10mm cable and 6mm cable

[andycc123]

Hi i am just wondering if i am safe with this wiring, i have 10mm cable coming out of the consumer unit with a 40 amp fuse and after 4 metres the cable has a box with 3 64amp connectors joining a piece of 6mm cable wich then runs down to the oven.

I just want to make sure that the connections are safe and that the 10mm cable isnt going to burn the 6mm cable using a 40amp fuse with ony an electric double oven connected.

 

[Chri5]

What is the ovens max electrical load, and what is the distance of the cable cu to box, box to cooker switch and on to oven?

Google the oven maker and you should find details of kw load

 

[EFLImpudence]

I just want to make sure that the connections are safe and that the 10mm cable isnt going to burn the 6mm cable using a 40amp fuse with ony an electric double oven connected.

It would be the other way round but the answer is still - NO, it won't burn the other cable.

Is the 10mm² in conduit or thermal insulation by any chance?

 

[ricicle]

It would be the other way round but the answer is still NO.

Why not ?

 

[EFLImpudence]

Why not ?

Well, one cable isn't going to burn another

but if one were to overheat it would be the 6mm²

or did I misunderstand your query?

 

[ricicle]

Sorry I thought you were saying no as in it wasn't ok.

 

[EFLImpudence]

Ok.

I'll clarify it.

 

[PrenticeBoyofDerry]

Hi i am just wondering if i am safe with this wiring

Lets see?

i have 10mm cable coming out of the consumer unit with a 40 amp fuse and after 4 metres the cable has a box with 3 64amp connectors joining a piece of 6mm cable wich then runs down to the oven.

Providing the cable does not encounter any thermal insulation and cooker is not a further 35 metres away from the connection it should be safe.
Obviously we assume continuity, insulation resistance, polarity, Ze, Zs, PFC and RCD tripping times (if applicable) are okay.

I just want to make sure that the connections are safe and that the 10mm cable isnt going to burn the 6mm cable using a 40amp fuse with ony an electric double oven connected.

Should not burn cable even if on full load, providing as above.
As for connections, they should be checked that there is good contact with conductive core and terminals are tight. This should be done with power off and you have safely proved the circuit is dead!

 

[JohnW2]

Isn't this discussion getting a bit carried away with itself? Am I wrong in saying that, assuming we are, as stated, dealing with an oven, rather than a cooker (and assuming that fixed loads generally can't result in overloads), there's surely no way that 6mm² cable would be at the slightest risk of overheating - even 2.5mm², with the worst possible installation methods (or even 1.5mm² with most installation methods!), would probably suffice! - and the 40A MCB would surely provide adequate fault protection for 6mm² cable.

Kind Regards, John.

 

[EFLImpudence]

Isn't this discussion getting a bit carried away with itself? Am I wrong in saying that, assuming we are, as stated, dealing with an oven, rather than a cooker (and assuming that fixed loads generally can't result in overloads), there's surely no way that 6mm² cable would be at the slightest risk of overheating - even 2.5mm², with the worst possible installation methods (or even 1.5mm² with most installation methods!), would probably suffice! - and the 40A MCB would surely provide adequate fault protection for 6mm² cable.

That's what I meant by "No".

 

[JohnW2]

Isn't this discussion getting a bit carried away with itself? Am I wrong in saying that, assuming we are, as stated, dealing with an oven, rather than a cooker (and assuming that fixed loads generally can't result in overloads), there's surely no way that 6mm² cable would be at the slightest risk of overheating - even 2.5mm², with the worst possible installation methods (or even 1.5mm² with most installation methods!), would probably suffice! - and the 40A MCB would surely provide adequate fault protection for 6mm² cable.

That's what I meant by "No".

There are times when I get a bit jealous about some people's power of brevity On t'other hand, a bit of explanation sometimes doesn't go amiss!

Kind Regards, John.

 

[PrenticeBoyofDerry]

"The power of brevity" now we getting mathematical!

 

[andycc123]

the cable from the oven to the switch is 1.5m long, from the switch to the connection box it is approx 5m long, and 4m from the connection box to the cu. All the cable apart from the 4m to the cu box is 6mm. All of the cable has the grey covering.

If i can go smaller on the fuse can you let me know as i have a 30amp fuse spare and if it will be safer and still work without affecting i would rather do that to make it slightly safer.

The oven spec is 4.8kw elec connection, 0.99kwh on main oven and 0.79kwh on second oven.

Thanks to all who have been posting this is all helpfull information.

 

[PrenticeBoyofDerry]

The output rating of your oven suggest that a protective device of 20Amp would be suitable.
The distances given will not offer any voltage drop issues, the only other considerations would be the method in which the cable is run or contained and fuse type.
Does the cable run through thermal insulation, is it contained within trunking/conduit what type of fuses are they (BS number)?
With the information you have offered so far, the installation is not unsafe as it stands. The fuse is there to protect the cable of the circuit even though higher than required, should not pose any problems. The advantage of already having 6mm cable in place does give you allowances for a higher output upgrade of oven in the future if required.
Ideally the whole circuit is best run in the same sized CSA of cable but this does not make it electrically unsafe.

 

[JohnW2]

Ideally the whole circuit is best run in the same sized CSA of cable but this does not make it electrically unsafe.

Other than the fact that it avoids a join (which could be present even if the cable were all the same CSA) what considerations make you feel that it is less-than-ideal to have two different CSAs (provided, of course, that the OPD is appropriate to the cable of lower CSA)? As ericmark wrote yesterday in another thread, having a cable run partially in a cable of higher CSA may sometimes be of value in relation to voltage drop or loop impedance.

Kind Regards, John.