Replacing flex on a Bosch built-in oven

DavidA1982 · 25 Sep 2012

Hi all

I am doing up my kitchen and have run out of money, so bought a second-hand built-in Bosch double oven. Model number is HBN13M250B - it's a double oven.

The oven has come with a length of twin and earth cable fitted (with a plug on the end, which is a bit worrying!). I could just remove the plug and connect the cooker to the cooker connection point with the twin and earth, but I've actually got a metre of heat-resistant flex in the cupboard that I'd rather use. My problem is, I cannot for the life of me work out how to disconnect the cable from the back of the oven! Should be simple, but after 30 minutes of playing with it I just cannot work it out. I will try to get a picture posted to show how it connects, but the cable feeds in to a white plastic connection plug thing, and it looks like this plug would pull out but I cannot work out how.

I've scoured the internet for installation instructions but found nothing. This is a pretty specific question, but if anyone has installed a bosch double oven and has had to change the cable then hopefully they can help me!

(BTW, I have had an electrician in to install a dedicated circuit for it, and I've checked with him and he is happy for me to connect it up myself).

martinxxxxxx · 26 Sep 2012

Wrong! your electrician should be telling you that if the cooker was supplied with a moulded plug incorporating a fuse, you should not be removing that fuse protection and putting it into a Cooker connection unit.
The cable (if it is manufacturer supplied and fitted) will be adequate to use. You need a socket to put it in OR a fused connection unit.
This way you are not lowering the fuse protection to the oven.
The socket/FCU needs to be accessible or controlled by and accessible switch

DavidA1982 · 26 Sep 2012

Thanks. I bought the cooker second-hand. It is a double oven and so a plug is unsuitable and was definitely added by the previous user. I suspect the cable was too. I want to replace it with heat-resistant flex, because that seems a lot safter than simple twin and earth to me.

The FCU and switch is all done properly - the electrician has done it and tested etc.

Taylortwocities · 26 Sep 2012

This model is discontinued so cannot find any details,.

What is the rating of the oven. There should be a rating plate on the back of the oven, or on the edge of one of the doors.

The rating may in amps(A) or kilowatts (kW).

Need to know this to advise on the right cable size.

Peet · 26 Sep 2012

There's a user manual for it here:
http://www.espares.co.uk/datastore/ProductManuals/902208.pdf

The stuff in the back still doesn't tell you what the cable gauge is though.

Look at the plate on the back of the oven, or if it's hard to move, open the doors on it and look at the side of the unit normally covered by a closed door for a lebel and let us know the rating of it. The spare parts sites simply list one of the elements in it as 2300W but they'll be another and maybe a grill too. Then take a pic if possible of the whole of the back of the oven and post it.

A double oven like this one is highly unlikely to belong on a plug.

Looks a nice oven. Better to buy decent 2nd hand, than cheap new.

JohnW2 · 26 Sep 2012

Peet said:
The spare parts sites simply list one of the elements in it as 2300W but they'll be another and maybe a grill too.

There were thre variants of this oven (/01, /03 and /10) which causes a little confusion, but if you look at the Bosch Spares site, you'll find, for all three, Main/Fan Oven elements at 2300W and 2100W and Grill/Oven elements at 2200W.

I therefore presume that there are just two elements, and that the whole oven is somewhere in the 4300W - 4500W range. That's approaching 20A and, although that amounts to only 13A if one applies the ususal 'cooking appliance diversity', as you say, I don't think anyone would really put (or be advised to put) such an oven on a 13A plug.

Kind Regards, John

EFLImpudence · 26 Sep 2012

If the circuit is protected by a 30A fuse/32A mcb ...

... use 4mm² cable connected to the outlet plate then the rating of the oven doesn't matter.

Also, you will need two metres.

DavidA1982 · 1 Oct 2012

All,

Many thanks for the responses, I really appreciate it. I've been away from home for a few days but just checked - it's 4.4mw.

It is going on a brand new circuit with a 30a fuse.

I should have been clearer in my original post - it was never my intention to use a plug on this thing, it would be entirely unsuitable. The plug was put on by the previous owner - a quick check through my previous emails shows that he did this just so I could see it working when I picked it up.... which is a relief! See the attached pic of the plug and you will see what I mean!

Untitled

DavidA1982
1 Oct 2012
1

The "problem" I'm trying to fix is that the cooker is fitted with twin-and-earth cable, and not heat-resistant flex. I thought it was better to fit heat-resistant flex (although I've only got one metre of the stuff which was taken off a freestanding electric cooker - power rating unknown). What I'm trying to work out is how to disconnect the existing cable and put in the flex. I attach a picture of how the existing cable is connected. You can see a plastic plug that screws out of the white plastic contraption, but this doesn't seem to help. Any ideas?

Untitled

DavidA1982
1 Oct 2012
1

Or should I just give up, and connect the oven to the connection point with the existing twin-and-earth?

Thanks!

flameport · 1 Oct 2012

The white item is just a cable grip - the middle unscrews to release the cable.
There will be a separate plate or cover to get at the actual wiring terminals, usually located above or next to that white item.

Peet · 1 Oct 2012

If that manual is the right one, and it looked like it was the right one, it says 'Connection have to be made using a mains connection cable not lighter than H05RR-F 300 V / 500 V Rubber Flexible Cable or H05VV-F 300V / 500V PVC Flexible Cable.'

H05RR-F is this stuff
http://www.eland.co.uk/documents/H05RR-F Cables.pdf

And what it means by 'not lighter than' I don't know as that spec doesn't determine a CSA. See EFLI's post for cable CSA.

BS6004 T&E is specced to 70degC looking at some of the data here. Although you'd derate it those temps.

When you fit it make sure the cable isn't trapped or deliberately contacts the oven's enclosure.

securespark · 1 Oct 2012

From the PDF:

WARNING: Connection and first start of the
appliance may only be performed by an
authorised specialist.
Connection have to be made using a mains
connection cable not lighter than H05RR-F
300 V / 500 V Rubber Flexible Cable or H05VV-F
300V / 500V PVC Flexible Cable.

EDIT: SORRY! I had the same idea as you, but spent ages trying to look up the table that deciphers all the codes & gave up. I'm sure it's here somewhere (at least, it used to be!), but I can't find it now.

securespark · 1 Oct 2012

Perhaps the "not lighter than" refers to the temp. rating of the cable?

ban-all-sheds · 2 Oct 2012

securespark said:
I'm sure it's here somewhere (at least, it used to be!), but I can't find it now.

//www.diynot.com/wiki/electrics:harcode

securespark · 2 Oct 2012

Has that changed recently?

I spent ages trying to find it the other night...maybe I was tired!

H=Harmonised

05=300/500V

R= Rubber conductor insulation

R= Rubber sheath

V= PVC conductor insulation

V= PVC sheath

F= Finewire Flexible

So, either rubber or PVC insulated flexible cable, but no hint as to the CSA, as Peet said.

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Replacing flex on a Bosch built-in oven

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