Help with Oven Circuit.

[makken]

Have an existing oven circuit 6mm2 twin & earth from the consumer protected by a 32a mcb goes to a cooker control switch, then 6mm2 from the switch was hardwired in to previous oven. Just bought a brand new oven (single oven that fits in cupboard under worktop) specifications are 2.3kW total electric consumption, max cable length 2m, it specifies for the cable type 3 x 1.5mm2 or equivalent.
Is it ok to wire this one the same 6mm2 straight in to the back of the oven?

 

[somersetsparks]

Well with 2.3kw total consumption, I would say yes. I seem to remember some lengthy discussion on a similar subject last week?

 

[tigerpaul]

Dont forget to derate the breaker!

 

[makken]

Thanks for the quick replies, what size breaker should i size down to?.

 

[somersetsparks]

16A. If the oven has a plugtop on it, you could just terminate the old 6mm to the cooker into a single socket, thus leaving the circuit and fuseboard intact, as well as the oven, as the 13a fuse in the plugtop will provide the protection.

 

[Richard Burns]

The breaker should be fine for that cable, 32A on 6mm is basically usual for cookers.
Your cooker is a low load since it is just an oven and so long as the connectors on the oven are big enough to take 6mm you should be fine.

 

[ACL]

Thanks for the quick replies, what size breaker should i size down to?.

For a total load of 2.3 kw, without diversity you could use a 10A MCB.
What does it say in the instruction manual?
If you leave too high a circuit breaker in place, then the oven won't be protected should a fault occur.

 

[cbw]

WHAT THE BLOODY HELL IS GOING ON HERE?????

Breakers are for protection of cables!!!

Stop giving such rubbish advice!!!!

 

[Richard Burns]

For a total load of 2.3 kw, without diversity you could use a 10A MCB.
What does it say in the instruction manual?
If you leave too high a circuit breaker in place, then the oven won't be protected should a fault occur.

Remember that the MCB protects the cable not the appliance.

 

[cbw]

RB....Perhaps that was put beter than my coment ....But what basic stuff!!!!!!!!!!!!!!!!!!

 

[somersetsparks]

BUT.... You could argue that if you hard wire a 1.5mm2 flex into a cooker switch/outlet, then this is part of the circuit so a lower rated MCb will be required to protect the Cable not the appliance

 

[ACL]

Remember that the MCB protects the cable not the appliance.

I agree except that he's been told to use 3x 1.5mm cable to connect the oven. If he can't get the 6mm into the oven connections, should we not also protect this bit of the cable too?

 

[Richard Burns]

@CBW
Good thing for people to know and a good if slightly OTT response, at least they know now!!

 

[Richard Burns]

BUT.... You could argue that if you hard wire a 1.5mm2 flex into a cooker switch/outlet, then this is part of the circuit so a lower rated MCb will be required to protect the Cable not the appliance

I agree except that he's been told to use 3x 1.5mm cable to connect the oven. If he can't get the 6mm into the oven connections, should we not also protect this bit of the cable too?

The OP asked if the 6mm could go directly into the oven, the 3x1.5mm is the recommended minimum cable size and was not in this case intended to be used.

 

[cbw]

The circuit terminates at the outlet plate.

Thereafter follow MFI and the appliance, its cables and components will be protected by its own fuses/trips etc

 

[somersetsparks]

The OP asked if the 6mm could go directly into the oven, the 3x1.5mm is the recommended minimum cable size and was not in this case intended to be used.

True, true, I'm sometimes guilty of not reading posts proper! I had 1.5mm in my head. I always prefer to use the single socket idea with ovens that come on a plugtop.

 

[ACL]

The OP asked if the 6mm could go directly into the oven, the 3x1.5mm is the recommended minimum cable size and was not in this case intended to be used.

You are correct, my apologies for not fully reading the OP comments.

 

[ACL]

The circuit terminates at the outlet plate.

Thereafter follow MFI and the appliance, its cables and components will be protected by its own fuses/trips etc

The ovens that I have installed over the years have all stated a size for the MCB based on the load of the unit, this has generally been either 16 or 20Amps.
I am in complete agreement that he should check with the MFI.

 

[Richard Burns]

The ovens that I have installed over the years have all stated a size for the MCB based on the load of the unit, this has generally been either 16 or 20Amps.
I am in complete agreement that he should check with the MFI.

I would agree the manufacturers may well have specified a different requirement, with which compliance would be required.

I would have thought most ovens could run on a 16/20A breaker.

