Cable mm2 for Indcution Hob (11kW)?

Forums › Home Workshop DIY › Cable mm2 for Indcution Hob (11kW)?

1 | 2 | 3

MikeAqua

7785 posts

Uber Geek

#2530514 29-Jul-2020 08:46

PolicyGuy:

And then I thought "How much bigger do I want to make my carbon footprint?", and bought an electric stove with an induction cooktop.

I think it depends whether your primary motivation is cooking performance or environmental performance. Induction still cycles. Gas doesn't - the heat is constant.

Currently I have gas hob and a portable induction ring. I'm now thinking of going with an induction hob and portable gas ring with a plug in point by the hob, for the wok and heavy plate.

Mike

MikeAqua

7785 posts

Uber Geek

#2530673 29-Jul-2020 11:40

andrewNZ:

It's the smallest cable rated for that current at that distance. It's borderline for carrying that current continuously.
If the real length is 25m it's 10mm². However maximum demand calcs might bring it back to 6mm².

Thanks, I'll work off 10mm2. Eyeball some of that and it will give me an idea what's doable in terms of routing cable.

Mike

MikeAqua

7785 posts

Uber Geek

#2530674 29-Jul-2020 11:41

gregmcc:

The problem the OP was having (as it seems to me) is that they have a gas oven that just needs a standard 10A socket to run the electronics and igniters and they want to put in a electric oven, this means a cable upgrade which will be a mission in an existing installation.

Good summary. This is exactly the problem I am considering.

Mike

Scott3

3970 posts

Uber Geek

Lifetime subscriber

#2530688 29-Jul-2020 12:13

MikeAqua:

PolicyGuy:

And then I thought "How much bigger do I want to make my carbon footprint?", and bought an electric stove with an induction cooktop.

I think it depends whether your primary motivation is cooking performance or environmental performance. Induction still cycles. Gas doesn't - the heat is constant.

Currently I have gas hob and a portable induction ring. I'm now thinking of going with an induction hob and portable gas ring with a plug in point by the hob, for the wok and heavy plate.

Given you have a gas connection handy, you could consider a combo cook-top (assuming you have space to go 100mm wider):

https://www.asko.com.au/products/kitchen-appliances/cooktops/gas-induction/hig1995ad

Glass topped except for the wok ring for easy cleaning. There seems to be enough of a market of people who generally prefer induction cooking, but still want a specialized gas work burner for the above product to exist.

There is such a thing as a an induction wok cooktop, but gas still seems to be the preference where available.

Other option is to go the Domino route, allowing you to mix & match.

With regards to performance, Yes induction does cycle at lower power levels, but I have never found it to be an issue. Cookware has quite a lot of thermal mass, so the variation in temperature from sub 5 second cycles is likely to me negligible.

I don't know if there was something wrong with gas cooktop at the last house I had with one, but I always felt it was lacking in heat output - My current induction cook top can get a skillet to smoke point very quickly.

With regards to environmental, arguments can be made both ways. Induction is more efficient (less heat wasted around the side's of the pan), and our power gird is 80% green. Long term this number is expected to trend upwards. On the other hand, around peak cooking times, (currently) gas fired peaker power plants are often running. It is a lot more efficient to use the natural gas directly for heat than to go through all the effort of making power from it, transmitting it, and then turning it back into heat. Compared to space & water heating, the cook top is a relatively small energy use.

Also if one has natural gas connected, the marginal cost of it is less than that of electricity. (can be the opposite story for LPG is one is on a standard user power plan, and inefficiency of gas cook top is considered))

Main selling points for induction is safety, fine level of control, gas like rapid control response, and no need to pay gas connection fees (or deal with bottles). Obviously the latter point is irrelevant for households that have gas for other reasons.

MikeAqua

7785 posts

Uber Geek

#2530699 29-Jul-2020 12:41

Scott3:

Given you have a gas connection handy, you could consider a combo cook-top (assuming you have space to go 100mm wider):

https://www.asko.com.au/products/kitchen-appliances/cooktops/gas-induction/hig1995ad

Glass topped except for the wok ring for easy cleaning. There seems to be enough of a market of people who generally prefer induction cooking, but still want a specialized gas work burner for the above product to exist.

I've put in a 90cm Robinhood range-hood that works really, really well with our 70cm cooktop. The advice I've received is to have the range-hood 100mm wider than the cooktop. With the wok ring at the end, I'm dubious about effective smoke collection from a wok would be. I guess I could do some experiments - get some oil smoking in a wok and see how wide I can go.

The cooktop sits above a draw cavity and a 800mm cut out definitely works, but I'm dubious about the 860mm cut-out required for a 900mm cooktop.

Mike

phrozenpenguin

841 posts

Ultimate Geek

#2530794 29-Jul-2020 14:47

SomeoneSomewhere:

But yeah, you're unlikely to run both sides against the limiter simultaneously for more than a minute or two, especially when you look at what the oven's doing. You're probably fine to put a 7.4kVA unit and a basic oven on the same 32A feed; worst case you trip a breaker.

