Wylex Fusebox - Replacing fuses with plug in MCBs is a waste of money

Wylex fuseboxes with rewireable or cartridge fuses are very common in older properties. Plug in MCBs can be obtained for these, and are simple to install.

However doing so is a waste of money, since the MCB does not offer any additional protection compared with a fuse.
Both devices disconnect the power in the event of an overload or short circuit.

The only advantage of the MCB is that is is quicker to reset - but fuses should fail almost never, and if fuses require replacement often, there is some other problem which no replacement device will fix.

New consumer units will contain one or more RCDs, which will disconnect the power in the event of an earth fault, such as someone touching a live wire.
It is impossible to fit these into old fuseboxes like this.

It would be possible to add an RCD separately before such a fusebox, and there are some installations where this has been done. However adding an RCD in this way does not comply with BS7671, as in the event of a fault on any of the circuits, the entire installation will be disconnected and will remain that way until the fault is located and repaired.

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[alvinashman]

Not only are the circuit breakers more convenient in terms of reinstating power, it's makes identifying which circuit has tripped far easier. If your fuses are blowing all the time, it's probably best to get an electrical safety check done on your house.

[timsteele]

I can think of three reasons why you might want to fit the MCBs, as I did to my Wylex consumer unit many years ago. It's cheaper than replacing the consumer unit, , you don't need an electrician, and it makes it easy to turn off individual circuits before replacing light bulbs, for example.

[HILUXCHAINSAW]

If the fuse goes it's a pain in the ass to fiddle around with the wire especially if it's the lighting that's blow....and it's night. You also hear about people using bits of metal instead of wire. For these 2 reasons alone I would change to MCB's .

[poorboymechanic]

Superb. Just what I wanted to know. Short sharp & to the point video inclusive of relevant safety points. Well done you & thanks for sharing. This type of information actually saves lives. Much appreciated !!!!

[tjpj]

For such a cheap upgrade it’s definitely worth it. When a bulb blows and burns out the fuse wire, my elderly parents can restore power by themselves. That alone is a good enough reason

[tmerlin]

I have only had to re - thread a fuse wire once. doing it the dark, holding a torch in my mouth convinced me that pressing a reset button once in 14 years is worth it, even though apart from convenience, there is no value - add in replacing them

[llynellyn]

The plug in MCBs may not offer much additional protection but they are 10, 000x more user friendly. Worth every penny.

[TheHairyHound]

BRILLIANT video. Thank you John.
Clear information which has just saved me ???£'s. I was mind set on replacing my old fuses with trip switches thinking the trip switch would save anyone (by that I really mean me) being electrocuted if they did touch a live wire.

[septimus]

When the fuse-wire blows, it's not usually a fault with the installation, but an old style incandescent lamp blowing (or a tungsten halogen equivalent). My father who is 85 now has found the replacement MCB very useful, especially as he has only one good arm after a stroke, and replacing the fusewire is fiddly for him. The other point to mention here is the price of LED equivalents which are not yet up to the brightness of old 100W lamps with the same colour temperature, ie 2700K. have a noticeable reduction in light output with time. I have tested the reduction in light output on LED lamps, especially those with SMD's, and a drop of as much as 25% happens within just a year. If 6000K lamps are used, the blue light reduces the production of melatonin, causing people difficulties getting off to sleep, or insomnia. I say bring back the old incandescent lamos!

[Mattja]

Probably the greatest advantage with an MCB is that when a fuse blows then someone who has no idea what they're doing may replace it with too large a fuse or something else entirely (in some cases a nail or strip of copper!), and then the circuit is no longer protected, but an MCB is a bit more fool-proof.

[gbelectricks]

I recently upgraded some BS3036 rewireable fuses, as the external Earth fault loop impedance (Ze) was extremely low. This in turn gave a very high prospective fault current, somewhere in the region of 2.5kA. The old rewireable fuses were only rated (S1A) or 1kA. The newer plug in mcb’s (to BSEN60898) are rated to 3kA. Hence the reason for the upgrade. I suggested a consumer unit upgrade as a first option however, the cost was an issue so this upgrade was the cheaper option. I would agree with some of the comments that an MCB is more user friendly, for instance, in the case of an elderly customer who’s is trying to rewire a blown fuse holder in the dark. 🔦

[dead.format]

indeed you may as well upgrade the whole CU for what it's worth, but for a few quid they are more sensitive, and also prevent any abuse with incorrect fuse wire being fitted etc...

