Neutral on Earth Bar

It is unlikely to cause a shock, as generally neutral-to-earth voltages are usually so close. Its need to be connected there or not depends upon the earthing system at the facility: is it TT, TN-C, TN-S or TN-CS?

If your ground system is compromised somehow (i.e. high resistance) and neutral-ground bus isn't joined you lose some protection from electric shock and fire. So no it is not dangerous. (it would help to describe your system in more detail because I am speaking about typical residential setup)

I believe a connection of a neutral on the equipment ground bar would be at high risk of electric shock. The 1-phase current on the neutral trying to return to the source would be allowed to flow upon (energize) any metal case (panelboard, conduit, etc) that you have also bonded to the equipment ground bar. So upon touching it, you may receive a shock.

The neutral is part of the electrical circuit (path). An earth is intended to channel away stray or accidental current safely to ground. Imagine if you connected a hot wire to a light bulb and the common to a wire stuck into the ground. You would get nothing. Now take an electric motor with two wires, a hot and a neutral. If the hot were to short out to the case of the motor, the current would be led to ground through the case. Neutral and ground(earth) are sometimes tied together in some communities, but only at one point which is at the service entrance.

Correctly done at the correct point it provides significant improvement in safety.....

Its not for amateurs to decide to do.....

Actuall neutral or star point of the transformers are earthed or grounded. such is approved by the power authority and only in power sub stations. After such approved places Neutral earthing can only be allowed were Protective Multiple Earthing (PME) Is allowed or practiced.

Yes, it can cause shock if some of the metal works associated with the system is not bonded to the neutral and also if the is a break in the neutral line.

PME or Neutral earthing is not recommended for domestic duellings as it could be dangerous to live. The essence of praticing PME is to keep the earth fault loop path as low as possible as to enable tripping of protective devices and it is done were it is not possible to achieve the desired earth electrode risistance value.

Dickson. Abuja Nigeria

Hello to all.

I would like to know why you want to fix the neutral to an earth connection?

Is it because you have a three phase supply to something, and wish to connect equipment of a single phase but have no neutral?

If so then do not do it, much safer to bring in a new supply, or fit an isolating transformer, and then put in local protective devices.

Dave.R

You appear to think slightly backwards about this. Let me run it by you again....

True three phase equipment does not need a neutral. So the original question had nothing to do with 3 phase equipment, it refers therefore to single phase equipment only.....

Single phase equipment does need (in those countries with a nominal 220-240 volt supply) to have a neutral connection as phase to phase is too high (415VAC?).

It is also perfectly feasible to have single phase and 3 phase equipment on the same mains supply, provided loads are placed reasonably carefully...and of course the neutral is earthed at the correct point, usually the sub station.

The earth neutral connection is needed only to provide a path for a fault current in the case where the earthed chassis of any equipment (PC, washing machine etc) is accidental connected to the phase as well. If there was no neutral earth bus bar connection at the sub station, no/or little fault current could flow and anyone touching the chassis might get still get electrocuted.

I am less sure of the safety aspect when 3 phase equipment gets a short to ground and the effect of the neutral to ground connection, but I could well imagine that a higher current flows and unbalances the phases....but I would prefer to leave that item for a qualified electrician/engineer to answer in detail.

I forget what current is needed to kill a person, but it is only milliamps if I remember correctly, not even amps!!!

So a fuse might not blow due to the extra current on its own....

A further stage of safety is/can be achieved by adding Earth Leakage trip breakers to the incoming phases/neutral/earth from the substation. Touching mains (still a painful experience believe me!) with such equipment installed shuts down that phase within a few microseconds (been there, done that and NOT got the T-Shirt!).

I am renovating a house for my daughter and future son-in-law that was built around 1960. I was amazed to see that in 1960 they still have the old 2 wire system here in Germany in that part of the house, (the house was added onto about 30 years ago and that was done with three wire connections)....

We are pulling 3 wire cable in all over to fix that asap.....Big job!!

The UK used a 3 wire system called BS546 if I remember correctly, up to 1946(?) when the Ring main system first came out with its shuttered (mostly switched) sockets. A minor change came I believe at the beginning of the 1970s when the pins had to be partially insulated.

This to my mind is probably the safest system around using nominal 220-240 VAC. The added ELCBs (70's?) also made things still safer for all users......

Germany (and most other European countries too) has a lot of catching up to do with regards to electrical safety.....in older properties only 2 wires, no idea where the phase is in many of these countries on the socket and no law for fitting ELCBs.....WOW!!

The question only refers to a neutral being connected to a earth bar, it could be any neutral, even equipment that requires thee phase and neutral, I have come across that in the past.

Some old three phase supply boards did not have a neutral bar in them so you could not put out a single phase supply from them, and after forty years or so the earth may not be as good as it should be, If you connected a neutral to the earth bar in one of these you would be asking for trouble.

I cannot see why if it was a single phase supply that you would want to connect the neutral to an earth connection, much better to place it where it should be.

The only supply that you could get away with this would be A TN-C system where the neutral and earth conductor are combined all the way to the consumer unit, even then the neutral should still be in its correct location.

Dave.R

You wrote:-

I cannot see why if it was a single phase supply that you would want to connect the neutral to an earth connection, much better to place it where it should be.

The reason is simple (I have also posted it at least once), is if you have a piece of equipment that has a metal frame, in 99% of the cases it must be connected to ground.

If a failure occurs and phase makes contact with the frame for some reason, the frame goes to mains voltage.

If ground is not connected to neutral, there is either no path for the electrons or only a very high resistive path via the frame, via the ground in the cable to the neutral. Little current would flow and no fuse would blow, so the frame remains at phase voltage....now would you want that to happen ion your house?

With the neutral to earth bonding in the substation, there is a clear low resistance path that will cause high currents to flow and fuses to blow.

If you also had an earth leakage trip breaker installed, the ELCB would trip even if a high resistance contact happens between phase and earth, like a human being for example, which makes a house far safer for its occupants.....

Make yourself a simple drawing if you still do not understand it, sometimes pictures speak louder than words.....

Andy,

I already know what the earth bond is for, What I am saying is that it is not for the consumer to place neutrals on earth connections. That is for the energy supplier to do so either at the sub station or any place before the point of consumption, get it right, neutrals go to neutrals and earths go to earths, it does not matter once it connects to the supply, but you will not get a pass certificate for doing it in the consumer unit.

AT NO POINT IN ANY OF MY POSTS and to the best of my memory, anyone else's either, did we mention anything other than bonding neutral/earth at the substation.

So why are you now brining it up? Whats the point you are trying to make?

If there was a post that mentioned this (other than your last) please be so kind as to supply the post #.

Thanks in advance.

Sorry for the delay, have not been able to get back till now.

The point I am trying to make is that not in all instances is it safe to join a neutral to an earth connection if there is a chance that it allows equipment to become live, it depends on the position and the supply type, the questioner did not specify where exactly.

I have just found some info on the net that goes into greater detail earth and neutral arrangements.

I hope that this is found useful http://en.wikipedia.org/wiki/earthing_system

If in doubt, consult a qualified electrician.

In the USA,The neutral and ground rod are required to be bonded together.At the main panel, the Equipment Grounding Conductor must be bonded to the neutral in the panel.Subfed panels should not have the Equipment Grounding conductor bonded ( Such as mobile homes, etc)

This is per NEC

look at the above site under the heading Regulations.

IN the USA and Canada.

The neutral must be connected to the earth (ground) conductor ONLY on the supply side of the customers disconnecting switch. Additional connections of neutral to ground within the customers wiring are prohibited.