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Posted By Topic: PowerPoint off a range.

tech2
Apr 03 2014 17:45

Probably not best practice but can a power point be wired off a range circuit? It is for a TV that will be on the wall next to the range switch. The range circuit is 30a and in 6mm2. Or would it be better to put a pi permanent connection unit in.
Thanks.
   

AlecK
Apr 03 2014 18:04

as long as you don\'t use a smaller cable to extend / branch of the circuit, either socket or PCU will be fine.

If your added cable has a lesser CCC than the protection of the circuit, you\'ll have to deal with protecting the smaller cable.

There used to be a rule that protection of socket circuits could only be max 2x rating of socket (ie 20 a for 10 A socket). But that rule has gone.
   

Saturn
Apr 03 2014 18:22

Aleck - with all the advances in medical and science is there any possibility of bottling all your knowledge in the event that something untoward should happen to you? obviously hoping it doesn\'t, but just in case.
   

beewild1
Apr 03 2014 19:11

Aleck

Another F--K up by the rule makers.

This is bad practice and always will be no matter what anyone says!!!
   

Wairewa
Apr 03 2014 19:32

Personally can\'t see an issue with running a fixed load from a PCU on a smaller conductor as being unsafe. Why would a fixed load ever draw more than its rated power? It will always have short circuit protection. Don\'t like to practice either, but there are rare exceptions where it is the only choice, but also it is not illegal. The flex of an appliance, like the TV is probably only 0.5mm protected (I use that term loosely) by a 20A MCB or worse, a rewireable fuse.
   

Russ1
Apr 03 2014 19:36

Provided you permanently connect it and have short circuit protection then it could be compliant with smaller cable size.
   

BrianW
Apr 03 2014 21:41

No different than extending any other circuit. As long as the circuit protection is applicable to the cable size then there\'s nothing wrong with it. So, if your range circuit is wired in 6mm, and your extension is 6mm, then no problem. Dont forget, your circuit protection is for the cable, not whats on the end of it, so as Aleck has already said, if your extension is in 2.5 then your circuit protection must be downsized accordingly. Not practical for a range circuit, so keep the cable size the same, and it doesnt matter what you\'ve put on the end of it. That said, dont forget about the RCD rules.
   

daniel2
Apr 03 2014 21:46

What about RCD protection?

You may have to install a PDL 691RCD or equivalent.
   

Wairewa
Apr 03 2014 21:48

Not if it\'s on a PCU.
   

agoodson
Apr 03 2014 22:36

i have always worked by to fuse a circuit at no more than 2x the smallest rated socket on the circuit. eg 10a sockets fused at max 20a. (and yes i know it is all about protecting the conductor, somebody will say you can have a 10a socket fused at 63a off a 16mm if you want) but there is best practice to consider.
   

BrianW
Apr 04 2014 06:58

Best Practice is to protect the cable, not whats on the end of it. That\'s why we have protection factors for cables in different applications.
   

killy
Apr 04 2014 07:11

A bit of 6mm, a 32 a HPM socket.
No rcd required,the home owner can use the socket for other uses.(even another range)
   

AlecK
Apr 04 2014 08:50

I said i cable size is reduced, the issue of overcurrent protection needs o be address. I didn\'t say that necessarily involved de-rating the 30A protection, but Waiwera has covered that by pointing out that with a PCU overload protection can be by the nature of the load.


There are 2 other issues

first RCD

Killy\'s right that a range socket doesn\'t need an RCD, but there are a couple of condition to that exception:
1 it has to be not readily accessible for general purposes, and
2 it has to be labelled as non-RCD and for cooking only.
The obvious thing to do is use an SRCD so you protect the new socket but leave the range as is.

The other matter is EFLI . If the existing 30A protection is an mcb, just a matter of meeting Table 8.1.
If it\'s a SERF, it has to be upgraded because SERFs \"shall not be used\" for fault protection (of the new bit of the circuit)

--------------

I don\'t regard the fact that this idea is within the rules, though not best practice, as any sort of \"F--K up\".
Quite the opposite.
The rules are not about \"best practice\", they are about \"minimum acceptable practice\".

They set a bottom line that shall not be crossed, and we are free to work to higher, but not lower standards.

