Cooker Cable Distance

[Princely]

Is there a limit to the length of cable for the installation of a cooker? The cooker site will require a 3-40 metre run of cable to reach the consumer unit. The cable will run through the loft space with the exception of a couple of metres either end.

Any advice greatly appreciated.

 

[Spark123]

Yes, with any cable there will be a limit for length, wether the limit is caused by volt drop or earth fault loop impedance/protective device. To overcome these limits the cable size may be increased.

 

[Princely]

Thanks, my original post should have stated 30 to 40 metres of cable...is this within limit for a Cooker if I am using normal 30amp cooker wire?

 

[Spark123]

What is the rating of the cooker?

 

[Princely]

I do not know as yet, am awaiting delivery and the website doesn't state a power rating.

It's a built under double oven, the main oven is fan and the hob is separate, I guessing it will be around 12kw in total. Is there a way to calculate the maximum rating I can have based on the distance?

Thanks

 

[DDoyle]

Why would you use "30 amp cooker cable" if your think it is rated at 12kW which is 52A?

More likely the cooker is between 3.5 and 5.5kW (15.5A to 24A)

Further, you need to consider the materials the cable will pass through, such as insulating materials, as you would need to account for this when derating the cable.

If you assume 25A loading then the minimum cable will be 6mm², however if you want to assume your 12kW at 40m, you would need to install 16mm²...

 

[ebee]

Incorrectl.
13KW normally for 6.0 T & E.
Diversety may be applied.
100% of 1st 10 Amps.
30% of remainder.
Add 5 amps if socket on Cooker Control Unit (Occaisional use of Kettle - NOT for washing machine or tumble drier - That`s why I never have a socket there it`s a thro back to olden days)/.
Volt Drop and EFLI are limiting facto9rs for length along with correction factors.

 

[Princely]

Thanks for the replies....I am obviously not giving enough information, can I try again please...

If I ran a 30 amp cooker cable which I believe to be 6.0mm Twin & Earth over a distance of 40 metres through a loft space, (attached to a joist which is not covered by any insultating material and passing through 2 thermal block walls of 4 inches thickness), what rating of oven could I reasonably expect to connect?

Thanks

 

[Adam_151]

Just run the volt drop calc through, and 30A at 40 metres is just on the limit, so you can draw the full 30A through it, but its pushing it, and it'll be wasteing energy

(10mm² would be advantagous (spelling), consider installing it)

EDIT: of course you need to check you can meet disconnect times, for that we'll need to know your Ze (or at least your earthing type) and the type of device you plan to use to protect the circuit

 

[Princely]

Adam, Thanks for advice. I must admit to being lost by your EDIT comments, disconnect times? Ze? If you can let me know what it means I will investigate.

Thanks again

 

[Princely]

Adam, Thanks for advice. I must admit to being lost by your EDIT comments, disconnect times? Ze? If you can let me know what it means I will investigate.

Thanks again

 

[Adam_151]

If a fault to earth occurs, then the circuit needs to be disconencted within a set amount of time, this takes a certain amount of current, and the longer the cable, the more resistance, more resistance equals less current

There is a chart in for reference showing maximum earth fault loop imediance values for different protective devices, this is made up of Ze (the external loop imediance) and R1+R2 (the resistance of the live and earth conductors in trhe circuit)

Ze is measured using a loop tester, if you don't have one of these, you can use the maximum value for your type of supply, its 0.35 for tnc-s and 0.8 for tns, r1+r2 can be measured using a milli-ohm meter, or can be found by looking in tables for cables.

If you don't understand this, can I recommend you read Kevin Boone's guide to cable selection: http://www.kevinboone.com/cableselection_web.pdf ,its quite a lengthy read, but worth it

 

[DDoyle]

Incorrectl.
13KW normally for 6.0 T & E.
Diversety may be applied.
100% of 1st 10 Amps.
30% of remainder.
Add 5 amps if socket on Cooker Control Unit (Occaisional use of Kettle - NOT for washing machine or tumble drier - That`s why I never have a socket there it`s a thro back to olden days)/.
Volt Drop and EFLI are limiting facto9rs for length along with correction factors.

Great Idea, however why do you think people buy double ovens, it usually is not for show. Applying diversity in this situation is not a great idea, you should assume that at least 80% of the full potential load may be applied on a regulat basis, and likley 50% almost daily. When you take into account derating factors and the maximum load for the cable size coupled to EFL considerations, then 6mm² would not be adequate for a 13kW loading, which this almost certainly is unlikely to be anyway.

 

[ebee]

Good answer

 

[Softus]

Good answer

Incorrectl (sic.) - it was a very good answer.