Please Advise On Kitchen Rewire

[FirstTmeBuyer]

Hi I've been reading here for a few months and for my first post I was hoping someone could double check that I'm on the right track with my kitchen rewiring plan. First off I know it's part p and notice has been given to building control.

My house seems to have had a recent rewire and I have a new looking mem 2000AD CU.

1. HOB WIRING
I have a 6400w rated hob and there is already a cooker point wired with 4mm cable on a 32A breaker. I would like to reroute this cable without changing the length or extending it to run the hob and hob alone. Do I run the cable into an isolating switch 1st and then run some more 4mm to a hardwired cooker outlet? Is this all sufficient and in line with regs? User guide says 2.5mm and 25A so I presume this is ok for now but may not be adequate for an upgraded hob?

2. IMMERSION OUT BOILER IN
I have removed an old back boiler and am having a combi condensing boiler fitted. The old immersion (which has since taken a trip the scrap yard) was connected to a 16A breaker on 2.5mm cable. I would like to reroute this cable to run just the boiler. Do I just wire the 2.5mm into a 3A FCU and leave the 16A breaker? Is there any particular reason or benefit to having it on it's own circuit.

3. KITCHEN RADIAL TO RING
I currently have just 2 double sockets in the kitchen each 1 a radial from a 16A breaker. Because both cables run from the same point on the CU I would like to add more sockets inbetween ultimately turning this into a ring. I would like to add 1 more double, 1 single, an isolating switch for a 2400w single oven and 1 more single or an FCU for a cooker hood. I know the breaker will have to be changed to a 32A. Should I run the hood from a single socket with a plug or an FCU? Do I have to have another isolating switch for the cooker aswell as the hob or can they be wired into 1 dual switch and then independantly to the oven and hob using the 2.5mm and 4mm respectively?

4. CHASING IN KITCHEN
I'm going to have to chase cables in all sections of the wall mid, corners, up near the ceiling for cooker hood. Can I run these in conduit or do they have to be protected with metal? Can anyone provide a link to show me what I need to be looking for along the lines of metal mechanical protection if that is whats required as I can only seem to find armoured cable. Does the metal protection have to be earthed?

5. EXTEND LIGHT CABLE
Is it ok to extend a 1.5mm light switch cable using a junction box or should I run a fresh length. Would be much easier to extend. What AMP junction box should I be looking at for this cable. Is 16A ok?


Sorry if that's a lot to take in. Thought I'd get it all out in 1 go.

 

[FirstTmeBuyer]

Anyone?

 

[Dippy]

OK, I'll have a go. I don't have any books with me so this is from memory.

1) If you want to reposition the hob without completely rewiring, then yes you need to insert a junction and a suitable switch will suffice. Check the regs on max cable length (is it 30m?). Have you already checked continuity/loop impedance to make sure it's currently low enough to be able to add more cable?

2) I think the point of the 16A breaker is that this is a radial and a water heater uses quite a lot of current. You'll only need to add an FCU if the wiring to the boiler is not rated for 16A which I suspect it is not. The alternative could be to change out the 16A breaker to a lower rated one, but leave a lable on the CU explaining why.

3) I'm confused about this as you are referring to creating a ring in the kitchen and wiring in the cooker in the same sentence. I'm not too familiar with cooker circuits but isn't the whole point that they take up so much current (10A) to need their own circuit. As for using a socket or FSC for the hood I think that's a matter of choice. I don't think there are any regs covering it. Personally I like having an FCU for fixed equipment, but I can't say I can really justify it.

4) BS7671 doesn't require any cable protection as long as the cable routes follow the guidelines (basically vertically or horizontally from points).

5) Yes as long as the box is accessible for inspection (and the total cable length and loop impedance does not exceed the max for your installation).

 

[Chri5]

1. HOB WIRING
I have a 6400w rated hob and there is already a cooker point wired with 4mm cable on a 32A breaker. I would like to reroute this cable without changing the length or extending it to run the hob and hob alone. Do I run the cable into an isolating switch 1st and then run some more 4mm to a hardwired cooker outlet? Is this all sufficient and in line with regs? User guide says 2.5mm and 25A so I presume this is ok for now but may not be adequate for an upgraded hob?