[MacMcCaskill]

Very helpful and easy for a non-technical layman to understand. Clear information and advice. 👍🔌⚡

[Graham_Langley]

These MCBs do have a use on lighting circuits, were a cheap GLS lamp with no internal fuse can take out the CU fuse when it fails.

Also the non-combustible CU reg change isn't retrospective.

[mechrojo]

Thanks for sharing your information. You present it in a easy to understand way. Following from Sydney Australia

[RobertSzasz]

The MCB also has the advantage of being able to be shut off without exposing line voltage.

[geoffbryant]

You havn't mentioned 'Fusing Factor'. A BS3036 rewireable fuse has a fusing factor of '2' which means that it will carry twice the rated current for up to 4hours before disconnecting. A circuit breaker has a fusing factor of 1.45 and will therefore disconnect at a lower overload current. Because of this the 17th Edition Regs applies a fusing factor where BS3036 fuses are used which means essentially that a larger cable size has to be used when BS3036 fuses are used. Other benefits of using circuit breakers is that they have fixed values of tripping current and cannot be meddled with as with the fuse ie.incorrect fuse wire being used. There are other benefits to using circuit breakers and in short I would recommend their use.

[avtardisange]

Thank you so much for this video, i have have fuse box, like this in my house, mine is cream, i have had no problems at all. Was thinking of getting those MCBs however if it is not broke, do not fix it. I do not overload, and no fuse has ever gone. All these new regs, are all there to take If the old ones are bad, how come they lasted so long. Look at Grenfell tower, if that had just been left alone, without the cladding, just a concrete structure, it would not have happened, and the Boeing Air Max once again, the new one, they could have stuck with the old model, and they had serious problems, The Russians, never bought the latest, models of airmax, they stuck with the one before, cost a fortune.

These work, and they are safe, and i have had no problems at all, So many times, i have seen the latest cause problems, or cause different problems. I was at a church recently, and the preacher was telling everyone that his Electrics kept tripping, the Electrician spent a whole day looking where the fault was, he could not find it, and may need a rewiring. It was difficult without light. The same thing happened at our Table Tennis Club, it kept tripping, they think it was the refrigerator door. It had to be rewired, and new sockets put in. It had been fine for many years, no problems. You have to be careful. I read on the internet,

Wiring PVC the copper can last upto 100 years, and the grey sheath covering, can last, up to 50 to 70 years, it all depends on usage rather than a clock, it it has been changed, constantly tampered with, overloaded, it will not last that long. So this box, andi like they way has explained it in a fair way is still useful under the right conditions. There will be some Electricians, who will mention it is dangerous, fire hazard, need to up dated, illegal, is too old.

The suckers among us will soak it up, and get frightened, and pay out a lot of money, when it did not need to be done. If it is that bad, how come i have no problems with it in 30 years, no nothing, that is the evidence, i like this video, and it explains that, Well done, your a star, helping the public, forget the MCBS they might not be better in this case, Thank you so much, as worried about this subject.

[kevvywevvywoo]

My Wylex is a wooden one like that and that's the way it's staying. I retrofitted the latest MCBs (its a 4 way) and an outboard whole house RCD. There's no way I could get anything else in the meter cupboard as it's an outdoor one with meter, bell transformer and garage isolator. Full! MCBs are also classed as 'close circuit protection' which is no doubt renamed something less informative these days, and allow greater tolerances on circuit diversity, cable capacity and impedances than rewireables. There used to be tables of capacities in the IEE regulations for rewireable vs HRC/MCB protection, though I think the trend for over-complicating and obfuscating the rules has meant we now have confusing derating factors under the present IET tenure as electrical God.

[pachma]

Lol. "It's a waste of time spending £40 on circuit breakers to replace the old fuse wire units".
Much easier to spend ten times that on an electrician to install a new consumer unit.