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Cooker Connection for Single Oven and Gas Hob - Do They Need to be on Seperate Circuit?

Postby Markb2100 » Wed Feb 25, 2015 10:45 am

I have a single oven rated at 2100w and gas hob rated at 600w so neither will draw more than 13 amps individually or combined. Do I still need a separate cooker circuit or can these be connected to a spur from an existing ring and protected with a 13amp fcu? Or run from a new radial circuit in 2.5mm again protected with a 13 amp fcu?
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Postby ericmark » Wed Feb 25, 2015 10:52 pm

In practice yes all can be run off a FCU either spur or radial or direct onto ring.

There is in appendix 15 a statement:- The load current in any part of the circuit should be unlikely to exceed for long periods the current-carrying capacity of the cable (Regulation 433.1.5 refers). This can generally be achieved by:
(i) locating socket-outlets to provide reasonable sharing of the load around the ring
(ii) not supplying immersion heaters, comprehensive electric space heating or loads of a similar profile frog the ring circuit
(iii) connecting cookers, ovens and hobs with a rated power exceeding 2 kW on their own dedicated radial circuit
(iv) taking account of the total floor area being served. (Historically, limit of 100 m² has been adopted.)

Note this is in the appendix it refers to 433.1.5 but often people feel as a result any item over 2kW fixed should have a dedicated supply. For the immersion heater this makes a lot of sense. For the tumble drier also it makes a lot of sense but for washing machine (without built in tumble drier), oven, dishwasher although technically they should have a dedicated supply in real terms the high current draw is for such a short time it's not really a problem.

The immersion and tumble drier are problems because they draw high current for so long. An oven may be on for 4 hours but after 5 minutes it is normally cycling on and off so there is not a great heating effect on the supply cable.
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Postby John125683a » Mon Jan 11, 2016 2:29 pm

Can anybody help or advise me. I cannot find on this Forum the exact question, but the question posed a above is close to my issue.
I have done away with the gas hob and want to fit an electric modern induction hob. I have a 45 amp cooker box/switch wired to main fuse box.
My question is, can I wire the hob to a seperate supply (2.5mm cable),or
should I wire my new electric hob into cooker switch with Oven ?

Thank you, John
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Postby ericmark » Tue Jan 12, 2016 2:16 am

OK to start with some of the rules we have to follow:-
Any cable needs protecting against overload, in the main we do this at the origin but as long as the cable has no branches and is not more than 3 meters long we can fuse at the destination.

In the main an unfused spur drops into this, although some times more than 3 meters. However it needs to end as a fused connection unit (FCU) or socket with the latter the fuse in the plug is the fuse at the destination.

With fixed appliances they don't need to be supplied with a plug and the manufacturer can stipulate protection required 99% of showers for example say you must use a RCD.

Now traditional cooker connections are 32A and unless the manufacturer says otherwise then supplying an oven or hob or complete cooker from the 32A supply is unlikely to be a problem as long as the cable can take that load so 4 mm sq cable. But with a 45A supply that's not normal and although OK for a cooker or hob in the main a stand alone oven will not take the 6 or 10 mm cable required, however using a duel cooker connection unit and a FCU powering a 3kW or less oven is not really a problem.

However where the oven is over 3kW then it's no longer cut an dried. If we could get a 16A FCU it would be great no idea why not made but without them we can't really connect a 3.8kW oven direct to a 45A fuse or MCB that is going OTT.

There is some debate as to induction hob and power requirement, personally I feel an induction hob uses less power than a halogen hob which is next best so even if rated at 32A it is not going to draw that current for long enough to cause the fuse or trip to open. So to my mind having a duel cooker connection unit and 4mm sq cable to both hob and oven is really no problem with standard size hob.

However with a 45A MCB then it does need either a dedicated 16A supply to oven or a FCU which depends on size of oven.

PS always best to start a new thread, I will often ignore threads already answered until I have loads of free time. Unanswered threads I give priority to.
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