home to save running the correct number of cores and I got a belt whilst changing a wall-lamp from current passing through a neutral that shouldn't be.
Click to expand...

Is that word really appropriate?
 
Last edited by a moderator:
Thanks glene,

That was nice.
When I read your comment, in my mind, the loud booming voice from the old movies stepped in. Some how "Do not" also magically turned into "Thou shalt not" and some "iths" got thrown in.

Something like...

Lott,
Thou shalt not intermixith the circuit neutrals,
and
Thou shalt not crossith over the power sources.

You are headed for electrical problems,
and code violations.
 
Do not mix neutrals from different sources not only is it a code violation but it is dangerous to both the homeowner and an electrician working on the system it is an electrocution hazzard. Whoever holds the license in your company is liable for any problems. Dont make a big deal about it but politely refuse as you may also be liable if it is proved that you knowingly commited this violation and someone got hurt. Such as a thread coming back to bite you in court.
 
quogueelectric said:
Electro motive force or Electro magnetic fields?? TLA confusion!
Click to expand...

In my experience EMF has "always" refered to Electro motive force. But our English language seems to change almost daily anymore, who knows what it means this week.

I can't help but think you're somehow connecting this with EMP though.
 
Sorry Dennis, when I first read the thread I didn't notice the connection between the two posts.
 
I know that some here have heard me say this before, but you will hear it again.

When an inspector says one cannot install something, you guys here in general will get upset/mad that he does not provide a code section.

Well, I have seen several in this thread say the item in discussion is a code violation...what section(s) of the NEC is this a violation of, if it even is an actual violation?


Is this even a dangerous installation?




[I am not disputing this, I would like to see more information and code sections to help with the general trend in answers]
 
Thanks Pierre

I was wondering the same thing

There are many times we will connect neutrals of one system to neutrals of other systems, transformers are one point where this is even required by code.
(I.E. primary to secondary)

What about in control panels where control transformers have one side of the secondary bonded to ground, this will have many neutrals connected together if there are many control transformers???

But if the above is done where the secondary conductors leave a control panel, then bonding the neutrals together can set up parallel path with the bonding of the neutral at each power source, This can have adverse effect on any electronic I/O's type control systems
 
Last edited:
Pierre C Belarge said:
I know that some here have heard me say this before, but you will hear it again.

When an inspector says one cannot install something, you guys here in general will get upset/mad that he does not provide a code section.

Well, I have seen several in this thread say the item in discussion is a code violation...what section(s) of the NEC is this a violation of, if it even is an actual violation?


Is this even a dangerous installation?

[I am not disputing this, I would like to see more information and code sections to help with the general trend in answers]
Click to expand...


300.3 comes to mind.
 
physis said:
Pierre C Belarge said:
When an inspector says one cannot install something, you guys here in general will get upset/mad that he does not provide a code section.
Well, "I don't like it" isn't sufficient. That's why we use codes as a quasiuniversal language.
Click to expand...


I am playing 'devil's advocate'.


So what code section(s) will you post? or Is this not a permitted installation?;)
Click to expand...
Click to expand...
 
Status
Not open for further replies.
Top