Do I need a new circuit for my new cooker?

[totallygreen]

Hi all.

I'm totally new when it comes to electrics so please go easy on me!

Our oven needs replacing and today I had an electrician over to give me a quote, as the oven I was hoping to buy is supposed to be "connected to the mains". The electrician briefly looked at my oven switch and said he thought it was just pulled from the socket and that I'd need to have new wires drawn to the main board (which I'm assuming is expensive, he was a bit vague on the total there) if I was going to get an oven over 3 kW (absolute max). The oven I wanted to get is a zanussi and is 3.5 kW, although I found a nice electrolux at 3 kW... The electrician was generally nice and helpful, but he seemed to pay no heed to the fact that I needed to keep costs down and kept suggesting more (and thus more costly work on the various things I need done) - of course this may have all been sound advice, but I don't want to be taken for a ride as I haven't got the first clue about these things.

What has me confused is that the oven that was already built in (by the previous owners, a 2.8 kW whirlpool) has its own switch with a little box next to it which says "fuse", yet there is no dedicated cooker fuse on the main electric board. Is it not possible then that this is a dedicated circuit (which could handle more than 3 kW - or at least handle that much safely and reliably)? I just don't get why there'd be a designated cooker switch if it didn't isolate the cooker...

I've attached a picture of the cooker switch - any thoughts/help/advice is greatly appreciated!

Untitled

• totallygreen
• 10 Dec 2012
• 1

p.s. unrelated to the socket issue, but another issue re needing-a-new-cooker: The old installation has a whirlpool gas hob (which works perfectly well) and the instructions for that say any oven underneath should be (a) fitted with a cooling fan, and (b) made by the manufacturer.
Now, (a) doesn't seem implausible - but wouldn't any modern cooker have a cooling fan? (The biggest problem with the old oven was that it would overheat - just running by itself, no hob - and the fan shut down, or the other way around, either way the control board sometimes stops resonding). But does (b) sound like something I need to go by, assuming any cooker has enough room and there's the required insulating space underneath the gas hob? I'm not a fan of whirlpool after my oven troubles.

 

[ericmark]

Following the regulations there are two limits cited.

Over 2kW it should have a dedicated circuit although it does not say must and it is up to the electrician to look what else is connected to same circuit.

Over 3kW it must have it's own circuit basic fact 3kW is limit of a 13A fuse so after that no option.

In Europe they don't have 13A they have 16A and there are ovens made for Europe which fall between 13A and 16A really do very little different to those below 13A but can cost a lot more to wire up.

There is also the point that new circuits need RCD protection so if there is not already an RCD fitted it's not simply a new circuit but also a RCD is required. Again under 13A (3kW) can be combined with fuse over 13A needs a special box.

So if you want to keep down costs then make sure the oven is under 3kW (13A) often it's a case of above 3kW the two elements are on together with one option but below they time share which really makes very little difference to cooking. So my oven with 32A supply (stand alone) has 13 options on selector switch and my mothers built in under 3kW has 7 options on selector switch.

 

[totallygreen]

Following the regulations there are two limits cited.

There is also the point that new circuits need RCD protection so if there is not already an RCD fitted it's not simply a new circuit but also a RCD is required. Again under 13A (3kW) can be combined with fuse over 13A needs a special box.

So if you want to keep down costs then make sure the oven is under 3kW (13A) often it's a case of above 3kW the two elements are on together with one option but below they time share which really makes very little difference to cooking. So my oven with 32A supply (stand alone) has 13 options on selector switch and my mothers built in under 3kW has 7 options on selector switch.

Thanks for replying! Unfortunately I'm so green I'm not getting much sense from the two paragraphs quoted... what is RCD? And does the second paragraph mean there is a cheaper option than running wires through the ceiling to the main board? Also, is an exactly 3kW oven okay, or would that be pushing it?

I take it you're agreeing with the electrician in saying the "cooker switch" is only fluff?

Again, thanks for taking the time - I really appreciate it!

 

[ericmark]

Sorry missed fan question. This is one reason the oven should never be switched off the fans keep it cool. One would hope that if the power went off when cooking the Christmas Turkey it would not do any damage however this would depend on the build of the carcass and after 5 hours getting everything so hot it could be a problem.

Near every oven now has a cooling fan except the silly gas things. Hobs also now often have cooling fans to keep the electronics cool although the modern hob is no where near as hot as the old types as the heat goes directly into the pan and does not heat the hob first.

Old gas hobs of course will work without electric power so in real terms it's only a problem when mixing gas with electric.

Older electric hobs do get hot the cool type are called induction. My induction will boil a kettle worth of water in a pan faster then the electric kettle but old electric and gas are no where near as fast and the surface gets hotter. I can put £5 between hob and pan boil water and £5 undamaged but can't do that with old electric or gas.

 

[EFLImpudence]

Do you have a cooker switch above the worktop?

Find out which fuse or mcb in your consumer unit (fuse box) turns of the oven socket and note what other sockets (if any) also stop working.

Can you post a picture of your consumer unit so that we can see all the circuits?

 

[ericmark]

The rules on isolators (Cooker Switches) are not really electrical rules but heath and safety rules. Think about it, should a chip pan go on fire then you want to be able to switch off the cooker somewhere that does not put you in danger and yet local to cooker so it can be done quickly.

Because the manufacturers tell you in the instructions to fit an isolator then since the electrical rules say you must follow manufacturers instructions then it is covered by the rule book but in a round about way.

3kW is the limit and a cooker which states it's 3kW can be connected to a fuse connection unit (FCU) but a cooker at 3.2kW can't be connected to a FCU. However saying that all fuses get hot and although a 13A fuse run to the limit is a FCU is OK the same fuse in a 13A Plug has problems due to radiating the heat it produces so items which run for a short time like the kettle are OK but items run for an extended time like an immersion heater can't use a 13A plug but can use a 13A FCU.

This does make a difference with ovens as often for maintenance you want it to plug in so you can easy remove it for repairs. Using a 13A plug the plug needs to be in free air and visible. However using the old 15A plug which does not have a fuse built in and a FCU feeding the socket means we can have the 15A socket hidden in the oven shell. Although not really something I would want to do I like plugs to be visible.

So to answer question 3kW and under is what to look for avoid any over that limit even if just 3.1kW.

As to RCD these are devices which should if one gets a shock turn off the power. Will not stop you getting a shock but will limit time to 40ms so unlikely to kill you. These devices are now required for new installations with a plug and socket under 20A or except with special cable the cable is buried in the wall.

In real terms using what you already have is no problem but putting in something new has to follow the new rules.

The problem is to fit a mini box (consumer unit) with just one RCD is likely to expand over the years to a whole array of little boxes. And to fit two boxes is likely the same price as to remove the existing box and replace it with a new box covering all circuits. So it is common for electricians to try and get the home owner to change the whole unit as they know in the long run it will save the home owner money and it also makes the whole home safer.

However under the magic 13A or 3kW these units can be built into the FCU so you have a RCD FCU. This is far cheaper than fitting a mini consumer unit. So again keep oven to 3kW or less.

With my mother the cooker cable was run around the outside of the house. OK special cable called SWA but point is there are often other options one hopes a good electrician will judge what is best for you but of course he can get mislead. Walk into a kitchen and see new appliances everywhere then one assumes the person has the money for a future proof job. Asked to connect in a second hand free cycle oven and one looks for cheap option. It's not a case of getting extra money but saving time explaining all the options and if you ask then likely he will take the time to explain.

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