16.5kw Electric Cooker, What size Breaker? Pictures added

[JohnW2]

We will be getting a brand new consumer unit john, we would never keep that old thing. Yes the earth is staked outside, but we are running 2 10mm earth cables in for that.

Ah - OK.

That VO-ELCB (assuming that's what it is!) needs to go. If you still need an RCD there (see below) it could be replaced with that. Otherwise it could be replaced with an isolator (to make life easier for, say, the electrician who replaces the CU).

With the earth rod, you have a 'TT' installation. That means that every circuit in your installation needs RCD (or RCBO) protection. If the new CU is going to provide such protection to all circuits, then you don't need another RCD where that VO-ELCB is (so it could be replaced with an isolator). However, if there is going to be so much as one circuit that does not have RCD/RCBO protection, then you would have to have the VO-ELCB replaced with a ('time delayed', probably 100mA) RCD.

Kind Regards, John

 

[JohnW2]

That old voltage-operated earth leakage circuit breaker will definitely do duty as an isolator. But you'll only need an isolator once the CU is replaced, so if Npower are going to fit a new one for free, then go for it - you don't want the old breaker going wrong.

Not only that, but nor do you really want the (possibly ~500&#937 VO-ELCB coil unnecessarily stuck in the earth path.

Kind Regards, John

 

[Barney1686]

Yes he said it would be installed where the current one is.

The 21 way is a MK 21 usable way, that's all he told me, though he is coming back to talk about the design of the circuit again.

 

[Barney1686]

Just to clarify, he wants a isolator switch fitted before he will work on it as he said he could not switch off the power safely.

 

[JohnW2]

Just to clarify, he wants a isolator switch fitted before he will work on it as he said he could not switch off the power safely.

That makes sense - although, as BAS said, as a temporary measure, he could probably use the existing VO-ELCB to switch off the power to the CU.

However, remember what I recently said - whether you need to replace that thing with an isolator or time-delayed RCD (or, I suppose, both) depends upon whether the new CU will give RCD/RCBO protection to all of the circuits in the house. On the other hand, putting an isolator there would be OK either way, since a T-D RCD could be subsequently added (switching off power with the isolator to install it), in addition to the isolator, if required.

Kind Regards, John

 

[JohnW2]

The 21 way is a MK 21 usable way, that's all he told me, though he is coming back to talk about the design of the circuit again.

If he really means 21 usable ways (i.e. spaces for 21 MCBs/RCBOs), that's an awful lot for the average house! Is he sure there will be enough physical space for it?

Kind Regards, John

 

[Barney1686]

Ok John, gotcha

He said all circuits will be protected on a RCD, existing and new.
As for space it has a big wall to go on but I cannot see where we will use them all, I think he said you have to leave space for upgrades?
Thanks again for your help btw

 

[JohnW2]

Ok John, gotcha ... He said all circuits will be protected on a RCD, existing and new.

OK. As I said, if that's true, then the VO-ELCB could just be replaced with an isolator.

As for space it has a big wall to go on but I cannot see where we will use them all, I think he said you have to leave space for upgrades? Thanks again for your help btw

You're welcome. I have to wonder about this '21 usable ways' CU. Assuming two RCDs and a main switch, each requiring 2 'ways', that would amount to 27 'ways' in total - which is an awfully big CU! A small number of 'spare ways' is always nice to have, but this could be a bit OTT!

Kind Regards, John

 

[ban-all-sheds]

The 21 way is a MK 21 usable way, that's all he told me.

It's not.

MK count all of the positions.

Here's a photo of a 21-way MK CU:

From L-R

2 Main Switch
1 RCBO
2 Unused
2 RCD
7 MCBs
2 Unused
2 RCD
3 MCBs
--
21

 

[Barney1686]

Just going by what he told me and wrote down Ban all Sheds.

He showed me a picture of an empty one, ( he says he buys just the case )he then buys the relevant Rcd's and what not, he said it will cost £174.

Again this is just what he told me he wanted to do, I will ask for more and better details next time we meet.

Thanks for the pictures and help.

 

[ban-all-sheds]

Just going by what he told me and wrote down Ban all Sheds.

He showed me a picture of an empty one, ( he says he buys just the case )he then buys the relevant Rcd's and what not,

OK - it's just a mis-match of terms.

An empty case will have 21 "useable" ways. But some will be used by the main switch and the RCDs. 1 main switch and 2 RCDs will use up 6 of the 21.

he said it will cost £174.

I'm sure he can get a better deal than that by buying a populated one, even if he has to swap a few parts.

 

[Barney1686]

Thanks for the info, he said it is at cost so will ask him exactly what will be in it and I will do the math, cheers.

 

[JohnW2]

Thanks for the info, he said it is at cost so will ask him exactly what will be in it and I will do the math, cheers.

As BAS has said, I'm sure that he would be able to find one with a main switch, two RCDs and 15 MCBs for appreciably less than the cost of buying those components separately, and that includes the case 'for free'. It could be different if he is thinking of using RCBOs, so you need to quiz him about the proposed details!

Kind Regards, John

 

[ban-all-sheds]

I guess with an external isolator and RCBOs you would have the full 21 useable ways....

 

[Barney1686]

Yep I asked him about RCBO and he said nope just RCD, which to be honest for £174 I was a tad disappointed.