too much load on a spur?

[nrgizerbunny]

I am confused here!

does that mean its okay to plug a washing machine and drier into a double socket or would i have to get two singles and then plug them in adjacent to each other?

 

[masona]

This is what I can't understand, a single socket rated 13 amp and a double socket is also rated 13 amp and yet you cannot plug 2 appliance if they are needed for 13 amp each. So am'I right saying you can only plug for example 6.5 amp in each of the double socket for the total rating of 13 amp? If you have 2 single socket side by side, what is the difference?

 

[Jaymack]

The advice and statements by some contributors to this forum must be treated with caution. There are no experts, we are all learning. I hope the following dissertation, clears the confusion which has arisen on what is a fairly important topic.

The current rating for the twin socket, is greater than that of the single socket and is largely due to the increased thermal heat dissipation, in the case of the twin socket. The rating of any electrical carrying conductor whether a cable, copper bar etc., obviously depends on the rate at which the heat is transferred to the surroundings. There is an increased surface area and thermal mass in the case of the twin socket, this is variable and depends upon the manufacturers’ design. The total thermal current rating for 2 plugs in the same twin socket, is above 13A for both; but not double (26A), it is about 19A (see the article below), but the specific manufacturer must be consulted for recommendations.
Fortunately, for most situations, this is not something to worry about, diversity would be applicable, where two appliances are plugged into the same twin socket outlet, i.e. it would be very unusual to have two appliances, each continuously pulling 13A).

The following article is from MK: -

All MK socket-outlets are manufactured to comply with BS1363 part 2: 1995 and are rated at 13A per unit. Double socket-outlets have been manufactured and tested to exceed this rating by margin that allows electrical safety and reduces the risk of heat and mechanical damage to components due to overloading. It should be noted that BS1363 part 2: 1995 does not allow double sockets to operate at twice the permissible maximum loading and it should be remembered that double socket-outlets are not manufactured to be able to withstand a 26A load for sustained periods of time.

Research by ourselves and third party organisations has shown that all MK double sockets can safely withstand a continuous load of 19.5A for an indefinite period. Increasing the load slightly will begin to cause heat and mechanical stresses on the components in a relatively short period. Testing showed that a load of 22.3A was sufficient to cause heat stress that would cause a browning of the faceplates and sufficient heat to cause insulation damage to cable cores. A load of 24A for 43 hours was sufficient to cause significant heat damage to the material in which the socket-outlet was situated and within 75 hours sufficient to cause significant damage that would lead to the very real potential of fire.

MK recommend that users of their sockets consult professional design Engineers when designing installations to avoid the possibility of heat and mechanical stress to components and installations caused by overloading of MK socket-outlets.

Striving for perfection in an imperfect world.

 

[securespark]

This is what I can't understand...... If you have 2 single socket side by side, what is the difference?

The difference is that each single socket can safely withstand a loading of 13A, whereas if the two appliances were plugged into a two gang socket (also rated at 13A), then there is a danger (with both appliances on together) that the 13A maximum will be exceeded.

The advice and statements by some contributors to this forum must be treated with caution. There are no experts, we are all learning.

The advice and statements by some contributors to this forum naturally err on the side of caution. If the official safe limit of a BS1363 socket outlet is 13A, then that figure should not be exceeded, and that goes for all outlets, be they single, double, triple sockets or spurs.

What you write about doubles having a greater current rating is piffle.

MK recommend that users of their sockets consult professional design Engineers when designing installations to avoid the possibility of heat and mechanical stress to components and installations caused by overloading of MK socket-outlets.

Exactly. Good design will avoid any situation where overload is likely - and in many cases good design includes where possible capacity for further loading. A professionally designed and installed circuit will not allow the rating of 13A per outlet to be exceeded.

No experts, only learning, eh? Well, I agree with the latter part of that, but not the former.

You are certainly no expert, posting that unqualified drivel. Why on earth sanction the loading of an electrical accessory beyond it's safe, designed, intended loading?

Would you say the same of a 32A DP switch? Oh, it's OK, load it up to 50A, it'll be OK.

Or a 6A switch to 20A? Or an 63A incomer to 100A?

Get real.

 

[plugwash]

the thing with doube sockets is you can't tell how those who don't know that they are only rated at 13A (which includes most laypeople) are going to load them.

how do you know someone won't come along to do a disco and put 3KW of lighting (which isn't a great deal if you are using say par64 spots) on each side of the double socket that happened to be nearest thier rig?

how do you know someone won't feel rather cold and plug in two bar fires to the same socket?

ok in a few situations like the semi-fixed appliances in kitchens you can account for the heavy load appliances but not in normal wiring practice.

 

[HDRW]

A professionally designed and installed circuit will not allow the rating of 13A per outlet to be exceeded.

By definition, there is nothing to stop someone plugging a 13A load into each socket. Please tell me how you design and install a circuit that includes twin 13A sockets, in such a way that only 13A can be drawn from the pair. Are you proposing that twin sockets are never used?

Cheers,

Howard

 

[securespark]

Howard -

In certain situations, yes.

That is what I mean by good design. If you have an installation where you know there is going to be more than one 13A appliance installed (ie in kitchen for washer and dishwasher), you ensure that for every appliance, there is one single outlet.

