New RCD needed - probable cost.

[Silvan]

Hi,

I am thinking to change my cooker from gas to electric. The house is 45yrs old. I messaged a local electrician asking him for advice and he reckons from what I have said in my messages and the picture I sent him that I might need to do something with an RCD.

As far as I know all the sockets except the cooker socket are on the RCD in the picture. The cooker socket is on the pull-out fuse. The other pull-out fuses are no longer in use. The reason for this is that we had a conservatory built and it as part of that the electrics needed upgraded and the RCD was fitted. But the cooker socket was not in use at the time so maybe they ignored it?

Electrician is local he thinks 6mm wire will be present. I am looking at a ceramic cooker of 6.7KW max (all four rings on at the same time). We don't have an oven so no power requirement there.

What might be required and what might it cost?

David

 

[ericmark]

There is no law to say you must use an RCD, but to follow regulations (they are not law) any new circuit will need RCD protection, and a scheme member electricians sign a contract with their scheme providers to say they will follow regulations, so contract law forces them to comply.

Since a cooker is hard-wired, it does not really need the RCD protection we feel is required for sockets, so it would not really worry me too much for it not to have RCD protection, and I am sure you could find an electrician who will connect up the new cooker. But I can also see why some would refuse.

 

[Silvan]

Electrician has just been. All the sockets are on one RCD. Lights, immersion heater and cooker socket on fuses. He would have been happy to wire up the cooker to the fuse. But because there is a spare unused thingy on the existing RCD box he says he can add an extra RCD to the box and route the cooker socket through it, the additional cost being around £10. Waiting for his quote but I think it will be £80 ish to wire the cooker and add the RCD.

 

[Murdochcat]

Don’t waste your money on a stand alone RCD - but put the money towards replacing the old CU for one with RCBOs

 

[Silvan]

The extra RCD only adds a tenner or so to the cost of the visit to fit the cooker. The electricians visit to investigate was free. He did mention that the whole thing with the old fuses could be replaced with RCDs but that would cost around £500.

 

[ericmark]

How far you go is up to you. In the 90s my son became a radio ham at 14, and I decided all should be RCD protected to protect him. My dad didn't and as a boy I did get some nasty belts, clearly didn't kill me, but to what extent one raps people in cotton wool is down to you.

I would say sockets are a must, specially with some of the rubbish on the market today, I have seen wallmarts fall apart as withdrawn from the socket, but I have a far amount which I bought when working in Hong Kong.

So my distribution unit is now all RCBO so that the likely failure of a critical circuit is also reduced. £500 sounds a lot, but how much to restock a freezer if a single RCD fails, when it happened to me, there were no freezers on that supply, so could wait until morning to sort. Chest freezers will keep stuff for 24 hours, but upright it depends on when it did the last defrost cycle, you may have less than an hour.

But someone who does no DIY, and buys all electrical goods from high street stores should be reasonably safe, but using Temu or Amazon, you can't rely on their buying department keeping you safe, and once you start drilling holes in the wall, also you may be exposed to danger, also I know we have the odd mouse, which was simply not fast enough, and out cats have caught them and brought them in, then released so they can practice hunting skills in the warmth of the house, that's the problem in having a cat flap, and if they fail to catch them, they may eat cables.

 

[Risteard]

RCCB for £10? £80 all in?

That's no Electrician. Even a handyman would be dearer. And no-one can find an RCCB for a tenner.

 

[JohnD]

And no-one can find an RCCB for a tenner.

Out of a skip?

I've repurposed a few used parts subject to age and condition, but I had the advantage of a good tester.

 

[Silvan]

He had a look at the RCD box in the picture below. He took the cover right off and it was kind of modular in there. To the left of the switches there was a vacant area, I think he is going to slot something in there. So when it is done I am supposing that right under where it says NHRS-204 there will be another RCD switch. Does any of this make more sense now? I asked him for a proper quote, will wait and see what it includes and how much he wants.

(sorry the image spins itself around when it uploads to diynot. In reality the old fuses are above the RCD box).

 

[JohnD]

Is the entire old MEM consumer unit out of use apart from the sockets and cooker? It was good quality 40 years ago but is overdue for replacement.

Are there any spare slots in the new CU you mentioned? Can you provide some pics?

 

[JohnD]

He had a look at the RCD box in the picture below. He took the cover right off and it was kind of modular in there. To the left of the switches there was a vacant area, I think he is going to slot something in there. So when it is done I am supposing that right under where it says NHRS-204 there will be another RCD switch. Does any of this make more sense now? I asked him for a proper quote, will wait and see what it includes and how much he wants.

(sorry the image spins itself around when it uploads to diynot. In reality the old fuses are above the RCD box).

I have a feeling he may add another MCB on the existing RCD. That would be inexpensive.

 

[davelx]

My guess is that the electrician is proposing to add an extra (32A) MCB (not RCD or RCCB) to the existing RCD protected CU, which would indeed be about a tenner.

 

[Silvan]

Yes that sounds like it. Sorry I have been using terms that I don't understand. From a users point of view the idea is that if the cooker circuit blows something it won't be the fuse (which is near impossible to get out and hard to fix), it will just trip out a little switch which can be flipped back (after switching everything off and hopefully figuring out what caused the problem).

He did say that he was obliged to suggest that I get a big fix which involved removing the fuse board altogether and replacing it, but that would cost £400 or more.

The new hob will be 6.5KW and also on the circuit are a washing machine and a dishwasher. If they were all on full power (i.e. all four hob rings and and both the dishwasher and the washing machine heating water) might that overload? (there is no oven).

Is the idea of adding a 32A MCB a good reasonable one?

 

[ericmark]

Should give you an idea what they look like and cost, I went for around the cheapest I could find.

Again the whole unit, with surge protection and isolator. In the main, an electrician wants to charge by the ½ day, it takes time to move from job to job, and with a consumer unit charge to worry is always finding something missed with the inspection, like a borrowed neutral on stairs lighting.

It takes time to explain pros and cons of having a split RCD and all RCBO board, So I will try point one is with RCDs the box is 4 modules wider, and around £25 cheaper. But a fault takes out half of the house. Also, if the ring final and lighting are not split the same, need at least one RCBO anyway. As if someone gets a shock, you don't also want them plunged into darkness.

The more circuits we have, the less we loose with any single fault, a circuit is defined as "An assembly of electrical equipment supplied from the same origin and protected against overcurrent by the same protective device(s)." in my old book, it does not say overcurrent where, if line to neutral or lives to earth, so with two RCDs we are just splitting the house to two circuits. But with 6 RCBOs then 6 circuits. But these definitions could be read differently.

So we have two arguments, one what the regulations say, which one can debate until the cows come home, and what is the best for the occupier, and for £25 seem better to have all RCBOs.

 

[flameport]

Is the idea of adding a 32A MCB a good reasonable one?

It's an option which is better than the alternative of shoving it onto one of those old rewireable fuses.