Double or two singles?

[liftman]

I have read on here that it is not a good idea to plug a washing machine and a tumble dryer into the same double socket due to load on the socket, i was planning to do this when i re-fit my kitchen, so am now wondering if it is a better idea just to make the double into two singles, to avoid this problem. Any help would be appreciated. Also is there a limit to loading on a 2.5mm ring main?

 

[ColJack]

2.5mm ring main is subject to the limitations of it's protective device.. ( if you have a 32A breaker on it then you can only load it to 32A )

it is advisable to distribute the loads evenly around the ring because if your kitchen is at one end or the other, then the shorter leg will take more of the current than the long leg..
for this reason, it is now common practice to put kitchens on their own ring..

as for heavy loads on double sockets, yes it's better to put them as 2 singles....

even a double socket is only designed to handle 13A.. that's total, not each outlet.. it even says so on the back of most of them.. ( though joe public normally thinks this means for both outlets.. )

 

[ban-all-sheds]

That's not what BS 1363 says.....

 

[ericmark]

I have seen on here a few times that a 13A double socket can't handle 26A but I have failed to find any manufactures who include that in their spec sheets. And I am inclined to think it is some more miss-information. This happens all the time I had a big argument with my daughter who got these silly things one can stick into sockets.

and until some one can point me to manufactures statement that their sockets can't handle two 13A items I will not believe it.

As to overload by having too many sockets at one end of ring main I did try to calculate how close to one end they would need to be and I very quickly realised it is very unlikely to happen.

However what is a problem is the grid switches used to feed washing machine, tumble dryer etc. Are rated at 20 amp so there is an issue here when fitting double sockets. The grid switches can also take fuse holders or can be feed with 20A radials from consumer unit.
I do recommend grid switches on supply to washing machine. If you have ever seen one where the weights have become lose you would realise why. If that happens without a grid switch only way is to switch off at consumer unit as far too dangerous to put hands near washing machine.

I think it is the 20A switch which has started the rumour about about the sockets and it has been changed slightly in the telling.

So if using Grid switch then yes two sockets are required.

As to loading a ring main is normally 32A and Dishwasher, Washing Machine, Oven, Tumble dryer, and kettle are all near the 13A limit so if any of these can be given their own supply it will reduce the total load on the kitchen ring.

A radial is normally 20A and to feed single sockets for Oven (Not Hob as that is well over 13A) Fridge, Freezer, Washing Machine, etc. will help.

There is some disagreement as to Fridge, Freezer some say to put on their own supply could me you would not notice if the supply tripped until too late, others point out it is a lot less likely to trip in first case. I know a friend of mine put them with the intruder alarm as when power to that trips it starts a sounder so unlikely to not notice when tripped.

But unless RCBO's are used that would not help anyway.

So I would suggest you talk to who is doing the job and get advice from someone on site which is far better than asking anyone remote from the job.

Maybe they are using Ali-tube cable and naming the Fridge, Freezer sockets. There are so many options I could write 5 or 6 pages and still miss out bits. So ask the guy doing the Part P cert and see what he thinks.

Missed slash out on img so corrected

 

[holmslaw]

..

 

[ericmark]

BS 1363 does not stipulate the maximum load for 13A socket outlets.

The only pointer to the maximum load is that they have to pass a temperature rise test.
For a single the test load is 14A.
For a double the test load is 20A, 14A in one socket 6A in the other.
For a unfused multiple [triple or more] the test load is 28A, 14A in two of the sockets
For a fused multiple [triple or more] the test load is 20A - evenly distributed across all the sockets.

Thank you that does explain where it comes from. In my house a mistake was made and both tumble drier and washing machine were feed from same FSU there have been two washers and two driers used since first wired some 20 odd years ago and they have never blown the fuse. So I have not bothered changing it. Not saying it is right but one wonders if these sockets which failed had some other problem which caused them to fail?

 

[ban-all-sheds]

So if using Grid switch then yes two sockets are required.

What difference does it make to the socket if there's a switch in its supply cable?

 

[ban-all-sheds]

BS 1363 does not stipulate the maximum load for 13A socket outlets.

The only pointer to the maximum load is that they have to pass a temperature rise test.
For a single the test load is 14A.
For a double the test load is 20A, 14A in one socket 6A in the other.
For a unfused multiple [triple or more] the test load is 28A, 14A in two of the sockets
For a fused multiple [triple or more] the test load is 20A - evenly distributed across all the sockets.

So in other words BS1363 does stipulate the maximum load that a product has to be able to withstand and not get damaged.

If a manufacturer makes a socket, and 20A is the maximum it can support then it complies with BS 1363.

I suppose you could argue that the limit should more accurately be described as the minimum...

Nothing to stop him making one which exceeds the requirement though - I believe MK do.

Which version is that from, BTW?

I've got a copy of

BS 1363:1984
Incorporating
Amendment Nos. 1, 2,
3, 4, 5 and 6

and the table in that has slightly different figures, so I'd like to update it.

 

[holmslaw]

..

 

[ban-all-sheds]

I believe its a complete rewrite, but table 5 is very similar.

The only change is to the unfused multiple - still 20A but it used to be 14A + 6A (i.e. the same as the double).

Funny thing is a twin is tested at 20A and an unfused triple is tested at 28A, so I assume it is ok to put two 3kw appliances on a triple but not on a twin

TBH I didn't know you could get unfused multiples....

 

[holmslaw]

..

 

[JohnD]

I do recommend grid switches on supply to washing machine. If you have ever seen one where the weights have become lose you would realise why. If that happens without a grid switch only way is to switch off at consumer unit as far too dangerous to put hands near washing machine.

You are thinking here of an appliance socket that is behind the appliance?

It is common practice, and a good idea, to handle this by putting a DP switch (or FCU) above the worktop, to feed an single unswitched outlet below. This is also very neat.

 

[ColJack]

yeah but takes up a butloat of space above the counter if your appliances are all grouped close together..

 

[JohnD]

I like one switch above each appliance (or space where an appliance might one day be) or below e.g. cooker hood

very easy to chase and run cable

View media item 4496

 

[ColJack]

nice if you've got the room..

I've got a large window in my kitchen, under which will be the sink and the washing machine and dishwasher nearby..
the only space i've got is about 250mm for a double socket and the switches for the dishwasher and washing machine ( boiler protrudes for the rest on one side, the other side will be over the drainer.. )

just out of curiosity, why does it switch from running through the top holes, to the bottom ones and back for the cooker hood switch ( presumably )