Washing machine and new consumer unit

[Risteard]

...and, of course, other items on the circuit - it's unlikely to be a separate circuit for the WM.

It's very common in the social housing stock here to have dedicated circuits for the likes of washing machines.

 

[EFLImpudence]

Really.

 

[JohnW2]

It's very common in the social housing stock here to have dedicated circuits for the likes of washing machines.

When you say "dedicated circuit", do you mean with its own dedicated RCD or RCBO (since that is what would be relevant in terms of the way this issue arose in discussion)?

Kind Regards, John

 

[Taylortwocities]

Isn't it strange that different parts of the UK seem to have different ways of doing things.

 

[JohnW2]

Isn't it strange that different parts of the UK seem to have different ways of doing things.

I don't think that it's all that strange. If you look at, say, what people drink and eat (or what 'language they speak), there's a fair bit of regional variation just within England!

Kind Regards, John

 

[Iggifer]

We generally do appliance radials. It's usually one for a washing machine and one for a dishwasher/tumble dryer depending on the kitchen layout. One of these radials will also supply a fridge/freezer (or one on each if separates).

A lot of kitchens we do are also just a 20A 2.5 radial for the oven. Seems round these parts single ovens are more popular than anything meatier.

 

[JohnW2]

A lot of kitchens we do are also just a 20A 2.5 radial for the oven. Seems round these parts single ovens are more popular than anything meatier.

If you believe in diversity, a 20A/2.5mm² circuit can support an oven/cooker of about 9.9kW - which I would call "fairly meaty" .

Kind Regards, John

 

[AndyPRK]

2.5mm for an oven point. Well I never.

Bit screwed if they want an electric hob though.

What isolator do you use? A 45A one or 20A ?

Is this because you don't want to stock 4mm or 6mm ?

 

[Iggifer]

Nope, like I say, it depends on the spec. The last kitchen we did was a 6mm², and the kitchen before that was a 10mm² (induction hob), but maybe the last 9 before that were just 2.5mm² for a single oven and gas hob.

If it were down to me, I'd happily just install 4/6mm² but I don't spec or price the jobs so not down to me. You're right, if they want to change to an electric hob in the future, they're gonna need a new cable putting in. BUT, you could say that about a lot of stuff that gets installed.

20A DP switches generally. Not much sense in using a 45A

 

[ericmark]

Interesting, I have always said that since washing machines, tumble driers, dish washers, and ovens are all over 2 kW using the advice in the appendix of the BS7671 then they should have dedicated circuits. There is also the fact any RCD measures current unlike the ELCB-v which measured voltage, and it trips when the current goes over the rated value, so it has to be an over current device even if that current is not the current being used. So by definition a RCD creates circuits. So in my house I have two circuits which are then sub-divided into 4 other circuits. I don't have a consumer unit I have two fuse boxes which have had the fuses replaced with MCB's. The point is some one has to decide how to interpret rules, regulations and laws. And we all have our own ideas on how we should do this. In the main we realise to use all RCBO's would be the best option and having separate feeds to each fixed appliance i.e. items not designed to be put away after use, or having carrying handles. But the cost would be very high, so we have to strike a balance between price and the ideal installation. For commercial where you need to pay for some one to attend to reinstate power use of RCBO's makes a lot more sense, but we do not include the cost of a house holders time to reset a RCD. So we reduce costs by using just two.

 

[EFLImpudence]

Interesting, I have always said that since washing machines, tumble driers, dish washers, and ovens are all over 2 kW using the advice in the appendix of the BS7671 then they should have dedicated circuits.

Apart from Appendix 15 being only advisory, it doesn't say that.

It says cooking appliances over 2kW which could be why we put cooking appliances on separate circuits.
The other stipulation is loads similar to immersion heaters and comprehensive space heating - presumably 3kW and over.

I think this has been pointed out before.

 

[JohnW2]

Apart from Appendix 15 being only advisory, it doesn't say that. .... It says cooking appliances over 2kW which could be why we put cooking appliances on separate circuits. The other stipulation is loads similar to immersion heaters and comprehensive space heating - presumably 3kW and over. I think this has been pointed out before.

Quite so - and, furthermore, what it is really talking about (the fact that it's in App 15 is the clue!) is that, in order to reduce the risk of overloading part of the cable, there are certain high loads (particularly long-lasting ones) which are probably best not connected to a ring final circuit.

As I've always said, I don't really think that even if things like cooking appliances or water heaters etc. produce overloads of some part of a ring final (which, in itself, is unlikley), in reality any such overloads are unlikely to persist for appreciable periods of time. In contrast, things like fan heaters (particularly if more than one) are probably more likely to result in 'problems', even though I don't think they qualify as "comprehensive space heating". I wonder if anyone, eric or otherwise, installs dedicated circuits for fan heaters?!!

Kind Regards, John

 

[JohnW2]

There is also the fact any RCD measures current unlike the ELCB-v which measured voltage, and it trips when the current goes over the rated value, so it has to be an over current device even if that current is not the current being used. So by definition a RCD creates circuits.

I presume that you are talking about the BS7671 definition of "a circuit" - but, if so, and with respect, I think that interpretation is rather silly. BS7671 says that a circuit is an "assembly of electrical equipment .... protected against overcurrent by the same protective device". I think that we (and BS7671) all know what "protected against overcurrent means" and that is does not mean that the residual current detected by an RCD has gone over a threshold!!

Kind Regards, John

 

[ericmark]

As you know the writers of BS7671 are very aware of English used, swapping phrases like rule of thumb to historical. So if they mean over non leakage current or over leakage current I am sure they would stipulate, likely in the definitions section.

Most British Lawyers are very good at reading English. If it were a statement by a layman I would accept that they mean current protected by the MCB not RCD, just like a statement using a double negative is likely an error. But BS7671 is hardly a layman's book.

 

[bernardgreen]

unlike the ELCB-v which measured voltage

The ELCB-v that I met was a 200 ohm coil that operates the trip when 20 mA flowed through the coil. For 20 mA to flow the voltage across the coil had to be 40 volts.

One end of the coil of ELCB-v is connected to the "Earth" wiring ( CPC ) in the house and the other end to a Ground Rod driven into the ground. If the resistance of the Ground Rod was also 200 ohms the CPC would have to reach 80 volts above ground before enough current could flow through the coil to trip the ELCB-v

I believe that genuinely voltage operated devices were available with coils of much higher resistance ( impedance ) and these tripped on less than 1 mA but these often tripped during thunderstorms when the potential of the ground was bounced by a lightning strike somewhere near by.