32 a x 230v = 7kw 'ish. Isolate with 40a switch

2. IMMERSION OUT BOILER IN
I have removed an old back boiler and am having a combi condensing boiler fitted. The old immersion (which has since taken a trip the scrap yard) was connected to a 16A breaker on 2.5mm cable. I would like to reroute this cable to run just the boiler. Do I just wire the 2.5mm into a 3A FCU and leave the 16A breaker? Is there any particular reason or benefit to having it on it's own circuit.

Yes

3. KITCHEN RADIAL TO RING
I currently have just 2 double sockets in the kitchen each 1 a radial from a 16A breaker. Because both cables run from the same point on the CU I would like to add more sockets inbetween ultimately turning this into a ring. I would like to add 1 more double, 1 single, an isolating switch for a 2400w single oven and 1 more single or an FCU for a cooker hood. I know the breaker will have to be changed to a 32A. Should I run the hood from a single socket with a plug or an FCU? Do I have to have another isolating switch for the cooker aswell as the hob or can they be wired into 1 dual switch and then independantly to the oven and hob using the 2.5mm and 4mm respectively?

I'd get the cables tested due to concerns about why the cables are radials, and to see if they are okay to convert to a 32a ring with MCB uprgarde to 32a. I would be tempted to renew the lot.

4. CHASING IN KITCHEN
I'm going to have to chase cables in all sections of the wall mid, corners, up near the ceiling for cooker hood. Can I run these in conduit or do they have to be protected with metal? Can anyone provide a link to show me what I need to be looking for along the lines of metal mechanical protection if that is whats required as I can only seem to find armoured cable. Does the metal protection have to be earthed?

Check out the Wiki for zone details for cable runs, metal conduit requires earthing.

here's a diagram taken from the Wiki

5. EXTEND LIGHT CABLE
Is it ok to extend a 1.5mm light switch cable using a junction box or should I run a fresh length. Would be much easier to extend. What AMP junction box should I be looking at for this cable. Is 16A ok?

Junction boxes are not allowed unless accessable, hence why they are installed in loft areas but not between grd / 1st floors, crimp or replace the complete run

Next time you post, please be more patient- most have day jobs so forum responses are always better in the evening.

Youre prompting for a reply an hour after your 1st post is likely to give peeps the humps and in turn the bums rush regarding detailed response

 

[JohnD]

this is far too long for me to grasp so I'll just reply to

"2. IMMERSION OUT BOILER IN
I have removed an old back boiler and am having a combi condensing boiler fitted. The old immersion (which has since taken a trip the scrap yard) was connected to a 16A breaker on 2.5mm cable. I would like to reroute this cable to run just the boiler. Do I just wire the 2.5mm into a 3A FCU and leave the 16A breaker? Is there any particular reason or benefit to having it on it's own circuit. "

I didn't see if you mentioned whether your CU was split load or what. Immersion heaters and boilers are two appliances that are very prone to small leakages and nuisance tripping of RCDs (due to the presence of water). So it is an advantage to have them on non-RCD radial circuits. I am going to guess that your immersion was not on an RCD circuit and so it would be good to put the boiler on the same circuit. If it is in a convenient position this wi also save running new cable. put a 3A fuse in the FCU unless you want to go to the trouble and expense of putting a new MCB in the CU. I think Memera MCBs only go down to 6A but a Memshield one will fit and they are available in lower ratings. Do not put a 13A socket on this non-RCD circuit.

 

[FirstTmeBuyer]

Hi thanks for the replies. I didn't wait an hour it was the night before when I made my first post. Just wanted to bump it.

The kitchen is very small and only has 2 doubles. 1 double is on an external wall and the cable goes through the cavity (not great I know and will be rectified and the other ran upstairs and down through the ceiling. Because of the position of the sockets and run of the cable I assume it was easier for the electrician to do it this way as a radial as a ring would have involved removing tiles from the lower half of the kitchen wall to chase in.

I wanted to run the oven from the ring as it is only 2.4kw 10A and thought that this kind of load is acceptable on a 32A kitchen ring. If it were more I would wire it separately like the hob. Should I really wire it separately or is it ok from the ring?

 

[FirstTmeBuyer]

Hi JohnD the CU is a mem AD10HED 10 way split load. The immersion breaker is in a non rcd slot so it should be ok to put it straight on to the boiler via a 3A FCU.

I did notify building control aswell and from what I understand it's ok to DIY as they will come and inspect the work done.