However I think we have now lost the OP.

 

[cbw]

You are wrong.

MCB size is based purely and simply on cable size and installation method.

Sorry to be so arrogant. (Also cant spell)

 

[i=p/u]

its fine on 6mm as somone said a minimum of 1.5mm required , you could change the breaker if makes you feel better, just make sure its zs vale is sexy

 

[Guitarist]

You are wrong.

MCB size is based purely and simply on cable size and installation method.

Sorry to be so arrogant. (Also cant spell)

Totally agree mate.
However, if the Manufacturers Instructions state an MCB size, then as long as it will also protect the cable, the MI should be adhered to.

 

[makken]

The exact technical data according to the manual, Voltage 220-240V 50Hz, Total Electric Consumption 2.3kW, Fuse Protection min. 13A, Cable Type/cross Section H05VV-FG 3 x 1.5 mm2 or equivalent, Cable Length 2m. Also states to a double pole control unit with a minimum contact clearance of 3mm in all poles and further stated that Additional protection by a residual current circuit breaker is recommended.

When the manufacturers manual states 1.5mm2 cable, does that mean 1.5mm2 from the consumer unit as most existing cooker circuits are surely going to be wired in 6mm2 (as mine is) or 10mm2.

Should it be wired on the rcd protected side of the consumer?

Anyway i couldn't get the 6mm2 in the cooker terminals so i rewired from the cooker switch in 2.5mm2, so the current circuit is 32a breaker (not on the rcd protected side), 6mm2 T+E to double pole cooker switch (not plug socket type) then 2.5mm2 from cooker switch to cooker terminals.

Could someone clarify if my current circuit is ok and if not what would be the ideal circuit given the specifications i have given.

 

[Swicade]

If the Cooker switch is single plate i'd be tempted to change it for a Switch fused connection unit with a 13a fuse to protect the 2.5mm to cooker.

 

[Strima]

For me I would fuse down to protect the smallest cable. We could go on about unfused spurs and minimum distances etc however where is the cable most likely to receive mechanical and damage through external influences?

As it is a dedicated circuit for one appliance (any socket on the cooker switch?) I would go with 16A MCB (20A if socket fitted). Seems strange they have stated a minimum fuse size but no maximum???

 

[tigerpaul]

You have to protect the cable, so 32a is okay for the 6mm but it wont protect 1.5mm

Check your current carrying capacity tables in the regs to see which mcb is suitable.

 

[tigerpaul]

Yeah they state the minimum fuse size, and then you have to select the cable to suit.

Personally I would go into the oven with 3 core 2.5mm flex, heat resistant stuff would be great to use as well.
Then I'd change the mcb for a 20A one.

 

[makken]

Hmmm, there seems to be varied opinions on what one would do, would i be right in assuming there are different ways to do this and still have a perfectly safe circuit, also what about the manual stating additional protection with an rcd.

 

[Richard Burns]

The exact technical data according to the manual, Voltage 220-240V 50Hz, Total Electric Consumption 2.3kW, Fuse Protection min. 13A, Cable Type/cross Section H05VV-FG 3 x 1.5 mm2 or equivalent, Cable Length 2m. Also states to a double pole control unit with a minimum contact clearance of 3mm in all poles and further stated that Additional protection by a residual current circuit breaker is recommended.

When the manufacturers manual states 1.5mm2 cable, does that mean 1.5mm2 from the consumer unit as most existing cooker circuits are surely going to be wired in 6mm2 (as mine is) or 10mm2. This is specifying the cable from the fixed wiring to the cooker, the one specified is a 3 core flex. Run from the CU would cause problems with the 2m limit, they are trying to ensure that the cable will not over heat.

Should it be wired on the rcd protected side of the consumer? Since the manufacturers recommend it then it should be RCD protected, there may be other requirements in the wiring regulations that mean an RCD must be present, but this would get beyond a simple cooker replacement and start to involve the requirements of the Building regulations, testing and certification of the work and notifying building control as well.

Anyway i couldn't get the 6mm2 in the cooker terminals so i rewired from the cooker switch in 2.5mm2, so the current circuit is 32a breaker (not on the rcd protected side), 6mm2 T+E to double pole cooker switch (not plug socket type) then 2.5mm2 from cooker switch to cooker terminals.

Could someone clarify if my current circuit is ok and if not what would be the ideal circuit given the specifications i have given. An ideal circuit would be a 2.5mm2 twin and earth cable run direct from a 16A RCBO in the CU to a double pole switch (whether fused at 13A or not) and from the double pole switch to the cooker in HO5VV-F flex at either 1.5mm or 2.5mm.

