Swap Gas Hob for Ceramic Hob

[atm-12]

Hi, I am a newly qualified spark and I just want to confirm I am doing this small job correctly.

The job is to swap my grandmas cooker and hob. At the minute she has a gas hob and electric cooker. There is a 10mm cable supplying a 45A switch with socket outlet backed by a 40A breaker. At the moment the cooker is wired in 2.5mm flex from the 45A switch direct to the cooker with the hob being plugged in on a 13A plug. I believe this is wrong as the 2.5mm cable from the 45A switch to the cooker is fused at 40A with the maximum load of the cable 20A?

The new cooker I am installing is 2.9kw and the hob is 6.5kw with the cable run being a maximum of 10m. That gives me a total load of 40.87A so the 40A breaker and 10mm is ok.

What I have in my head is to hard wire the hob into the 45A switch with 10mm and wire the cooker in 1.5 flex on a 13A plug top. The load for the cooker is 12.6A, is this to close to 13A?

Ideally I would run a seperate 20A supply for the cooker but want to avoid chasing down the wall if possible.

Also, would it be possible to wire from 45A to cooker in 6.0mm. I dont think it will because its fused at 40A and 6.0mm wont be big enough. Please correct me if I'm wrong.

Thanks in advance for any help.

 

[Deleted member 9648]

Run a 6.0mm from the 45a switch to a low level cooker connection unit and connect the hob in 6,0mm....you'll struggle to get a 10mm into the hob connections. Loop a 2.5mm from the incomer side of the LL connection unit into a 13a socket for the oven.Mount these on two surface boxes butted up to each other. Replace the existing 40a breaker for a 32a....remember diversity on cooking appliances means they will never draw maximum current for any length of time if ever.

 

[Leesparkykent]

10mm from load side of 45A switch to a dual box with a cooker outlet plate and on the other side a 1g socket. 4mm to the hob from the cooker outlet plate and plug the cooker in. No need to change the mcb.

 

[davesparks]

Dual cooker outlet plate connected to the cookerswitch via 10mm T&E
6mm from one outlet to hob
2.5 from the other outlet to the oven

All done and compliant without hiding 13A fuses where nobody can get to them or adding extra cables to a finished kitchen.

 

[Dave OCD]

I'd do the final connection to the hob in 4mm 3 core HO7 type flex too as it'll probably get way too hot under there for T&E over time.

 

[andyb]

I'd do the final connection to the hob in 4mm 3 core HO7 type flex too as it'll probably get way too hot under there for T&E over time.

I use this as well, easier to terminate too.

 

[Deleted member 9648]

Dual cooker outlet plate connected to the cookerswitch via 10mm T&E
6mm from one outlet to hob
2.5 from the other outlet to the oven

All done and compliant without hiding 13A fuses where nobody can get to them or adding extra cables to a finished kitchen.

Best check the oven requirements first,often these are designed to be fused at 13a via a plug.

To the OP all of the above are acceptable,personally I would still run 6.0mm from the 45a switch and drop to a 32a MCB if only because 10mm is a pig to terminate in a single box size accessory.

 

[davesparks]

Best check the oven requirements first,often these are designed to be fused at 13a via a plug.

Hahaha, you're kidding right? Appliances are not protected by plug fuses, cables are!

An oven is a fixed load not requiring over current protection, so cable size can be based entirely on the load current and not the nominal current. Plus the cable behind a built in oven is pretty well protected from mechanical damage, so what really is the problem?

 

[Deleted member 9648]

Hahaha, you're kidding right? Appliances are not protected by plug fuses, cables are!

An oven is a fixed load not requiring over current protection, so cable size can be based entirely on the load current and not the nominal current. Plus the cable behind a built in oven is pretty well protected from mechanical damage, so what really is the problem?

I realize that,but some single ovens come with a fitted 13a plug....so I would suggest any other method of connection would be against manufacturers requirements. I didn't say there was a problem did I?,just to check manufacturers requirements....is it time of the month or something?

 

[davesparks]

I realize that,but some single ovens come with a fitted 13a plug....so I would suggest any other method of connection would be against manufacturers requirements. I didn't say there was a problem did I?,just to check manufacturers requirements....is it time of the month or something?

You said that ovens are often designed to be fused at 13A by a plug, high is a nonsense as the oven will not be fused (protected) by the 13A plug fuse, only the cable. Ovens are protected by their own internal protection (the overheat stat usually)

Time of the month, No, just ****ed off with the ridiculous bowing down to nonsense printed in manufacturers instructions and the mistaken belief that appliances fitted with plugs must never a have their plugs cut off.

 

[Deleted member 9648]

You said that ovens are often designed to be fused at 13A by a plug, high is a nonsense as the oven will not be fused (protected) by the 13A plug fuse, only the cable. Ovens are protected by their own internal protection (the overheat stat usually)

Time of the month, No, just ****ed off with the ridiculous bowing down to nonsense printed in manufacturers instructions and the mistaken belief that appliances fitted with plugs must never a have their plugs cut off.

Your splitting hairs mate....fair enough....but the point I was making is that some ovens come with a fitted 13a plug and therefore the manufacturer intends them to be plugged in.....and whats wrong with plugging an oven in? I do realise that a fuse protects the cable not the appliance!

 

[Englishman]

Run a 6.0mm from the 45a switch to a low level cooker connection unit and connect the hob in 6,0mm....you'll struggle to get a 10mm into the hob connections. Loop a 2.5mm from the incomer side of the LL connection unit into a 13a socket for the oven.Mount these on two surface boxes butted up to each other. Replace the existing 40a breaker for a 32a....remember diversity on cooking appliances means they will never draw maximum current for any length of time if ever.

A lot of built in ovens don't have the space available for a surface box and plug top. Have had to hard wire the cooker flex and change the plug top to a 13a FCU a few times due to lack of space. And that's with boxes chased in.

 

[Deleted member 9648]

A lot of built in ovens don't have the space available for a surface box and plug top. Have had to hard wire the cooker flex and change the plug top to a 13a FCU a few times due to lack of space. And that's with boxes chased in.

Either that or stick it in an adjacent unit.

 

[Deleted member 9648]

Regarding the point about the fuse protecting the cable,not the appliance. Manufacturers don't always see it that way,think of the regular manufacturers requirements for 3a fuses on fans....and boilers to name but two.

 

[Midwest]

just ****ed off with the ridiculous bowing down to nonsense printed in manufacturers instructions and the mistaken belief that appliances fitted with plugs must never a have their plugs cut off.

Have to disagree with you there. I know this has been argued before, and I posted a link where manufacturer specifically stated warranty would be voided if their moulded plug was removed. Can't find it again, but it was a tv, Samsung I think.

Which may not be a comparable appliance, however I've just had to replace our dishwasher. The electrical connection instructions;
+ the connection may only be modified by technicians
+ a power cord extension may be purchased from customer services
+ if the power cord is damaged it must be replaced with a particular cord. To prevent injury, the power cord may be purchased from customer service only.

(The power cord in question is fitted with a moulded plug top one end and connector block the other end, to be inserted into the appliance).

Warranty;
We reserve the right to invalidate the warranty: -
a. If repairs or other interventions are performed by persons not authorised by us to take such action,
or if our appliances are fitted with non-original spare parts, extras or accessories'

So I think you do need to read the manufacturers or you could void the warranty.