cooker switch for 12kw cooker

[tigerpaul]

Right then, I'm putting a new circuit in for a 12kW cooker

12000W / 230V = 52.17 amps

That would be the full load current, and I need a cooker switch that is capable of switching the full load current right? (BS 7671 regulation 537.3.2.5)

So as most cooker switches I have found are rated only at 45A that leaves me a problem, what kind of switch can I use?

Any ideas fellas??

 

[ashdog]

Hi Tigerpaul

Once you apply diversity to you figure (52.17 amps) you will come in well under the 45 amps of cooker switch

Diversity for cookers is 10a +30% of remaining current

 

[tigerpaul]

Now at college, we were taught you apply diversity to all your maximum demands of individual circuits so you can calculate the total assumed current demand of the submain.

This was because it is unlikely that all the lights, all the sockets, the shower, the cooker, everything would ALL be on at the same time.

Quote from The Electricians Guide to the 17th Edition by John Whitfield:
"At Christmas it is likely that 2 ovens all 4 hotplates and a 3kw ketle could be simultaneousely connected. Just imagine the chaos that a disconnected cooker circuit would cause! This alone is a very good reason for being generous with cable and protective ratings"

The cooker I am feeding has 6 hotplates, and I dont know why anyone would install one unless they did need to use many hotplates at the same time (big family/did a lot of entertaining etc)

This brings me back to my original question, where do I find the cooker control switch that can break 52.17A ?

 

[zupos40]

Yes rating you state is if you were to theroetically put all the hot plated on full, turn the oven upto max setting etc, it would still not be drawing 53 A, generally the 30% diversity was arrived at after testing, the assumption is that if all the hot plates were switched as they are thermostatically controlled 1 would be taking full power, 1 would by switching on, 1 would be switching off, 1 would be taking no power as it reached temperature etc etc, as a safety factor they added the 10 A to the equation. Same apply to the oven once it reaches temperature the power is switced off/ reduced.

It easier to see the principle on an gas oven, switch it on set it to say 200 C leave it on for say 20 mins, then open the door and look at the flame. high or low.

I beleive your article is on about cable sizing 10 mm or 16mm depending on installation conditoion lenght of run etc and install max size control unit

 

[Darkwood]

What kind of premises is this cooker going into, ive noted with commercial and industrial kitchens they often use an appropriate isolator with a 60amp or 63amp been a common size.

 

[tigerpaul]

Its going into a big house. They want this big six ring ceramic range.. So its not your average cooker.
I reckon on ten mil cable fifty amp mcb. But then the switch is only rated at forty five amps, which concerns me a bit.

 

[Spudnik]

Off topic a tad but i have just installed a new double oven at a clients property.

I turned the main oven on (full) and clamped the line conductor.

It was only drawing around 8 amps from cold, including the fan.

 

[sparks1234]

sounds like a brittannia oven to me , some of theirs are 80 amps

 

[steamboatwilly]

RangeMaster supply domestic cookers at up to 15Kw. In the RangeMaster iinstallation material it specifies a 45A switch (allowing for diversity). The Regs generally allow an installation to be guided by the supplier's recommendation (assuming it's an, er, reputable supplier).

You should be fine with a 45A switch. The cable size will depend on other circumstances such as length and routing.

 

[Spudnik]

Bring on the 16 T&E!!!!

 

[tigerpaul]

It's gonna be 10mm2 T+E, 50a mcb and 45A cooker switch. Its run on its own, no insulation.. Should be fine. My only worry is if the switch can handle it when it's on full load.
Zupos reckons the elements will be cutting in and out as the cooker reaches and then maintains temperature, so hopefully it shall be fine...