Connecting two ovens

[Sparks]

I currenly have a 6mm cable running from a 32A MCB in my CU to where my ovens are going to be put.

The two ovens are rated at 3500w and 3600w.

I want to use the same 6mm feed for both.

Do need to install a fuse at the oven, nearer to the ovens rating (Say 16A) If so, where do I get such a fuse, as a normal FCU only goes up to 13A.

Personally, I would want to install a fuse, so if the oven tries to draw too much for any rason,the fuse/MCB whatever, will blow.trip, but do I actually need to do this!?

The old ovens we had was a double oven, and a steam oven, the steam oven was only rated at about 800w or so, and this had been connected via 2.5mm to the isolator (connected to a 32A MCB in the CU)

Also, what size cable do I need to use between the oven and the isolator? Would 2.5mm be ok, as this is a short run (about 1m) or do I need to use 4 or 6mm?

Ta!

Sparks...

[Christian McArdle]

This will depend on the oven. I would suspect that most UK specific ovens over 3kW will be OK at 32A. However, an oven in the 3kW to 3.7kW range might be a European model designed for 16A and not expecting a 32A circuit. This is because the UK commonly uses 32A circuits where the Europeans would expect multiple 16A ones.

You basically need to see what the installation instructions say. If you can't find any, or they stipulate 16A or 20A protection, then you need to do one of two things:

1. Run an additional circuit from the MCB (presumably you're trying to avoid this).
2. Install a "local" consumer unit at the end of the 6mm cable (preferably hidden in a cupboard or suchlike) with 2 16A MCBs. From there, 2.5mm cable can be run to the ovens.

With a 25A fusing requirement, you might get away with it using diversity, although I'm not entirely sure you are allowed to use it for two ovens, rather than one oven and hob.

2.5mm will normally be fine, even using a 32A MCB only. However, it must be short and you should really calculate that the earth loop impedence will allow immediate disconnection of the MCB. When using the 16A MCBs, the 2.5mm can afford to be much longer, as the maximum allowed earth loop impedence will be double.

Christian.

[Sparks]

OK, the combination Microwave oven is a Siemens HB86K.70B The Installation instructions only say "Great Britan and Australia This appliance is designed for permanant connection to a 3-wire cable. This appliance must only be connected by a qualified electrician in accordance with the wiring diagram attached to the connecting cable"

This "Wiring diagram" is simply some wording, explaing what colour cable is what, and also stating "A plug must have a nominal current of at least 15 ampere or more"

So no mention of any fusing requirements there!

The normal oven hasn't got a cable, but does have a beefy looking cable clamp.

Sparks...

[Christian McArdle]

Without further information, I'd have to go for one of the 16A options. Either a local consumer unit with 2 16A MCBs or an additional circuit back to the main CU.

Alternatively, you could contact the manufacturer's technical department.

Christian.

[Sparks]

Well Siemens were pretty useless really

"All I can advise is the current rating of the appliances. The fuse rating should be the next size up. For the HB86K70B is a 3.6KW appliance which takes 16amps For the HB76L550B is a 3.5KW appliance which takes 16 amps"

Looks like a small 2 way CU un the cupboard above then (Not really what I wanted to do!!)

Sparks...