I have a Wylex Consumer unit with rewireable fuses. The cooker fuse is
30A (Red) which I need to change to 15A (Blue). Do I have to change the backplate as well as the fuse, as the cable is still rated at 30A so the 30A fuse could safely be reinstated for a future appliance (6mm cable). I just want to fuse the current cooker with a lower value as it has a gas hob. So the question is - is putting a 15A fuse in a 30A fuseway against any regs?Thanks
John
It would be much neater and safer to fit a 15A backplate (or a 16A MCB) to avoid any confusion at a later date.
Not against regs .. .if you want to use a lower A fuse holder then you would need to change the plastic back plate. So rewire with fusewire you want and save the money - you can always attach a label to advise.
The 15A fuse former[1] (blue dots) won't fit the 30A backplate - so to actually change it would require you change the back bit as well (they usually come as a set anyway - but it does mean playing near exposed live parts since you will need to take the front off the CU to change it).
You could however just label it carefully and use a lower rating of fuse wire.
[1] I am assuming you really mean rewireable holders rather than cartridge fuse holders. If the latter then the fuses are different sizes and won't fit the wrong carrier.
You don't actually need to take the front off the CU - all you do is (carefully) remove the single fixing screw for the backplate and lift it out. Refitting is the reverse of the above - but be careful as the busbar behind is live and it's easy to catch the screw on it.
Thanks - that is what I will do. It will also make me get a card of fuse wire for my daughter's house as I threw mine away 20 years ago when I moved and got a cartridge fuse consumer unit. You never know when you will need it.
Interestingly, the cooker has two ovens with ratings of 2.4/2.7 Kw and 1.8/2.0 Kw at 230/240 V and specifies 4mm cable for connection. It then specifies it should be fused at 13A, which seems a bit light to me!
John
So play safe and switch off the main switch while working on it.
Yup, I think you are right if you don't need access to the circuit wires...
If in doubt, turn off the main switch - then the only live bit is still under cover (unless you are right up against the switch end, where if memory serves, you may be able to poke something into the metalwork near the top of the switch).
You normally apply diversity to the calculation for a domestic cooker. This is 10A + 30% of the remainder of the total load (assuming no socket on the cooker point - add a further 5A for a socket).
So in your case the total load is 4.2kW or 18.26A So that gives you 10A + (18.26 - 10) * 0.3 = 12.48A
You can get away with this because the load is thermostatically controlled, so once the element is up to temperature the stat will be cycling the power, thus giving a lower overall average. The instantaneous peak current is less important since it takes time to heat a cable to a point where it would be damaged, and so its temperature will tend to reflect the average load on it rather than the peak.
It would be confusing since the colours wouldn't be the same.
But unless I'm missing something it's not a backplate and merely a cover held on by one screw - and can be changed in seconds.
Thanks - that is what I will do. It will also make me get a card of fuse wire for my daughter's house as I threw mine away 20 years ago when I moved and got a cartridge fuse consumer unit. You never know when you will need it.
Interestingly, the cooker has two ovens with ratings of 2.4/2.7 Kw and 1.8/2.0 Kw at 230/240 V and specifies 4mm cable for connection. It then specifies it should be fused at 13A, which seems a bit light to me!
John
If the specification is for 13A then swap the cooker outlet plate if you have one for a switched fused spur with a 13A fuse and leave the Wylex fuse at 30A.
What make and model is the cooker? Asking for 4mm connection cable sounds a little like overkill.
Adam
Too true, and to make it worse the screw is closer to the busbar than it is to the outgoing "dead" terminal at the top. Add the massive amount of play in the screw and it is easy to get caught out.
Adam
What do you really think the consumer unit fuse / MCB is protecting? It's almost never ever the appliance, it's the cable.
Leave the 30A fuse in there with the existing cable and even if you installed a cooker with no heating elements and just a 15W light in the oven space then your installation is safe and adequately protected.
Interesting point, and with the common practice of populating CUs starting with the highest rated fuseways closest to the main switch that could be quite likely in this case.
That sounds about as safe as letting Gary Glitter babysit the kids with Micheal Jackson supplying the entertainment and Beverley Allitt acting as the nursemaid with Sharon Shoesmith overseeing it all in case things go wrong.
Adam
In article , John Rumm writes
It's dark out and I'm not about to start farting about with my fusebox, but I seem to remember that lower-rated fuses will fit the higher-rated backplates (so you could put a 5A fuse into a 15A backplate for example) but not vice versa.
Actually, I've just had a play with my stock of Wylex rewirable spares. There seem to be two different types of backplate - recessed and flush. A 5A fuse will plug into a recessed 30A backplate, but not a flush 30A backplate.
But it is completely safe. Do you suddenly decide to fit a smaller MCB or fuse on a ring main when because of the credit crunch you stop using a 3 bar electric fire to keep warm and sit instead round a 15W candle lamp plugged into a 13A socket outlet for warmth?
The plug fuse protects the cable to the lamp, the fuse or MCB at the consumer unit protects the fixed wiring.
A 30A fuse or MCB fitted in a consumer unit, on a circuit such as a cooker circuit using cable originally sized for carrying that load is safe with a load of 30A (and beyond) or without any load or with any load between those values.
What if you fit a gas cooker and for some ambient lighting in the kitchen you plug a able lamp into the socket on the cooker outlet unit. Does that installation, fuse/MCB cable etc suddenly become unsafe? (assume the lampshade is nowhere near the gas flame!)
For f*cks sake calling someone to back me up on this! Am I right or am I completely mad?
Are you sure, John? I thought the only difference apart from the colour was the size of the holes for the fuse carrier pins - so a 'smaller' carrier would fit, but not a larger one.
What's that to do with 'credit crunch'?
Is that a sort of breakfast cereal?
I think we're all (fsvo) mad.
It is a Hotpoint EG74 Dual Fuel. I did assume when it asked for 4mm it would be fused at 30 A, but the book says 13 A.
John
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