ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades Pardon?

lyle,
We don't actually use a Protective device at the switchboard panel end of the Service Line here.
So really, the Service fuse has to co-ordinate with any of the Sub-circuit fuses.
At the end of the day Lyle, the Service fuse is just a last-resort fuse, it just protects the Service line itself and the metering equipment.
When Electricity was first reticulated here in NZ, a Main Fuse-switch was used, but as installations were upgraded, it was thought un-necessary and the idea done away with.

Lyle,

The service fuse here is similar to what you'd find in Northern Ireland or elsewhere in the UK (although the physical design of the fuse may, in some installations be quite different)

Typically it's either 63, 80 or 100Amps

Regardless of the type of fuse, it's installed and sealed by the ESB (poco)

In recent years the ESB has started installing isolators after their meter, in some cases actually built into the meter itself. This is the demarkation point between the network and the consumer's equipment.

The consumer unit still carries a main switch and main fuse (or breaker in recent years). This would usually be the same rating as the service fuse.

The logic is to protect the consumer unit and wiring against fire should it become accidently overloaded... e.g. if a consumer somehow manages to connect >80Amps of equipment across several final circuits.

The tripping / blowing characteristics of the main fuse / breaker would be similar to any normal diazed fuse or MCB ... so, it would tend to blow more rapidly than a service fuse.

If you have more than one panel / consumer unit. Each one would have an appropriately rated main fuse. E.g in apartment blocks, garage services etc etc..

It's probabally not 100% necessary in a standard domestic installation, but it has remained the normal practice here and is required by the wiring rules.

[This message has been edited by djk (edited 02-19-2005).]

In Auckland most domestic houses are protected by 63 Amps HRC fuses in pillars via underground supplies, or 63A rewirable Crown lynn fuses via overhead supply.
In the Waitemata Electric Power Board days pre 1991, if you had a 6 kW Spa heater a 63 Amps MCB was fitted in series with the main switch and meter to avoid blowing especially the rewirable pole fuse, and could easily be reset by the home owner if they had the spa and electric range on at the same time, and other heating in winter.
A 63 Amps HRC in the pillar would usually go before the braker tripped but was easily replaced by the faultman. After the deregulation in 1992 the old 03 tariff disappeared for controlled fixed wired heating appliances and so did new installation of these MCB's.
Regards Raymond

Raymond,
Welcome to ECN, mate!.
Yeah I agree with your comments on the pillar box fusing tripping before any of the installation fusing.
It's good to see MCB protection in houses these days, especially considering that the bulk of our Mains fusing is now HRC.
As a Faultsman, being called out because somebody blew thier pole fuse through over- current and the house fusing never tripped, is a tad worrying and annoying too.

Hi Trumpy,
Thanks for your welcome.

Yes MCB's are certainly the way to go and with ELCB's as well makes the installations a lot safer and the protection a lot closer.

I have struck a few imes at fault work that when a 30 Amp rewirable range fuse blew, when an element shorted out, a hole was blown in the element and it took out an aged 63 Amps polefuse.

A lot of the newer ranges have only 15 Amps protection on the outlets and rely for the elements solely on the 30 Amp MCB or rewirable

Ray,
Mate, the majority of the newer ranges I've seen here, use one single FUSE in them, although they have terminals for 2 phases + Neutral.
You might have a better idea, it has been 3 years since I installed a free-standing Range.
It is entirely up to the Installing Electrician.
You sign the Certificate of Compliance, it's on your head.
Some Electricians here, don't seem to be able to comprehend that little fact.
Sad really.

Just refreshed my mind after a fault job.

Some panels had the red warning label on them.

The short circuit current exceeds 5000 Amps in this installation.

Am I right in believing the electricity entities consider the pole fuse as only a short circuit protection device, NOT an overload protection device. In other words our current installation methods don't include any overload protection device on the consumer mains, such as a main breaker on the switchboard rated to protect the mains. I think there is a proposed change to the next edition of AS/NZS3000 requiring overload protection on consumer mains.(it's too late tonight to check)

Briselec,
HRC fuses are used for both Short-Circuit and Overload protection.
The rewirable pole fuses here can really only be counted on to provide Short-Circuit protection, thier performance as an Overload protection.
It's just a good thing that we have been rather lucky that the rewireable fuse elements in the house have de-energised the faulty circuit.
I hate tinned copper wire fusing, although it has been outlawed here, you know the story....
Briselec,
One comment I would like to make with regard to the protection of Consumers Mains, is the fact that no protection can protect upstream from itself.

That's true for short circuit protection but for protecting against someone installing more load than the cable is rated for, it doesn't matter where the device is as long as it's before the load.