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Posted By Topic: Gas isolators etc - We\'ve been doing it all wrong

DougP
Jul 02 2018 13:33

ESR\'s Schedule 2 AS/NZS3000 modifications -

AS/NZS 3000
AS/NZS 3000:2007: Electrical installations (known as the Australian/New Zealand Wiring Rules): including Amendments 1 and 2, subject to the following modifications:
1. In 4.5.2.3.2, change “warning sign shall be installed” to “warning sign shall be installed or fitted in domestic installations but may be omitted from all other installations”.
2. In 4.18.1(b) and (c), change “all live (active and neutral) conductors” to “all active conductors”.
3. Add a new paragraph to 4.18.2: “In New Zealand, only electrical equipment that is directly associated with the gas supply may be installed in the hazardous areas of a domestic installation, shown in figure 4.10.”
4. Replace 4.18.3 with “In New Zealand, only electrical equipment (including metering equipment) that is directly associated with the gas supply may be installed in the exclusion zones of a domestic installation in figure 4.11.”
   

DougP
Jul 02 2018 18:21

I see that 4:18 has been updated in 3000:2018

And that the switch controlling an inaccessible socket outlet only needs to be a switch, not an isolator. << At least that\'s the way I read it - 4.18.1.3(b)
   

mowgli
Jul 02 2018 20:50

That first bit isn\'t new. It\'s been in ESRs since I don\'t know when. I cut those modifications out and stuck them in the margins next to the changed clauses.
   

mowgli
Jul 02 2018 21:00

Need to read 4.18.1 in conjunction with 2.3.2.2 so it\'s not talking about just any switch.
   

DougP
Jul 02 2018 21:12

Searching back, I see that there has been some discussions about this last year which I must have missed.

The only discussions I thought I remembered were discussing the difficulty getting double pole switches.

But in 3000:2018 the part about the switch still doesn\'t seem to be worded right. It calls for a means of isolation, which in 4.18.1.3 (a) and (b) is called a switch and is in combination with a socket outlet (which could be the actual isolation), whereas in (c) it is specifically called an isolating switch.

If they can put the word \"isolating\" in (c), surely they would have put it in (b) if it was required?
   

mowgli
Jul 02 2018 21:37

Ahhh sorry I was looking at 2007.

I guess the question is whether a \"means of isolation\" must comply with the requirements of a \"device for isolation\"

It certainly reads as though the writers were trying to make a distinction between a/b and c
   

mowgli
Jul 02 2018 22:44

DougP the big change is that in 2007 the means of isolation had to be accessible. So the inaccessible plug in b didn\'t count and the switch had to be the means of isolation.

In 2018 the accessibility requirement is gone. So if the inaccessible plug socket is \"available\" by, for example, moving the gas appliance then it can be the means of isolation. The switch becomes a functional switch only.

Where there is no plug socket then the switch must be an isolating switch.

The key may be in the part 1 definitions of \"accessible\" and \"available\"
   

AlecK
Jul 03 2018 16:45

WRT gas appliances
the same three options are there, just that if your means of isolation is a switch as against a socket then the switch has to be an isolation switch. Not a change as such, just making it clear for those who couldn\'t work it out.
The original wording came from the gas installations standard. The aim is to get to the stage where there are no conflicts between different standards.
   

mowgli
Jul 03 2018 18:11

I think the new wording is much clearer. A thumbs up for the standards team.
   

mrsparky
Jul 04 2018 07:45

I may be way out here as I havnt been fully following the gas appliance discussions but would a 2pole mcb on the gas appliance circuit satisfy the requirements?
   

pluto
Jul 04 2018 09:15

mrsparky Jul 04 2018 07:45
Your comment
I may be way out here as I havnt been fully following the gas appliance discussions but would a 2pole mcb on the gas appliance circuit satisfy the requirements?

My comment
It would exceed the current NZ mandated requirements, as such this is acceptable.

But if switchboard room for mounting of the MCB is limited, the use of the NZ permitted single pole MCB may leave room for another extension for another final subcircuit and the need for RCD protection without the need to replace the whole switchboard.
   

StevenR
Jul 04 2018 10:47

You could use a single width 2 pole RCBO on the gas heater circuit and take uo no more space than normal in the switchboard.
   

pluto
Jul 04 2018 11:51

StevenR Jul 04 2018 10:47
Your comment
You could use a single width 2 pole RCBO on the gas heater circuit and take uo no more space than normal in the switchboard.

My comment
a single width RCD neutral pole does NOT have an decent impulse voltage rating to be considered an ISOLATING switch.

A souble width device will have an impulse voltage rating for BOTH poles
   

mowgli
Jul 04 2018 13:05

It doesn\'t matter what you have at the switch board. The regs require a means of isolation that is adjacent to the gas appliance.
   

TheDon
Jul 04 2018 13:44

Mowgli\'s comment is correct so to correctly answer MrSparky\'s question, No a two pole MCB at the board would NOT satisfy the rules.
A point to not though is that you don\'t need a two pole switch or isolator anyway if it is a single phase appliance, NZ only requires switching of the active conductors not \"Live conductors\" like they have to do in Aussie
   

richard
Jul 04 2018 22:07

In the past I have used a recessed entertainment box somewhere unobtrusive with an isolator or socket inside, cover back on with label on outside, customer happy.

   

codaxx
Nov 06 2018 11:17

Are there any normal size isolates on the market that a close to resembling a standard hob switch?
Isolated definition:
-on/off clearly identified
-be able to be locked in the open position.

I am installing one now and will just put a normal HOB switch above bench and under the bench, in cupboard next to gas hob, will install a 10a single socket and a plug and lead on the hob itself (only needed for piezo switch).
   

AlecK
Nov 06 2018 13:18

There\'s more to isolation than just those two things; see 2.32.2 devices for isolation.
The impulse voltage withstand function is crucial, and difficult - maybe impossible - to comply using micro-gap switches.
   

Someone
Nov 07 2018 16:10

Could feasibly put a socket in the next cabinet over from the hob, similar to what typically happens with dishwashers. Being able to unplug it meets all the isolation requirements.