IS this Ok?

[dazalock]

Hi

Wondered if someone could cast an eye over this setup for me.

Intitially had a standalone cooker on a 30amp circuit.

Have replaced the cooker with a electric HOB and a single oven. The Oven is rated at 2.5 KW and the Hob is about 6KW. The equates to about 35 amps, but as I understand it, this is ok as it is assumed not all rings will be burning at once with the oven on. Ive run a 6mm cable from the juction box to the hob (which in turn has a 6mm cable to a cooker switch within 2 meters of the cooker) and a 2.5 mm cable from the oven into the same junction box.

many thanks for any remarks.

 

[felix]

Your oven should really be on a 13 amp fused spur. You can feed this from that junction box with 6 sq mm cable or you can put it on your ring main.

 

[dazalock]

Thanks Felix, so, if I used 6mm cable to the oven, which is the same size as the existing, would I still need a fused spur?

I have thought about putting it on the ring main, but, seeing as the oven would draw 10amp, I thought that would leave little for everyting else.

Would appreciate any thoughts.

Regards

 

[greencoat]

Felix is saying use 6sq mm from the JB to the fcu, not 6 sq mm to the oven.

[I am watching this post with interest as I've just found our (same as yours) cooker rated at 2550W connected to the cooker radial on a 40A mcb........
oh dear]

<edit - I also think heat resistant flex should be used because the book says cables should be able to withstand ambient temps. of 75 deg. celcius >

Julian

 

[dazalock]

Hi Julian

"Felix is saying use 6sq mm from the JB to the fcu, not 6 sq mm to the oven."

I took it that he was saying that I could use the 2.5mm to the oven as long as it went into a FCU and then 6mm to the Junction box, I can understand this as the 2.5mm is only rated at 15A and could melt if there was a problem on the 30A cable, thus use a FCU downstream to protect it. However, instead of doing this, could I just use 6mm direct to the oven and therefore all cable on the same rating.

"I've just found our (same as yours) cooker rated at 2550W connected to the cooker radial on a 40A mcb........
oh dear] "

Excuse my ignorance, but, So? A 2550W cooker only equates to aboyt 11A, well below your 40A mcb, so should be safe?

Regards.

 

[supersparks]

as long as the run is short you could use 2.5mm from the junction box/ load side of the Cooker control then to a FCU.

the 2.5 is protected by the 13a fuse.

best not to have the 2.5 too long between supply and FCU..

 

[felix]

You can use 6 sq mm cable all the way to the oven if you like but what size is its internal wiring? Is it good for 30 amps???

As for Supersparks' idea of using 2.5 sq mm from the junction box to an FCU, this should be OK. It happens in practice when you put a spur onto a 30 amp fused ring using 2.5 sq mm cable. You rely on the fact that you are unlikely to overload the cable with anything you could connect to the end of the spur. This will also be true of your oven thanks to the 13 amp fuse in the FCU.

 

[greencoat]

Dazalock said

Excuse my ignorance, but, So? A 2550W cooker only equates to aboyt 11A, well below your 40A mcb, so should be safe?

What I mean is you don't protect an 11A circuit with a 40A fuse, you use the closest above it don't you. Even though disconnection times are 0.4 s the full 40 A has to flow through the cooker for the mcb to trip, which could well destroy the cooker.

Julian