ECN Forum Forums Code Related Discussion Canadian Electrical Code Topics do I need a neutral conductor?

I am a Canadian inspector.

Based on the 19th edition of the CEC, a neutral would not be required in this instance.

The XO connection of the transformer being installed must be connected to the ground electrode via a copper conductor meeting the requirements of table 17.

I forgot to mention that a bonding conductor meeting the requirements of table 16 is also required for the transformer case and raceways.



[This message has been edited by Rick Kelly (edited 06-12-2006).]

I too am a Canadian Electrical Safety Officer for 10 years.
I appreciate that it is possible to supply the second building without needing to bond the neutral as you would have to at the first building. I did not say the neutral was needed unless it is also bonded to the enclosure as it is required at the service interfacing with the utility but I am saying it is still required. But you have the option of establishing a new service at the second building and that would require a grounded circuit conductor from the first building.
10-204(2) may be primarily to ensure that contractors provide a grounded circuit conductor for services where the Hydro transformer has a Y connected secondary. BC Hydro has been phasing out delta secondary services so almost all of their distribution is derived from a grounded system.
By extension it has been the policy of this office to also require a grounded circuit conductor to every building supplied from the one with the Hydro service. In addition there is the need for a system ground for each new system like the secondary of a 600/ 120/208 transformer. In a hospital here we have a substation supplying the entire campus. All the distribution feeders are 600 volt and at least 1 building is 1000 feet from the source. calculate the impedance of a bonding conductor 1/0 on a 800 amp 600 volt carrying the fault at the second building. Now do it again with a 3/0 neutral (no smaller than the required system ground) Plus a 3/0 system ground per the engineers spec.
In the case of the hospitals ditribution, the neutral is grounded at each building and the system ground is extended to each building effectively providing a parallel path for faults ahead of the forst transformer and in the primary of those transformers.
Yes I know the argument is the system ground establishes a fault return and that the neutral does not carry any current unless it is also bonded to the second building enclosures.
This interpretation has been challenged and supported many times over the last 16 years that it has existed. It has been supported by professional engineers and by the utility too. I don't think I will change my mind based on any of the arguments offered so far. My opinion is also based on the 19th edition of the cec as well as the 16th edition and perhaps even older code books too. Now if the 600 volt service from Hydro was a 600 volt Delta then I'll be looking for the ground detection lights.
In answer to rewire I might not connect the neutral to anything at all but in my scenario at the hospital it is connected at the enclosure through a bonding jumper. If the building housed livestock it would be required to bond the neutral.

If you were to actually use the bonded neutral on a 347 volt load, would the parallel ground not carry a substantial part of the load? I would think that it would trip the primary ground fault protection.

What it sounds like to me is that, in the case of an actual ground fault, you are reducing the effectiveness of the ground fault protection by providing a parallel neutral path for the fault current.

If you want a better ground return, the code should require a larger ground. If you want to defeat the ground fault protection, use the neutral as a ground, IMO.

Mikesh Welcome to the ECN forum...Glad you found us
Any idea when we might see amendments on the CEC 20th ed and when it will be adopted for British Columbia

Thanks

What seems like a pretty straightforward solution turns out to be quite complicated. I have seen numerous instances where a 3 wire 600 volt primary feeds a 120/208 volt 4 wire system. Mikesh refers to 10-204, which specifies services, so would this apply here? Also, low impedence path for fault current from phase to ground on the primary feeder should be provided by the bonding, which is connected to the neutral on the 600 volt system. From what I understand, Mikesh is proposing using the neutral as a second bonding conductor but I could be misinterpreting here. If the minimum required bonding conductor is not adequate to interrupt fault current, maybe the rule needs to be reviewed.

TWH raises a hugely important point when the service is ground fault protected and any other building on the system must have its' power distribution designed with this in mind. I recall the local coast guard station had a problem with a ground fault in the second building tripping the main. The solution was to remove the fuse for the O?C protection relays. That resulted in a failed overhead transformer and nearly cost an electrician some hospital time when a wire sock fell over the main bus.

Secondary buildings can be wired as extensions of the main service and do not necessarily have to be grounded at the second building (some exceptions). If the choice is to establish a new ground the ground fault protection scheme and the instrumentation to protect the serce equipment must also be designed to accomodate that. So the option always exists to bond the enclosures, remove the bonding jumper and isolate the grounded circuit conductor. regardless of the need for a grounded neutral at the second building it is still necessary to install it if the service is grounded. If the second building is not going to have any loads connected to the neutral then it may in fact be an expensive useless wire but in this jurisdiction it can be reduced but no smaller than the required ground. Then if neccessary it can be grounded.

Neutral not required as bond conductor will provide a path back to XO during a ground fault.

I think if you read Mikesh's posts and then go to the CEC and read the pertinent code rule very very carefully, you will see that the CEC requires a neutral in this situation. Regardless of personal opinion it is what the CEC requires.

10-204(2) deals specifically with services. A consumer's service is defined as from the service box to the point the supply authority makes connection. Is there another definition?

10-204(1)(d) is specific about no connection of neutral to ground after the service disconnect, the only exception being 10-208.

10-208 gives two options for grounding connections at a second building:

option (a), which I object to in the case of a ground fault protected system, is to ground the neutral;

OR

option (b), which excludes barns, a bonding conductor run with the branch circuit conductors.

In order to require that the neutral be bonded, we must first take a big black felt pen to 10-208(b).

Therefore:
1) No neutral required, unless it is going to be used; or,
2) no ground if the neutral is going to be grounded. That would be a violation of 12-108 at various points.