Fact is, while it may not be our preferred method of adding a point, if we comply with all applicable rules it will not be in any way unsafe.

   

beewild1
Apr 04 2014 09:16

Aleck

You say in your last post that it will not in any way be unsafe.

I believe that you are utterly totally and completely incorrect. Any sparky that worked for me and did that would be sacked.
   

AlecK
Apr 04 2014 09:19

On what grounds (other than not following your instruction)?

More importantly ( since I don\'t want to get into an argument about unjustified dismissal)

What is it that you think is unsafe?
   

Wairewa
Apr 04 2014 11:14

Sorry everyone, except AlexK, I have to agree, there is nothing wrong with connecting a smaller cable to a larger MCB if the load is a fixed load connected by a PCU. This is how you can run a 1mm2C+E lighting circuit from an adjacent power circuit - which I am sure many of you have done at some time in that old shed down the back of the section. The batten holder is rated at 150W, so it is never going to draw more than 150W - (even if someone were to insert a 275W lamp, it\'s not overrating the cable just the fitting). It\'s well within the rating of the 1mm. In what situation would or could it draw 30A on a 20A MCB with rating factor calculated in? Never. It has close protection for short circuit and fault conditions. No problem. So yes I agree that you can run a rangehood circuit in a smaller cable size (helps with ease of termination) but ONLY if connected by a PCU. The socket solution would need to be run in the same cable size as governed by the circuit protection, as the load will be variable, so becomes an unknown quantity.

As I mentioned with the TV and a 0.5mm flex, we don\'t have fused plugtops as they do in the UK, but a 20A MCB is the only protection upstream of most of the plug in appliances around your home, yet again, that 20A MCB or fuse is not there for the protection of your TV, just the wiring. If the wiring can never draw more than it is rated for then it will never be an issue.
   

Wairewa
Apr 04 2014 11:30

Oh yes, another great use for this is running a vanity light off an adjacent socket. I will confess to having actually done this in my own home as I have rake ceilings. Just pop in a socket with an extra switch for the vanity light and job done. And yes, it is a 1mm2 2C+E run off a 2.5mm circuit protected by a 16A MCB with 63A RCCB containing no more than 3 sub circuits.
   

beewild1
Apr 04 2014 12:55

Wairewa
I think you will see above that you need to down rate your MCB to the size of the smallest cable. In the case of 1mm you need a 10a MCB. Alternatively you must run the same size cable to your light as the plug circuit is wired in and protected to, usually 2.5mm.
   

Wairewa
Apr 04 2014 13:18

AS/NZS3000:2007 Clause 2.5.3.4(b)(ii) plus Figures 2.5 and 2.6
   

Wairewa
Apr 04 2014 13:21

If we are going to be really really pedantic, a 10A MCB on a 1mm2 2C+E TPS is also a rule of thumb assumption. 6A MCB with volt drop over circuit length and totally enclosed and insulated.
   

dbuckley
Apr 04 2014 13:28

2.5.3.4(b)(ii) for 1mm running a lamp, fine.

Don\'t think that 6mm from a range point @ 32A to a double GPO is a sane solution, even if legal. A householder could quite load said double GPO to 30A and the MCB and wiring would hold, but the GPO might not.
   

Wairewa
Apr 04 2014 13:34

Only talking about fixed loads and PCU\'s NOT GPO\'s
   

dbuckley
Apr 04 2014 13:43

PCU, no problemo.
   

BrianW
Apr 04 2014 15:20

While, Yes, the potential for a user to plonk a 30 amp load on the 10amp socket exists, however unlikely, the same potential exists for an end user to connect something else other that the original \'fixed load\' on a PCU. Seems to me to be somewhat more stupid to allow a downsize of cable on a 32 amp circuit than it is to continue the 6mm to a new plug socket. Honestly, what likely hood is there for someone to plug a 30 amp load in? About the same as someone increasing the load on the PCU.

And the court case for unjustified dismissal would be an interesting one.
   

daniel2
Apr 06 2014 07:57

I think the simpler option would be to run a loop feed from a nearby socket outlet and replace that outlet with a RCD outlet, or a unit at the switchboard.

I think, in the future, if any sparky were to do any work in the house and discover a socket outlet or PCU looped off a stove then they would be asking questions.

