Neutral

Why is the Neutral piggybacked on the side of the disconnect?
Is there some reason why the switch is not built with four poles?

The general practice in my plant is never to have the neutral wire go through an overcurrent protection device or disconnect switch. This is mainly to prevent ground fault issues.

I think the 2002 NEC Article 240.22 allows for the neutral/grounded wire to go through an overcurrent protection device IF that device opens all conductors of that circuit...

It's just Telemecanique don't make a 4 Pole Isolator in that range (VCCF), so you have to seperately attach Aux contacts and Neutral poles.

You need to ask Telemecanique Why!!

Yes I know never to fuse a neutral, I was just wondering if there is any significance to the fact that it is on the side of the disconnect that way?

Thanks

Let me see if I can make sense.

One the neutral is not nor should not be a current carrying conductor...we all know that it may BUT using theory etc the neutral should not carry current, therefore does not need to go thru an over current protection device...ie breaker, fuse etc.

WHY...simple, keeps all wires together in one location. I like the idea of having the neutral "piggybacked" or on a connector beside the main breaker. This allows for easy access to ALL incoming power wires that are in close proximity for testing.

It is also possible that it is an IEC standard, you mainly see that with machines built in Europe. I dont have a copy of IEC standards so can not say for sure.

Thanks Ron
This was definitely built for Europe
We just got it going 415V 50 Hz motor we are running it on 480 Volts 60 Hz.
We'll see how long it lasts.
The 55-0-55 Txfmr didn't work, so we scabbed in 120V for testing and it works great.

The layout you have shown is, as stated, an IEC unit. The only reason they used a 3- pole unit and not a 4-pole unit is because that is what they had access to at the time of installation. Many manufacturers have 4 pole disconnects available for this purpose.

Our NEC electrical code does not typically require disconnecting of the neutral conductor. The only application, that I know of, where it is required is on the power to a gas dispensing pump. The code requires a disconnect that simultaneously disconnects the ungrounded and grounded conductor. It does however allow for the disconnecting of the grounded conductor as long as it is done simultaneously with the ungrounded conductors. Approved handle ties are acceptable. It is typical that you would not disconnect the neutral (or grounded conductor) when disconnecting the ungrounded conductors.

The neutral wire is designed to carry the unbalance between phases. When that is all that it does it is not considered a "current carrying conductor".

In a 3 phase, 4- wire, wye connected service a common conductor carries approximately the same current as the line-to-neutral load currents and is considered a current carrying conductor. Also in the same wye configuration where the major portion consist of non-linear loads the neutral is considered a current carrying conductor. See NEC 310.15 (B) 4, which outlines this in detail.

It is quite common to use a 4 pole ATS for emergency power generator systems. It is also quite common to see 4 pole on the generator side and 3 pole on the mains side.
beerchug

If a switched neutral is required, I actually like the idea of a separate contact for the neutral. Notice it's even marked 'N' so there's no confusion!...

If a 4-pole disconnect was used, you might have to 'figure out' which wire was the neutral. Especially since there's no identification on the wires!...

In other words, if these wires were going through a standard 4-pole disconnect, my first guess as to which wire was the neutral would NOT be that B-L-A-C-K wire!...

beerchug

-Eric

Eric, if it were done properly to code, you would have no confusion as to which wire was the neutral. It would be color coded.

Why would anyone want to disconnect the neutral in a control panel feed anyway? (better question is why was system set up for need of this neutral?) The neutral is (should be) bonded to the ground system at its source. If the ungrounded hots are disconnected, what harm would the neutral cause? I think the greater potential harm would be in loosing the neutral while the hots are still connected.

Something must be a line-to-neutral load (120vac USA or 230vac in Europe)within the system for them to have installed a grounded conductor in this 3 phase panel. If you loose the neutral (say by a malfunction in the added handle tie) you could burn up lots of electronics. The code allows handle ties but, the obvious first choice (IMHO) should be a disconnect with permanently attached disconnecting means between all four poles. Just my two cents.

g.robert said:

Eric, if it were done properly to code, you would have no confusion as to which wire was the neutral. It would be color coded.

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As far as I am concerned, that IS colour coded correctly. George stated that this was a European build, it's more than likely British. George also stated that the machine was built with a 415v 50hz motor, that is definately British, not European, as they used to use 220/380v before we all harmonised and now use 230/400v. The British dropped their quoted supply voltage by 10v (240v to 230v) and mainland Europe upped their voltage by 10v (220v to 230v).

The phases are coloured Red, Yellow and Blue, in that order and neutral is Black, which,as far as us Brits are concerned, is perfectly correct.

Paul

Hi Group, I ran into a strange one last week that had me pulling my hair out, I even called Ron for his help...
The power feeding the kiln lights at our plant in Nashville comes from a 480 delta to 208/120 wye,4 wire transformer. In checking things out, I found 116 volts from neutral to ground...so I pulled the breakers out of the panel, and found 116 volts still on the neutral, and on the CB's that were now hanging out in space. I checked the neutral bar, and noticed that it was not bonded to ground, so I pulled the power feed to the transformer ,and I still had 116 volts from the neutral to ground. I then started to remove a few wires from the neutral bar so that I could connect the bonding link...the first wire I pulled off arced as it came out, and when I checked the bar to ground it was 0 volts...what had been done was that someone had run some 480v wires up to a new set of 277volt lights way up near the top of the silo area, and had just hooked up the return to the nearest place they could find, which was this ungrounded neutral bar. After bonding the bar, everything returned to normal.
Someone's stupidity could have killed someone. There was enough current flowing thru that line that I found 4 places where the neutral wires had been melted out in the kiln.

Thanks for the help Ron.

I know that there are certain times that code stipulates that you cann't bond a neutral to ground, as in a residential subpanel, but please, make sure to bond the neutral on these transformer setups if code will allow it. The life you save might be your own.

David beerchug

The phases are coloured Red, Yellow and Blue, in that order and neutral is Black, which,as far as us Brits are concerned, is perfectly correct.

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Maybe depends who you are building your panels for. We've been building systems for about 3 years now, and probably only built about 2 or 3 with that particular phase colouring (and they were defined by the customer). Unless we are instructed otherwise, we tend to stick to the EN 60204-1 colour scheme.

I know the Water industry insist on the traditional Red, Yellow and Blue colouring, but they have their own regulations (WIMES).

In the EN 60204-1 system, the Neutral is actually light BLUE, not BLACK.
Just my opinion!

As far as I am concerned, that IS colour coded correctly.

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Then you would have had no problem determining which wire was the neutral and my point is proven correct.

I know that there are certain times that code stipulates that you cann't bond a neutral to ground, as in a residential subpanel, but please, make sure to bond the neutral on these transformer setups if code will allow it. The life you save might be your own.

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Not only are you allowed to bond transformer neutral to building grounding system, you are required to do so. The connection is covered in the NEC (for USA installations)and is termed "separately derived system". As for sub panels you are not to bond neutral to ground. That should have been done at or close to the source.To bond neutral to ground in a sup panel could create hazard if incoming neutral wire connection is ever lost.

Eric, if it were done properly to code, you would have no confusion as to which wire was the neutral. It would be color coded.

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Even following NEC the neutral wire may be black if marked, the connection block is marked.