I was thinking similar after doing some maths. But if that "worst case" i.e. tripping the breaker happens every time you cook a big meal using both the oven and the induction cooktop, it isn't going to be a good outcome!

gregmcc

2147 posts

Uber Geek

ID Verified

Trusted

Lifetime subscriber

#2530871 29-Jul-2020 17:02

MikeAqua:

Wiring has to be adequate for the hob to run at the max theoretical load the device will allow (they have internal control systems)

No sous chef! Just a vaguely competent amateur chef, who holds largish dinner parties. If the weather is rubbish, meaning I can't use the BBQ, and I have crowd to feed I will have the gas hob fully loaded and cranking.

Un...no As/NZS3000 has maximum demand tables, in particular table C1, and there additional table C4, all something a good electrician should take in to account when working out cable sizing.

Sharesies

Trade NZ and US shares and funds with Sharesies (affiliate link).

SomeoneSomewhere

1804 posts

Uber Geek

Lifetime subscriber

#2530907 29-Jul-2020 17:59

Which is specifically in a section marked 'Informative' for good reason; it is not mandatory to be complied with. It would be a problem from a CGA standpoint if you did it without making the customer thoroughly aware that what's being done is unusual (services shall be fit for a specified purpose), but it's not illegal and has its place, particularly in cases where the cable can't be replaced.

2.2.2 allows maximum demand to be determined in a variety of ways, including limitation - this is what allows you to have many 10A sockets on a 16A breaker even if someone can plug in a pair of space heaters.

Even considering that table C4 (C1 is not relevant as we're not considering the mains to the whole house), you'll note that a 32A circuit is considered good for up to 13kW of cooking appliance. 3.5kW of oven, 7.5kW of hob is well inside that at 11kW, and given there are some induction cooktops that are down around the 6-6.5kW range and some ovens are 3kW or less, I would argue that you could sit within that 10kW/25A bracket.

gregmcc

2147 posts

Uber Geek

ID Verified

Trusted

Lifetime subscriber

#2530917 29-Jul-2020 18:28

SomeoneSomewhere:

Which is specifically in a section marked 'Informative' for good reason; it is not mandatory to be complied with. It would be a problem from a CGA standpoint if you did it without making the customer thoroughly aware that what's being done is unusual (services shall be fit for a specified purpose), but it's not illegal and has its place, particularly in cases where the cable can't be replaced.

2.2.2 allows maximum demand to be determined in a variety of ways, including limitation - this is what allows you to have many 10A sockets on a 16A breaker even if someone can plug in a pair of space heaters.

Even considering that table C4 (C1 is not relevant as we're not considering the mains to the whole house), you'll note that a 32A circuit is considered good for up to 13kW of cooking appliance. 3.5kW of oven, 7.5kW of hob is well inside that at 11kW, and given there are some induction cooktops that are down around the 6-6.5kW range and some ovens are 3kW or less, I would argue that you could sit within that 10kW/25A bracket.

I would argue that table C1 should be taken in to account as there is a significant increase in installation load this has the very real potential to push the mains beyond it's capacity. Simply ignoring this calling it not relevant it poor practice and could result in an electrically "Unsafe" installation.

SomeoneSomewhere

1804 posts

Uber Geek

Lifetime subscriber

#2530936 29-Jul-2020 19:15

gregmcc:

SomeoneSomewhere:

Which is specifically in a section marked 'Informative' for good reason; it is not mandatory to be complied with. It would be a problem from a CGA standpoint if you did it without making the customer thoroughly aware that what's being done is unusual (services shall be fit for a specified purpose), but it's not illegal and has its place, particularly in cases where the cable can't be replaced.

2.2.2 allows maximum demand to be determined in a variety of ways, including limitation - this is what allows you to have many 10A sockets on a 16A breaker even if someone can plug in a pair of space heaters.

Even considering that table C4 (C1 is not relevant as we're not considering the mains to the whole house), you'll note that a 32A circuit is considered good for up to 13kW of cooking appliance. 3.5kW of oven, 7.5kW of hob is well inside that at 11kW, and given there are some induction cooktops that are down around the 6-6.5kW range and some ovens are 3kW or less, I would argue that you could sit within that 10kW/25A bracket.

I would argue that table C1 should be taken in to account as there is a significant increase in installation load this has the very real potential to push the mains beyond it's capacity. Simply ignoring this calling it not relevant it poor practice and could result in an electrically "Unsafe" installation.

I was referring to the question of whether the existing cable run to the stove is adequate. The house mains is a separate question, that should still be asked, but a separate question.

Again, though, table C1 is still informative, one of four available methods, and not mandatory to follow and cannot result in an installation becoming unsafe. The bar to consider something 'Electrically unsafe' is quite high - none of the conditions in Reg 20 have any bearing on this that I can see.

1 | 2 | 3