Keep it simple.
   

Linz1
Apr 06 2014 09:33

Interesting reading some of the \"opinions\" here, and my comment would be why not. I have had no need to do such a thing and am not sure that I like the idea entirely but if the rules say you can why not. After all you can hook a light to a plug circuit as long as you use the same size cable, and if a fixed load through a PC the flex may well be smaller, like the .5 or .75 flex on a light pendant connected to said light.
   

justsuppose
Apr 06 2014 15:43

socket taken off a 32A cooker circuit also reducing a cable size without reducing the circuit protection accordingly... may not strictly be wrong according to the finer print of the regs which as usual the NZ texas lawyer sparks will try and justify what I consider a wrong.. far too many openended get out clauses in the regs....

what this country is short of is a suitable piece of equiptment in the product range to enable a local fuse to be put into the circuit, UK uses a fused spur unit, basically a accessory plate with a fast acting cartridge fuse built in.. installed when you may have a local socket wired in 2.5 in a kitchen and you want to take a 1mm cable off to some undershelf lights, just fit the switched version called a switched fused spur and fit a 3A fuse.. problem solved 1mm cable now correctly fused at 3A...
   

Brado
Jun 29 2019 23:06

Hey guys

I have a question that relates to this situation. I’m needing to run a PowerPoint for a rangehood and was wondering, if I looped off the 32a 6mm range circuit, what configuration would I need to do. Run a 6mm cable up to a PowerPoint for the rangehood would the rangehood PowerPoint need to be 32a and would I need to rcd protect it?
   

Pauly
Jun 29 2019 23:43

dbuckley It would be the same if you were to install a double GPO supplied by a 2.5mm tps cable, controlled by a 20 MCB. Then homeowner plugged in a 4 way box to one side of the GPO (max rating 10amps) then plunged in multiple appliances that could exceed 10amps.
   

mowgli
Jun 30 2019 13:02

Beewild1, with respect, I recommend you open the current rules and read them cover to cover. I'm guessing a lot has changed since you started out.

While nothing you've suggested is unsafe, it absolutely exceeds the requirements of the rules in force today. That's a great way to run a business but a lousy way to win an argument.
   

SymonS
Jun 30 2019 18:46

@ Pauly.

Thats exactly why the mcb rating shouldnt exceed the ccc of the smallest cable in the circuit. It matters not what, or how many 10a sockets are on the end of the cable if the mcb is correctly matched to the cable, and for that reason I don't accept that looping off a range circuit with a smaller cable without reducing the size of the breaker is acceptable practice.
   

Pauly
Jun 30 2019 19:43

SymonS

Yes I do understand that. Actually read the post I’m referring to.
   

mowgli
Jun 30 2019 20:28

SymonS have a read of 2.5.3.4 Omission of overload protective device.

Looping off the 6mm with a smaller cable without overload protection is allowed, subject to conditions. No socket outlets is one of those conditions.

A fixed load (eg PCU) that is incapable of causing an overload (eg rangehood) is allowed provided all other conditions are met.
   

SymonS
Jun 30 2019 21:03

Just because it's 'allowed', doesnt mean it's acceptable! A PCU now could just as easily turn into a socket, purchased from Bunnings by a builder, at some point in the future, and at that point it becomes unsafe!

I'm with Beewild on this one. Not on my watch!!
   

Pauly
Jun 30 2019 21:57

SymonS

Ok so I better go back and replace all the circuit protection that I have installed on power circuits to 10amps max so I protect the pins in the GPOs.
   

mowgli
Jun 30 2019 22:43

SymonS how do you sleep at night? If I had to guard against all the illegal things that builders and homeowners might do after I've left... well, I wouldn't leave.
   

AlecK
Jul 01 2019 08:20

"Just because it's 'allowed', doesnt mean it's acceptable! "

Actually that's exactly what it does mean. The wiring rules set the minimum acceptable practice. We are not required to anticipate that others may later carry out unlawful and / or non-compliant work.

That said, I'm not a big fan of using a PCU to avoid having to fit RCD protection, nor to avoid installing overcurrent protection for reduction of CCC.