See my comments in your quote above.
As Cbw says the fixed wiring is up to the outlet point so theoretically your circuit is suitable so long as all other requirements for the load / wiring regulations are maintained.
As said above you could fuse down to 13 at/ in place of/ just after the Cooker switch.

The cooker switch meets the 3mm contact gap requirement, as would a double pole FCU.

Please remember that since we have not seen the installation, instruction manual or cooker in reality, we can only give information based on what you have said and the information we give may not be correct.

 

[Guitarist]

Not sure if I've missed anything here, but are you Part P registered? If you are going to alter a circuit in a kitchen then this is notifiable.

 

[makken]

Just one thing though, you say an ideal circuit would be 2.5mm2 t+e from CU but in my case it already has 6mm2 (which i would prefer in case of any future changes), so given that i,m stuck with the 6mm2 if i change to a 16a rcbo at the consumer and stick with the rest of the circuit as it is or would i be better putting a 13a fused unit after the cooker switch?.
Forgot to mention the kitchen is being renovated at the moment and we are using the new cooker on the existing circuit but we will be installing one of those 45a control switch/ plug socket combination units, will that change things other than having to protect it on the rcd side of the CU.

 

[Richard Burns]

I am sorry to say this but the changes you now mention move into the realms of full electrical installation and modifying circuits / cables at both the CU and the Kitchen and this is where further risks come in, the circuit should be designed safely and the requirements of Part P of the building regulations must be met.

The initial query has now moved beyond the point where I feel comfortable supplying any further technical information.

Good luck with the renovation, make sure you are doing this safely and legally, I will now bow out.

 

[Guitarist]

I am sorry to say this but the changes you now mention move into the realms of full electrical installation and modifying circuits / cables at both the CU and the Kitchen and this is where further risks come in, the circuit should be designed safely and the requirements of Part P of the building regulations must be met.

The initial query has now moved beyond the point where I feel comfortable supplying any further technical information.

Good luck with the renovation, make sure you are doing this safely and legally, I will now bow out.

Exactly RB. That's why I have asked if the OP is part P registered, as this is more than a like-for-like change.

 

[Swicade]

Personaly i'd keep the existing cooker circuit as it is and add a 13a switch fused connection unit inbetween the outgoing side of the cooker switch and the oven.....only my personal preference though. The 32a Mcb will need to be changed for a rcbo or preferabley move it across onto the rcd side of the consumer unit.

If your haveing the kitchen renovated and this involves any new socket's/built in appliance points etc the best advice i can give is to discuss all this with the Electrician doing kitchen circuit alterations you have booked in already.

 

[makken]

Many thanks, i appreciate all the help very much considering its my first time on the forum, in answer to the above am i part p registered the answer is no to be honest, i'm a fully qualified plumber with a general understanding of electrics in domestic dwellings and have just started studying part p with the intention of being competent in the near future, however my mate is a fully qualified electrician who works for the local council and whilst i usually go to him with any queries and small jobs that he normally does for me he is currently away on holiday hence my coming to this forum.

 

[makken]

Personaly i'd keep the existing cooker circuit as it is and add a 13a switch fused connection unit inbetween the outgoing side of the cooker switch and the oven.....only my personal preference though. The 32a Mcb will need to be changed for a rcbo or preferabley move it across onto the rcd side of the consumer unit.

Thanks that is what i had in mind

 

[rdelectrical]

is the advice on the instructions saying 3 1.5mm cables designed for the european countries im sure read it somewhere

 

[spark 68]

is the advice on the instructions saying 3 1.5mm cables designed for the european countries im sure read it somewhere

We had a rather long discussion on this a while ago (beko hobs/ovens), and the consensus was that some of these appliances were originally designed for 3 phase use (not UK), as well as single phase hence the 3X cabling requirement.

 

[Guitarist]

Many thanks, i appreciate all the help very much considering its my first time on the forum, in answer to the above am i part p registered the answer is no to be honest, i'm a fully qualified plumber with a general understanding of electrics in domestic dwellings and have just started studying part p with the intention of being competent in the near future, however my mate is a fully qualified electrician who works for the local council and whilst i usually go to him with any queries and small jobs that he normally does for me he is currently away on holiday hence my coming to this forum.

I wish you all the best then mate.
As said earlier, this will be a notifiable job, but don't assume that someone is part P registered simply because they are fully qualified.