How can i work out the size of cable for cooker?

[PingCrosby]

I need to replace my current (broken) cooker.

The cooker currently in use is a Zanussi ZHF865X and is rated at 5.5kw which i calculate as ~23amps (5500/240). The currnt circuit breaker attached to this ring is a B30 (which i assume is a 30amp breaker). This seems massive overkill and surely is wrong? By the time it breaks wont the cable have melted??

Looking at the cable from the wall to the cooker i think it is 6mm (to be honest it is very hard to tell with my limited experience). How can i tell?

--- So onto my question --- (finally)

I am contemplating replacing my oven with a Indesit FIU20IX and all i can find about this cooker is that it is a class C - ( i think it is 7000kw) , which means 30amps.

Does a class C oven mean it is rated at certain kw??

I guess i really need to understand the size of cable that is already installed (not the cable to the cooker) - looking in the CU box I could not make head-nor-tail of it ? - and i dont want to mess/touch that ?

How is cabling actually measured - i thought it would be a cross section but it makes no sense I cannot tell if the current cabling is 6mm or 4mm etc?

Sorry for this long drawn out post

And thanks

 

[flameport]

A B30 is a 30 amp breaker. This will be sized to the cable, NOT to the appliance on the end. It is there to protect the cable.

A Class C just shows how efficient it is at using energy, class A being the best. 7000W will be the total power of all the elements added together - when in use, the total power will be significantly less as the elements won't all be on at the same time.

The cable size is the cross sectional area of the wires. For a 30A breaker, the cable should be at least 6mm.

Provided the circuit was installed properly to start with, all you need to do is just swap over the cooker - no need to change anything else.

 

[PingCrosby]

The cable size is the cross sectional area of the wires. For a 30A breaker, the cable should be at least 6mm.

That was what i was looking for... As the old cooker was only 5kw then 4mm cable would have sufficed - so I was guessing that the 30amp breaker could be overkill...

When calculating the x-section of the wire..if its multistranded cable is it the size of all wires combined?

 

[sparkiedave]

also depends on the length of cable, 4mm cable will carry 32amps but most sparks put 6mm in for cookers to be on the safe side and allow for bigger cookers being installed later

 

[RF Lighting]

When calculating the x-section of the wire..if its multistranded cable is it the size of all wires combined?

Measure the diameter of one of the strands with a micrometer.

Divide that by two for the radius

Pi multiplied by the radius squared gives you the CSA of one strand

Multiply that by the number of strands, and that's the CSA of your cable.

 

[ban-all-sheds]

That was what i was looking for... As the old cooker was only 5kw then 4mm cable would have sufficed - so I was guessing that the 30amp breaker could be overkill...

As flameport said, the breaker is related to the cable size, not the appliance rating (although obviously the latter does impose a minimum rating for the first two).

See this: //www.diynot.com/forums/viewtopic.php?p=81696#81696

It could be a 100A breaker as long as the cables are adequate.

Measure the diameter of one of the strands with a micrometer.
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Alternatively, measure the diameter of the whole bunch with a 0.1 resolution vernier caliper and calculate from that. As cables come in a limited range of fixed sizes you'll always be able to tell which you've got.

 

[PingCrosby]

also depends on the length of cable, 4mm cable will carry 32amps but most sparks put 6mm in for cookers to be on the safe side and allow for bigger cookers being installed later

This is my issue really -- I do not want to take the risk ! I need a definitive way of knowing, but just looking at the cable itself i have no way of knowing.

Should i just buy 1" of 4mm & 6mm cabling and compare? Is this really my only option? I am sure its not 4mm but i need to be on safe side

 

[ban-all-sheds]

Are you talking about the circuit cable, or the one from the outlet plate to the cooker?

What type is it?

Which of the conductors are solid or stranded?

What are its overall dimensions?

If everything is currently on a 30A breaker, why do you think it might have been wrong all these years?

 

[PingCrosby]

Are you talking about the circuit cable, or the one from the outlet plate to the cooker?

I am talking about the circuit cabling

Which of the conductors are solid or stranded?

As far as i can tell the L & N are stranded -- I need to remove the wall junction box cover and look at the circuit cabling to be 100% certain tho.

What are its overall dimensions?

Sorry I do not quite understand this one .. Overall dimensions of ??? the sheathing or the cable itself?

If everything is currently on a 30A breaker, why do you think it might have been wrong all these years?

Ahh this one is easy to answer. Having previously checked the other wiring in my home - it would seem that whoever did the work used whatever cable was available and was a tad slap-dash. For example there has been wiring where the earth has not been sheathed, earth used as a live because no one could be bothered to buy 3m of the correct cable, missing earths (on metal fixings etc), embedded junction boxes in the plaster - list goes on..

Basically its a confidence issue?? I have very little confidence in the current wiring.

AFAIK - 4mm cable 36 amp's, 6mm cable 46amp's - but what i do not know is how the cable length affects this. Point-to-point to the CU i would guess 8metres.

Ps..Thanks to everyone who is helping me thus far

 

[bongos]

AFAIK - 4mm cable 36 amp's, 6mm cable 46amp's - but what i do not know is how the cable length affects this. Point-to-point to the CU i would guess 8metres.

The maximum load the cable can safely take will also be affected by the installation method (whether in plaster, through insulation etc). This can actually vary quite alot.

The length of the cable will affect volt drop. If the cable is too long you will be below the accepted voltage at the appliance.

Another problem with a long cable run to an appliance is that the earth fault loop resistance will increase because the earth fault loop path is longer. If this becomes unacceptably high then your fuse/MCB will not protect the cable correctly. With a run of 8m this is unlikely to be a problem.

But if the wiring is old and you have little faith in its installation it might be time to get someone to check it.

 

[The Dentist]

Should i just buy 1" of 4mm & 6mm cabling and compare? Is this really my only option? I am sure its not 4mm but i need to be on safe side

Go and have a look at the cable in one of the DIY sheds and compare it to what you have

 

[sparkiedave]

if there is enough cable spare, nip a bit off the end and take it to a wholesalers and ask them

 

[ban-all-sheds]

Or look at the info here: //www.diynot.com/wiki/electrics:flatpvccables