A ring circuit or two radials? What would you do?

[Argyll]

Another video.....sorry

I initially thought about having a ring circuit but then thought to save time (and cable) it might be best to have two radials instead. Let me know what you think.

[Neelix]

For a kitchen I usually use a 32A ring …… using 2.5mm cable

You could use a 32A on a 4mm radial but be careful as not all sockets can accept 2x 4mm cables


How do you intend to test this work ?

[Argyll]

For a kitchen I usually use a 32A ring …… using 2.5mm cable

You could use a 32A on a 4mm radial but be careful as not all sockets can accept 2x 4mm cables


How do you intend to test this work ?

I thought maybe 5 double sockets and two singles for the washing machine and dishwasher would be too much load but maybe I'm just overthinking it. It's not like they'd all be on at the same time anyway.

I'm having a new 12 way RCBO board fitted in the next few weeks. They'll make the connection and test it.

[Someone-Else]

If (Like most of us) you have a socket for a washing machine behind said WM it would be a good idea to have a double pole isolator for that socket above the work surface.
If your kitchen RCBO trips, you can isolate the WM socket by pressing the switch, not having to pull the WM out

As a side note: Since the advent of RCD's and RCBO's some folk are going back to having radials, (Particularly in kitchens) That way if you are not in and the kitchen RCBO trips, no one worries about a washing machine stopping, but they do worry about the fridge and or freezer thawing.

[ericmark]

If one reads the regs it suggests item which are fixed over 2 kW should be on a dedicated supply.

We don't tend to do this, more to do with tradition, washing machines were used by pulling out to centre room so were not fixed, and the kitchen could not be used for anything else, as cloths were everywhere.

Only when we got the front loader could we wash cloths and cook at the same time, but the washing machine used high power for a short time, so still no problem.

The washer/dryer however does use high power for an extended time, but the dryer did use high power for extended time, but the heat pump type use a lot less power and have an on/off cycle, so not so much of a problem.

So in the main a kitchen can function on a single ring final, and worse case scenario the overload trips, but use loads of radials you may stop the overload, but still only 60 - 100 amp supply so you run the risk of main fuse rupturing which is serious as you can't reset that.

So I would go for ring final.

[Neelix]

If one reads the regs it suggests item which are fixed over 2 kW should be on a dedicated supply.

We don't tend to do this, more to do with tradition, washing machines were used by pulling out to centre room so were not fixed, and the kitchen could not be used for anything else, as cloths were everywhere.

Only when we got the front loader could we wash cloths and cook at the same time, but the washing machine used high power for a short time, so still no problem.

The washer/dryer however does use high power for an extended time, but the dryer did use high power for extended time, but the heat pump type use a lot less power and have an on/off cycle, so not so much of a problem.

So in the main a kitchen can function on a single ring final, and worse case scenario the overload trips, but use loads of radials you may stop the overload, but still only 60 - 100 amp supply so you run the risk of main fuse rupturing which is serious as you can't reset that.

So I would go for ring final.

I always think of the 2kw rule applying to hard wired appliances rather than items you plug in

[ericmark]

I always think of the 2kw rule applying to hard wired appliances rather than items you plug in

Back in the 1950's the immersion heater was plugged in, normally with a 15 amp plug, so the plumber could change it without calling the electrician.

What we look at is if normally moved, so your twin tub which was dragged into centre of floor on washing day, is a portable appliance, technically if the washing machine is on wheels it is portable, but if not moved for weeks on end, then really should be looked at in same light as the hand drier, oven, and immersion heater.

The bit is:-
"The load current in any part of the circuit should be unlikely to exceed for long periods the current-carrying capacity of the cable (Regulation 433.1.5 refers). This can generally be achieved by:
(i) locating socket-outlets to provide reasonable sharing of the load around the ring
(ii) not supplying immersion heaters, comprehensive electric space heating or loads of a similar profile from the ring circuit
(iii) connecting cookers, ovens and hobs with a rated power exceeding 2 kW on their own dedicated radial circuit
(iv) taking account of the total floor area being served. (Historically, limit of 100 m² has been adopted.)"

This is not a strict rule, it is in the appendix 15 (informative) back with the 14th edition we go a lot of info on how to comply, but today we have independent guides, there have always been guides, some from IEE (now IET) and some from the Unions, today the electrical safety council also publish best practice guides, mainly as the English used is not always plain, I wonder if this is on purpose? The division of the installation into circuits springs to mind, the putting of multi circuits on one RCD did not to me seem to comply, but it depends what you read into the regulations.

To me the problem is the 13 amp socket is designed for 7/0.029 cable, slightly larger than 2.5 mm² and to get three 4 mm² or even worse three 6 mm² cables into the socket is asking for poor connections, and to use 2.5 mm² as a radial limits one to 20 amp, and it becomes too easy to plug in items exceeding 20 amp.

I still remember the pre-war fuse boxes, with a row of rewireable fuses, one for each socket. With MCB's they became cheap enough, but the RCBO is more expensive, and also the box gets bigger and bigger, the ring final means smaller consumer unit and less expense, and has since designed at the end of world war two proved to be a good system, and if it's not broke don't fix it.

I have ring finals in both of my kitchens, one for lower floor, and one for west side upper two floors and one East side upper two floors, so five ring finals, splitting front to back rather than up down means a more even load, and less cable, so a better loop impedance, also a 40 amp RCBO for the showers, so with 14 RCBO's I could easy exceed the 60 amp supply to the house, but it never has, it would be expensive if it did rupture as we would likely loose all food in freezers.

But the only time any RCBO has tripped is when my roof leaked and water got into a socket, in general our power use has gone down, in theroy my cooker can use over 60 amp, but it has never tripped the 32 amp RCBO. Although one ring can use 3.7 kW other than boiling water with an induction hob it would burn the food using that much power, it is more economical than all previous cookers so why should it need more power?

For a commercial kitchen yes may want radials, but domestic a kitchen ring final is fine.

[Argyll]

If (Like most of us) you have a socket for a washing machine behind said WM it would be a good idea to have a double pole isolator for that socket above the work surface.
If your kitchen RCBO trips, you can isolate the WM socket by pressing the switch, not having to pull the WM out

Good shout. I'll install a spur from the ring circuit and install an FCU above the worktop

[Neelix]

If (Like most of us) you have a socket for a washing machine behind said WM it would be a good idea to have a double pole isolator for that socket above the work surface.
If your kitchen RCBO trips, you can isolate the WM socket by pressing the switch, not having to pull the WM out

Good shout. I'll install a spur from the ring circuit and install an FCU above the worktop

I tend to put the socket in the adjacent cupboard