Canadian Electrical Code

[gimmephone]

Hi,

I am designing an electrical panel for my fourth year electrical engineering project and had a afew questions about the electrical code in Canada.

The main disconnect that I have has a single set of contacts, which means that the input AC neutral is not disconnected. Is this a violation of the Safety Code? I am still fusing both the Hot and Neutral with separate fuses. Is it still a violation?

I have hardwired the power on and E-stops with hardwire safety (contactors, relays) and am using software safety as a backup. What level of safety does this correspond to(Level 1,2,3)?

At last, I want to display the sequence of buttons the user has to press to make the machine operational bu using Allen Bradley Indicator Push Buttons by showing flashing lights for the button that has to be pressed. This means that the PLC has to be powered as soon as the Main disconnect has been turned on and the Power On light, which is AC will be flashed as soon as the main disconnect is turned on but the user has not hit the switch to turn the power to drives, servos etc on. Is this a violation of the electical code?

Thanks

 

[randylud]

http://www.csa.ca/Default.asp?language=english

 

[panic mode]

we build custom machines (each is different and we do lots of them) and each is inspected by ESA (Electrical Safety Authority, former Ontario Hydro)

fuse on phase - fine
fuse on neutral - NOT! (you could use multipole circuit breaker if this is what you want to do)
disconnect switch to only kill phase(s) - fine
plc powered as soon as disconnect is on - fine
hardwired e-stop circuit - depends what circuit you use, application demands or if you applied it correctly.

Please note that Ontario Electrical Code and Canadian Electrical Code are not exactly same. (Ontario is more strict on few little things like for residential, don't even remember anymore since we don't do that).

 

[Sliver]

Gimmephone,

You need to know why seperately fusing or switching the neutral is dangerous and violates the code.
Any idea?

Brian.

 

[gimmephone]

As far as I can think, I do not see any harm in adding a fuse to the neutral except for added cost due to redundancy. The fuse on the Hot wire handles all the possible faults - Hot-Ground, Hot-Neutral. Even in the Neutral-Ground fault, current will flow to the ground(Kirchoffs law). Since the neutral is floating, I thought it would be a good idea to add a fuse to the neutral so that even if someone accidentally reverses the phases inside the panel, protection still exists. This panel is for a CNC machine that I built and will be used by students in the subsequent years so such a situation can occur. I just wan't to make sure that it is as safe as possible.....Safety is Job#1!!

I know grounding the neutral is not a good practice as the potentials on the other outlet grounds can be affected so I don't see more solutions. Please let me know if this is a violation and potential solutions.

Thanks

 

[panic mode]

if you are in Canada, I strongly suggest to take CEC course. it is offered just about everywhere...

 

[Herm]

To answer this question we would need to know the AC voltage and how many phases.

If the supply is the 115VAC the you normally do not fuse or disconnect the neutral.

If you are getting the 115VAC from a 220 3 wire source you would fuse and disconnect the neutral.

Herm

 

[gimmephone]

It is a single phase 115VAC source

 

[corkers]

Why not to fuse a neutral

Just a thought guys, if you fuse the neutral and this fuse blows or is removed for some reason a person could make the mistake of assuming the power is off...

In fact under Australian Wiring rules it is prohibited to fuse the neutral conductor (except under very specific circumstances). For those Aussies and Kiwis who don't believe me AS/NZ3000:2000 2.2(g).

 

[PeterW]

I know I know I know the answer


Youll kill someone....

 

[Binaural]

In fact under Australian Wiring rules it is prohibited to fuse the neutral conductor (except under very specific circumstances). For those Aussies and Kiwis who don't believe me AS/NZ3000:2000 2.2(g).

Really, I would have thought it was disallowed under all circumstances. I don't have a copy of that handy, can you recall those special circumstances? Certainly it's not something I could ever imagine designing.

 

[davefinic]

Just a thought guys, if you fuse the neutral and this fuse blows or is removed for some reason a person could make the mistake of assuming the power is off...

Corkers is correct never fuse a neutral if you want to put in a fuse carrier for disconnect purposes then it should be fitted with a solid link but its still best to fit a double pole breaker as this was an old way of doing things often seen in 60's and 70's panels.

Isolating the neutral is also good practice on main disconnect

 

[PeterW]

as this was an old way of doing things often seen in 60's and 70's panels.

You've obviously never worked in canada then.