   

Wairewa
Jul 17 2019 21:44

Oh my goodness... 5yrs on and my head still hurts! Just leave the plug on the rangehood flex, and plug it into the side of the range like we've always done. Even if someone's wired the internal SERF with a roofing nail, at least the pole fuse will provide short circuit protection. It's still never going to create an overload situation.
   

pluto
Jul 18 2019 09:27

I would suggest that you all read what is actually provided for in AS/NZS 3000:2007.

Then key point many have missed "You can not use a socket outlet with this concession if is only applicable for fixed wired direct connections only, e.g. ceiling rose and PCU, so that the maximum loading is fixed and can NOT be exceeded.

BTW the ONE second curent rating for 2.5 mm2 TPS is 278 amps and 1.00 mm2 TPS is 111 amps, if the EFLI is correct, the 0.4 second protective device operation time will protect the looped off smaller cable.
   

COYS1
Jul 21 2019 20:50

"BTW the ONE second curent rating for 2.5 mm2 TPS is 278 amps and 1.00 mm2 TPS is 111 amps, if the EFLI is correct, the 0.4 second protective device operation time will protect the looped off smaller cable."

Hi Pluto, do you have a reference for these figures?

Thanks
   

pluto
Jul 21 2019 22:09

Nexans NZ general technical information in the Nexana NZ cable book
   

Wairewa
Jul 25 2019 21:37

Thank you Pluto, concise and to the point. It still shocks me how many people don't seem to be able to grasp coarse and close protection methods WRT fixed loads. Maybe this post will get dredged up with some new fresh rules in another 5yrs!
   

AlecK
Jul 26 2019 09:21

We haven't used "coarse protection" rules for nearly 30 years.
And this thread has nothing to do with coarse vs close - both of which relate only to overload protection, being a comparison of how long before the protection operates (i.e more or less than 4 h at 150% rating).

This is about not providing any overload protection at all, on grounds that an overload is not possible due to the nature of the circuit configuration and the connected loads providing both short circuit.
Perfectly logical: why provide protection against something that can't happen?

Whereas in the long-ago OP; it was about a socket, where an overload could happen so o/l protection must be provided.

Pluto's latest post isn't about o/l protection at all; it's about short circuit protection. So it's just muddying the water further.

Both s/c & o/l protection share the same default rule (2.5.1.2: at origin and at each reduction in CCC); but each has a different set of Exceptions.

However I suspect you're right that it will keep coming up in future; due to widespread failure to actually read the damn book (let alone spend any time thinking). But I doubt these rules will have changed at all.

After all, the last substantial change was 1993, when the "only one way to do it" system of 1976 Regs was dropped in favour of treating electricians as intelligent people capable of working things out and accepting responsibility. And there hasn't been even a tweak to them since 2000.

   

Wairewa
Jul 30 2019 09:05

Yes AlecK,
Coarse protection is alive and kicking, given that one has to work with it and within it's capabilities, it would remiss of any training institution to not discuss these IMO. The Temuka rewireable fuse will (hopefully!) protect any short circuit in an installation, but will do nothing to assist overloads in a safe practical time.
Just thought using the term close and coarse still have relevance when erring on the side of caution.
These terms are still in the polytechnic training manual to the best of my knowledge, well they were 6yrs ago.
   

AlecK
Jul 30 2019 09:50

True there are lots of installations / part installations that were installed under old rules, and for which these terms are relevant.
In that context, agree trainees should be aware of the concept. Eg, if they find a circuit with more than 2 sockets that's protected by a SERF (coarse protection); then it's no longer compliant with original rules and is therefore not allowed to remain in service. Whereas the "close protection" of an mcb allowed more than 2 sockets.
The only other relevance would be that the old CCC ratings for conductors varied according to coarse vs close.

However they were ever only ever relevant to overload protection; and they have zero relevance for any new installation work including this scenario of supplying a range hood from the range subcircuit).

If existing protection for the range circuit is a SERF; then it simply must be upgraded before ANY extension of or branching from the circuit is permitted.
That's nothing to do with coarse vs close o/l protection; it's simply that SERFS are not permitted as either o/l or s/c protection for conductors being installed.

As for a SERF's capability for providing short circuit protection; it's very limited. Generally the PSSC on a house is close to the 1 kA rating of a brand new SERF; and once there's significant deposits of carbon or copper, it can't be relied on to clear any fault.