Replacing Fuse wire with MCBs

dave-lew99 · 14 May 2009

Hi all,

I'm just about to move into a new house and i've noticed that it has good old fashioned fuse wire on an old Wylex consumer unit.

Now, i'm only renting the place so there's no point in having it re-wired etc, but personally, i do a lot of IT/Electronics work (so i have a lot of kit running and often have live (low voltage) electronics open on my workbench).

Because of that i'd be happier with MCBs (my workbench is going to have one of those plug-in RCDs)

I've noticed that just simple swap-plug-in MCBs for my consumer unit are about £7-10, if i buy the 4 required and just plug them in (doesn't require opening the unit) is that okay in terms of regulations etc? Obviously i'd have to make sure they're the correct rating.

When i move out i can just swap the fuses holders back in, it'd be about a 30 second job really.

bernardgreen · 14 May 2009

Check with the landlord before you do it.

And what would Part P building regulations have to say on the change ?

rebuke · 14 May 2009

It would be notifiable under Part P, as you're changing the protective device. Having said that, I suspect if I were in a similar situation personally I might be tempted to just pop them in...

dave-lew99 · 14 May 2009

See that's the thing, taking those rules literally, i'd need a qualified electrician to change the fuse wire!

How far are we from having to call someone in to reset a breaker? hehe

Since they're literally just plug in/swap jobs - no wiring required i will probably just do it.

I seriously doubt this property is up to code anyway - they did a load of re-wiring downstairs for the new kitchen in the last couple of months and they've put the electric oven on the downstairs ring main...

rebuke · 14 May 2009

Well, I should have said changing the type of the protective device, replacing fuse wire, or even an MCB with one of the same type would not be notifiable, as that's considered maintenance or similar.

dave2506 · 14 May 2009

If that is indeed the case I would be calling the landlord rather sharply for fear of the 2.5mm cable melting. Unless of course it is a very low power oven...

dave-lew99 · 14 May 2009

I don't know yet, i'll be making lots of checks when i move in properly.

(i've also bothered to search the forums for other people doing that i've proposed) It seems that i really shouldn't but it's a simple/safe job to do anyway.

My estate agent has a contractor in (hopefully today) to fix the stuff the builders didn't - two of the lights plain don't work and get this - they 'forgot' to put in a waste pipe connection for the washing machine! (after putting in water inlet and power connections to the new utility room)

Anyway, he might spot something while he's playing with the lights. I'm pretty sure they've run new cable for the downstairs though - the fuse marked 'spare' seems to be connected to the cooker and sockets.

Each pair of sockets also has it's own fused switch (13A) and IIRC, the cooker is also on a 13A fused switch. Hmm, need to investigate further methinks...

rebuke · 14 May 2009

If it's just an oven, it's conceivable it could use 13A, you quite often get 3kW ovens. Normally though you wouldn't run them on the ring main, as 13A is quite a sizeable chunk, especially from a kitchen ring that will have other appliances on. In my house for example, it is a 3kW oven, run from an FCU hooked up to a dedicated cooker circuit (which also feeds the electric hob).

dave-lew99 · 14 May 2009

Personally i was under the impression it was mandated that it had to be on a seperate circuit (but i'm not an electrician)

It's brand new, high efficiency (A or B rating i think, single fan oven), it's likely to be fairly lowish power and a gas hob. So i'll be checking the specs but it's probably okay.

I might run into problems if i have the kettle, oven and washing machine on at the same time though. Not to mention i had planned to leave my server rack downstairs too. (Although thats only about 600w really when running normally).

As i said, i'll be testing and documenting the system fully, to make sure it's safe.

ban-all-sheds · 14 May 2009

dave-lew99 said:
Now, i'm only renting the place so there's no point in having it re-wired etc, but personally, i do a lot of IT/Electronics work (so i have a lot of kit running and often have live (low voltage) electronics open on my workbench).

I'm sure you're careful with that - 50V - 1000V AC between conductors or 50 - 600V AC between conductors and earth can bite quite badly...

//www.diynot.com/wiki/electrics:voltage-bands

if i buy the 4 required and just plug them in (doesn't require opening the unit) is that okay in terms of regulations etc?

It's notifiable....

ban-all-sheds · 14 May 2009

dave-lew99 said:
See that's the thing, taking those rules literally, i'd need a qualified electrician to change the fuse wire!

No you wouldn't - that's quite clearly non-notifiable.

rebuke said:
Well, I should have said changing the type of the protective device, replacing fuse wire, or even an MCB with one of the same type would not be notifiable, as that's considered maintenance or similar.

Changing the type of protective device is notifiable.

dave-lew99 · 14 May 2009

ban-all-sheds said:
I'm sure you're careful with that - 50V - 1000V AC between conductors or 50 - 600V AC between conductors and earth can bite quite badly...

Hehe, sorry, i come from an electronics background - what i call really 'high voltage' is 50V-240V

I really meant extra low voltage in electrical definitions, most i tend to deal with is +/- 18V AC out of a transformer - i'd never plug anything in with exposed 230v.

rebuke · 14 May 2009

ban-all-sheds said:
rebuke said:

Well, I should have said changing the type of the protective device, replacing fuse wire, or even an MCB with one of the same type would not be notifiable, as that's considered maintenance or similar.

Click to expand...

Changing the type of protective device is notifiable.

That's what I meant, re-reading it I can see it doesn't make that clear due to some ambiguous grammar

ban-all-sheds · 14 May 2009

OTOH...

I've been looking at this from the POV of replacing a CU.

Given that Schedule 2B says this:

1. Work consisting of—
(a) replacing any fixed electrical equipment which does not include the provision of—
(i) any new fixed cabling; or
(ii) a consumer unit;

replacing a plug-in rewirable fuse carrier (fixed electrical equipment) with a plug-in MCB, but not replacing the CU, should be non-notifiable.

Not that the Building Regulations define what is meant by "fixed electrical equipment"...

sm1thson · 14 May 2009

dave-lew99 said:
they did a load of re-wiring downstairs for the new kitchen in the last couple of months

is the new wiring RCD protected? what exactly have they altered?

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Replacing Fuse wire with MCBs

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