Dear all,

I'm pulling a new wire from DB for my induction cooker. Not decided which hob model, but should be 3.5-5 kW type.

1) may i know if 4mm wire is sufficient?

2) When someone says 4mm, he means 4mm² cross sectional of copper part or 4mm diameter?

3) what rating mcb should I use, 20 or 32A?

4) can I tap from this new cable to power the kitchen hood and a new SSO?

5) should I go for 6mm cable to future-proof? Maybe future hobs are more power hungry or I can further tap off power from this line to install built-in oven? Is installing 6mm vs 4mm cable much more difficult and costly?

6)EDIT: electrical contractor suggests pulling 2 sets of 2.5mm² wires to give load of 30A. Is this type of "parallel" cabling common?
Thank you.

This post has been edited by mushigen: Mar 15 2023, 11:31 AM

6mm is futureproofed especially since u don't need to hack up the walls again to change it later in the future.

32A is mostly for high-powered instant water heaters such as the Stibel Eltron DHC 8 XG.

20A is sufficient for hob.

1. 4mm2 is sufficient. provided its copper and real sirim approved. eg mega cable.
2. refer to cross section area of the wire.
3. c25 for 4mm2, c32 for 6mm2
4. yes can for small load
5. you may want to use 6mm2 sekaligus for future proofing.
for oven prefer to have dedicated cable. cannot run both at same time.

note: do not use socket for the stove. use a dedicated oven switch.

How about running 2 sets of 2.5mm² wires as suggested by contractor? Contractor says this combo can give 30A and also 6mm² cables are more difficult/expensive to source.

Basically the 4mm² copper wire can carry around 30A. The TNB guideline is the 20A MCB with 4mm² wire will support 2 x 13A socket.

Yes. 2 x 2.5mm² is recommended by TNB for 2 x 13A sockets too with 20A MCB

consider 2x 4mm2 better.

It's very common

6mm is pretty common when purchase from a electrical wiring supplier. General hardware usually don't sell these.

I think this is definitely more than what my small kitchen requires.
My concern with running 2x cables is what if there's a discontinuity or uneven load carrying capability in one of the cables - loose connection, cable fault/breakage, etc? Before the MCB trips, the wire that supports more load may overheat.

That's what I think too. But costs almost double that of 4mm² . Rather having just one set of wires (either 4mm or 6mm) than the messy 2x2.5mm² system (6 wires to pull).
Internet research gives varying load of 4mm² wires, on paper it's sufficient for the present needs. So I wonder if it's too kiasu to go for 6mm².

2 set of 2.5mm.sq is common. Mostly done to reduce cost as 4mm.sq cable are very expensive (and you need to buy at least 2 color for the live and neutral, earth can use 2.5mm.sq green).

6mm.sq overkill for 5kW load. No need for that.

Understand that 6mm² is overkill. Cable quality aside, what's the usual guideline on the max current 4mm² wires can take?
Also, do we use 220, 230 or 240V in calculation of current vs wattage?

Is 2x2.5mm² laying cost (material plus labour) cheaper than 4mm²? With 4mm², only need to pull 3 wires vs 6 for 2.5mm² per my conversation with the contractor.

Are you referring to Energy Commission's guidelines because I haven't come across any guidelines from TNB for residential wiring.
For 20A, a 2.5mm² wire is sufficient.

3.5kW and 5kW require different sources, if you are really unsure i would recommend you plan for the maximum requirements which would be 5kW.

1. For 5kW you would need to use 6mm² or larger cables.

2. They are referring to conductor CSA which will be printed on the wire sheath.

3. 5kW will be 32A.

4. It is not recommended to do so because of difficulty in looping such a large wire. A loose connection is a hazard for fire. Looping for 13A SSO are generally fine because 2.5mm² are easy enough to loop at the 13A SSO receptacles.

5. 6mm² is required for 5kW hobs. An oven will need its own wire and MCB because these are high power appliances which are not recommended to share circuits.

6. This type of installations are possible if the workmanship is proper, the wire termination must be done properly so there are no loose connections. Both sets of wiring should use the same path and wire support system as well to minimize chances of damage to 1 set of wires.

Guidelines are based on MS IEC 60364 Standard. But understanding the standards will be very difficult for laymen to understand as it covers alot of electrical jargon inside.
For calculations, you need to base on the voltage in your premises. Older TNB installations are 240V while all newer installations are 230V.
However, any calculations and sizing of wires are very technical in nature and is best to be advised by a qualified professional. I would advise against any design for electrical systems if you are not trained to do so.

For costing purposes, only your appointed contractor is able to give you a definite answer as pricing can vary wildly from contractor to contractor.

Cable laying labour cost should be the same, we can fit 6x2.5mm.sq in a 3/4 inch conduit (Or use 1 inch, cost difference is negligible). We pull them in one go, not each separately. Use only quality cable by the way. (Something like Mega Kabel brand)

For calculation, you should use 230V.

4mm.sq according to Mega Kable spec sheet are rated to carry 32amp of current (~7.6kW).

edit: 4mm.sq circuit will cost more than 2.5mm.sq (labour+cost). Do note that your usual 13A plug socket are actually ring topology (6x 2.5mm.sq).

This post has been edited by marvinben: Mar 15 2023, 02:27 PM

http://megakabel.com.my/A-1.pdf

you can use this as guideline

4mm2 ->32A

precisely why i recommend go straight to 4mm2 or even 6mm2 instead of 2.5 x 2


if there is loose connection/breakage, the MCB will not trip and may cause fire.
the same reason why ring network is not preferred.

most electrical shop allow to buy in loose cuts, so measure cun cun before cut.

The chart is more on theory than real world application. The calculation will be de-rated to ensure safety margin since wiring direct on wall, in trunk or over the air will give different rating. I think the Europe standard is referring to temp at 40C.

Yes it's not advisable to follow the table without understanding the underlying factors. 32a is not advisable to use 4mm wires.

lazy contractor, last time my contractor pulled 4x6mm, 1 for each socket
and he specifically reminded us not to use extension or 3-way plug for kitchen appliances

so far I using each for oven, microwave, induction hob, and fridge

edit: using 2 separate fuse, my home get 3-phase power
I specifically asked them to make it safe and future proof

This post has been edited by jmas: Mar 15 2023, 06:03 PM

4mm enuf but dedicated