Which MCB for 7.4 kw cooker?

[Welski]

I am replacing a gas fired traditional AGA with a AGA duel fuel Rangemaster cooker.
http://www.rangecookers.co.uk/rangemaster-elan-dual-fuel-product,288.aspx#spec

My electrician is currently on xmas hols and uncontactable. I usually do most of the donkey work myself and he then inspects/does final connections. I have run the cable from CU to cooker point in 6mm through loft space and down through a void in the wall so at no point is it 'buried'. The total run is <10metres. As you can see its a duel fuel electric ovens Max rating 7.4 kw. Gas hob.

He is popping in just before xmas day to ensure we have something to cook on! What I didnt ask him before he left was what rating of MCB did I need to get. The specification doesnt mention anything presumably as cable runs etc are an unknown.

Any assistance would render my life liveable over the christmas holiday !

 

[Cremeegg]

If your "electrician" really is coming in just before Christmas Day then he should have the necessary MCB on his van. How do you know that 6mm cable is adequate? Is the cable RCD protected? You will, of course, have already notified your local authority of this work.

 

[ricicle]

My electrician is currently on xmas hols and uncontactable. I usually do most of the donkey work myself and he then inspects/does final connections.

Ah - that old chestnut (roasting on an open fire)

 

[ban-all-sheds]

20A.

And I hope "wall void" doesn't mean "cavity", as you aren't supposed to put cables in there.

 

[Welski]

My electrician is currently on xmas hols and uncontactable. I usually do most of the donkey work myself and he then inspects/does final connections.

Ah - that old chestnut (roasting on an open fire)

haha I knew you cynical bunch would give me grief. He actually lives in France now having given up on the UK. He used to run a commercial electricity company but no longer keeps anything in the uk. If you care to check my other posts you will see I have a large ongoing project and do most of the work myself. I know everything else is correct as I asked him what I needed before he went off to OZ.

Thanks for the assistance and a happy christmas!

 

[Welski]

20A.

And I hope "wall void" doesn't mean "cavity", as you aren't supposed to put cables in there.

Thanks Ban-all-sheds.

The house is timber framed, the 'void' is a gap between two phases of the building (circa 16th and 17th centuries) its only about 2 foot of the run in there and quite honestly there is no other route for it.

When my 'electrician' rewired my house a few years back he installed a MEMshield CU which if I'm reading correctly is normally used in commercial applications? (He had a lot of gear left over when he packed up his UK business) The MCB's currectly in the CU are EATON MEM2 MCB's following on from that would the correct one to get be part number "MBH120N" ?

 

[securespark]

20A.

And I hope "wall void" doesn't mean "cavity", as you aren't supposed to put cables in there.

20A for 7.4kW?

 

[GaryMo]

That's after diversity has been applied:

10A + 30% full load (another 5A if a socket in incorporated into the control unit) = 19.65A.

Welski, does the cable pass through any insulation in the loft or wall void? If not then I would opt for a 32A MCB.

 

[ban-all-sheds]

That's after diversity has been applied

It's also safe for 6mm² with Installation Method 103....

 

[sparkyspike]

would the correct one to get be part number "MBH120N" ?

That's a double pole breaker I think.

 

[jj4091]

http://www.kevinboone.com/cableselection_web.html

 

[GaryMo]

would the correct one to get be part number "MBH120N" ?

That's a double pole breaker I think.

It's classed as a single pole (120 in the product number) and switched neutral (SPSN).

On SPSN the switched neutral is unprotected, on DP and FP all poles are protected. SPSN are fitted with neutral contacts which make first and break last.

I assume they are two module though as it says "SPSN and DP MCBs can be used in DP distribution boards".

A single pole 20A MCB would be MBH120.

 

[Welski]

20A.

And I hope "wall void" doesn't mean "cavity", as you aren't supposed to put cables in there.

20A for 7.4kW?

I got through to him via the magic of text messanging last night (probably would have been cheaper to employ a local sparky!) and he said to get a 32A one ...I'm confused now.

 

[GaryMo]

Did you miss my post yesterday evening?

Welski, does the cable pass through any insulation in the loft or wall void? If not then I would opt for a 32A MCB.

 

[Welski]

That's after diversity has been applied:

10A + 30% full load (another 5A if a socket in incorporated into the control unit) = 19.65A.

Welski, does the cable pass through any insulation in the loft or wall void? If not then I would opt for a 32A MCB.

The control unit does have a socket incorporated. The wire is clipped to the timber frame with ventilation all round. Even in the void it's not covered at all.