induction hob and cooker circuits

[iamdiydad]

Hi

I am having the following put in:

2 single ovens, each 3.5 kW rated
1 induction 4 plate hob, rated at 7.4 kW
1 domino induction hob, rated at 3.1 kW


I need new radial circuits for these which will be fed from a new consumer unit. Reading the forums I believe I need ...

1 6mm2 T&E with 30A MCB which can feed the two ovens on this one circuit
1 6mm2 T&E with 30A MCB which feeds the 4 plate induction hob
1 6mm2 T&E with 30A MCB to feed the domino induction hob (because the smeg manual states 30A, otherwise would use low rated MCB)


Can anyone see any problems in this?

What RCD should be specified on the supplt side of the consumer unit?#

Many thanks

 

[skenk]

Do you have electric heating and/or electric shower?

 

[Steve]

Hi

I am having the following put in:

2 single ovens, each 3.5 kW rated
1 induction 4 plate hob, rated at 7.4 kW
1 domino induction hob, rated at 3.1 kW

If I were you, I'd forget feeding these from the main CU. Place a new CU in the kitchen (or local to it) and feed all kitchen circuits from here. Feed this CU from a 50A MCB in the main CU or split the tails from the meter. This will make any kitchen alterations easier in future.

I'd put in:
Two 16A circuits each in 2.5mm² for the ovens (with individual 20A DP switches).
A 32A circuit in 6mm² for the big hob (with a 45A DP switch).
A 16A circuit in 2.5mm² for the little hob (with a 20A DP switch).

 

[iamdiydad]

Hi

Yes, but on completely separate consumer units - we have two fully populated CUs and so these new radial circuits would go into a new CU with a new RCD

 

[londonboy]

Do you not have gas?

That is a very large load if you already have electric heating and shower, your risking blowing the main fuse

 

[Steve]

If you're running these circuits from scratch, you should think of ways to alleviate the need for RCD protection. Cookers can be leaky and cause nuisance tripping.

The cooking appliances by their nature DONT require RCD protection, but the concealed unprotected cables do need it. You can get round this by using earthed metal conduit, or protected cables such as MICC and SWA.


I would not fit a RCD incommer to the new CU. Use RCBOs if you have to.

 

[iamdiydad]

Hi Steve

What cable would you use from the main CU to the CU in the kitchen?

Thx

 

[Steve]

That is a very large load if you already have electric heating and shower, your risking blowing the main fuse

You wanna bet? How often will all the cooking elements be ON? How often will this happen when the shower is on? And any electric heating (if storage, never)? How often will this add up to 150A? (a 100A 3036 will pass this for over a minute, nearly 2)

 

[iamdiydad]

Hi

No GAS unfortunately! Oil fired heating, and power shower plus a small electric shower. Then just plenty of lighting circuits and ring mains. Existing single 6mm T&W 32A for current electric cooker which would no longer be used.

Thx

 

[Steve]

Hi Steve

What cable would you use from the main CU to the CU in the kitchen?

Thx

Go for a protected cable if its gonna be buried, or it will need RCD protection at the main CU, which you dont want. SWA or metal conduit, plump for 16mm² for future expansion.

By the way, have a read of the documents here: //www.diynot.com/wiki/electrics:part p and choose whether or not you wish to obey the law

 

[iamdiydad]

Hi Steve

I have part P and am conscious of competent persons etc

I had a quote from a sparky but am looking to validate it as parts were very expensive in my humble opinion and as far as i can see I am looking at a new CU, max 50m of 6mm T&E, plus a few MCBs

Thx

 

[Steve]

What was the quote? What did the quote entail?

 

[Spark123]

What do you mean by "I have Part P"?

 

[iamdiydad]

i have it to read, i myself am not "competent persons" in terms of the scheme, but i certainly understand the basics

 

[skenk]

Presumably you'll aslo be needing back boxes, accessories, grommets, parts for splitting the supply/feeding the new CU, RCD etc. (plus maybe capping, conduit, trunking, plaster . . .) and there will be a mark up for collecting and delivering all the correct parts for you, what price was given for materials?

Proposed circuit design sounds fine to me.