As Plug says, you cannot rule out abuse altogether. In the example Plug gave of using plug-in heaters, when you are designing the installation, you could look at the provision of heating systems in the property - if there is an efficient storage heater or CH system, then it is less likely portable heaters will be used, not impossible, I know.

No installation can be entirely foolproof (at least not within my costings!), but you plan the installation as best you can to try and reduce the possible abuse.

 

[Jaymack]

securespark wrote: -

The difference is that each single socket can safely withstand a loading of 13A, whereas if the two appliances were plugged into a two gang socket (also rated at 13A), then there is a danger (with both appliances on together) that the 13A maximum will be exceeded.

If this is the case, how would you prevent any user exceeding the loading of 13A on a double s.o., which I'm sure happens every day. Why is there no warning notices on such socket outlets, "Do not exceed the loading of 13A".

securespark wrote: -

Would you say the same of a 32A DP switch? Oh, it's OK, load it up to 50A, it'll be OK.

The parallel is not relevant, this statement implies that you are failing to grasp the argument, vis-a-vis the rating of double socket outlets and diversity.

MK are respected manufacturers of electrical accessories, they have stated: - "Research by ourselves and third party organisations has shown that all MK double sockets can safely withstand a continuous load of 19.5A for an indefinite period". What is it that you don't understand here?.

 

[masona]

securespark wrote: -

The difference is that each single socket can safely withstand a loading of 13A, whereas if the two appliances were plugged into a two gang socket (also rated at 13A), then there is a danger (with both appliances on together) that the 13A maximum will be exceeded.

If this is the case, how would you prevent any user exceeding the loading of 13A on a double s.o., which I'm sure happens every day. Why is there no warning notices on such socket outlets, "Do not exceed the loading of 13A".

Have to agreed with"Do not exceed the loading of 13A" because as a guess I would say about 90% of the population wouldn't have a clue, they see a plug and put it into the socket including children. Why don't they come up with a built-in 19 amp fuse in the double socket to prevent overloading?

 

[Damocles]

The thing to watch with putting single sockets all over the place is that someone comes along and uses a 4-way extension lead on the kitchen worktop with the kettle, toaster, washing machine and microwave all plugged into it. Ok, it will still have a 13A fuse but....

I remember reading the issue of loading comes down to heating of the socket. So use two single each rated at 13A. Except that much of the heat gets dissipated through the cable. So if you only have 6 inches of cable going directly from one single to a second single then you have negated the reason for separating them. they will still heat each other.

 

[securespark]

If this is the case, how would you prevent any user exceeding the loading of 13A on a double s.o., which I'm sure happens every day. Why is there no warning notices on such socket outlets, "Do not exceed the loading of 13A".

I can't. But avoiding situations where overload is possible can reduce the potential for abuse. What is it that you don't understand here? I said this in my last post.

The parallel is not relevant, this statement implies that you are failing to grasp the argument, vis-a-vis the rating of double socket outlets and diversity.

MK are respected manufacturers of electrical accessories, they have stated: - "Research by ourselves and third party organisations has shown that all MK double sockets can safely withstand a continuous load of 19.5A for an indefinite period". What is it that you don't understand here?.

Why is it not relevant? I am not arguing about diversity, just about the 13A maximum for BS1363 outlets.

At the risk of repeating myself again, I understand what MK are saying.

What I am saying is that from my POV as a professional qualified spark, I cannot possibly justify a circuit where an outlet overload may occur, if that overload were avoidable by good design.

 

[securespark]

...someone comes along and uses a 4-way extension lead... Ok, it will still have a 13A fuse but.....

That scenario of a 4-way lead plugged into a single outlet is similar to a hard wired fused spur feeding several outlets. If the load attached exceeds 13A, the fuse blows.

 

[mapj1]

Further water on troubled oil - even the beloved ring main design itself is not suitable if practically all the load is at one point (unless by luck, that one point is the 'centre point' i.e. equidistant from the supply.) Otherwise the current sharing can be very unequal, and it is quite possible to cook the cable on one side, while staying within the rating of the 32A breaker.
(and how many people derate ring main cables when they share capping? They probably should, at least in places where the load is total ,like drops to the consumer unit at least, but it works out in practice)
The saving grace is that in reality the thermal time constants of both sockets and cables buried in the wall are long - perhaps 20-30 minutes to reach steady state temperature. Usually by then the load is back off again.
If we were worried we'd look to the continental practice of using C type 16A MCBs, same surge rating as a B32, but a thermal rating that matches the cable in use. Oddly the loading is about the same as a UK ring main, and overload problems are very rarely seen.
However, if you have good reason to believe, at the design stage, that there will be a serous risk of overload, it is only responsible to allow for this properly.
PS many triple sockets are 13A fused.!

Extend the ring, and if you think both sockets will be fully loaded together, better make it 2 singles side by side.

 

[Jaymack]

Agreed that there should be dedicated circuits for load points in areas such as kitchens, including the use of single socket outlets where warranted. As far as ring final circuits are concerned, these should be phased out IMO, too many problems with broken ring circuits and unequal loading etc., there appears to be a move towards the continental wiring method using radial circuits. Further, I've read elsewhere that the latest thinking over there has radial sub-main circuits from a main C.U. to rooms with mini-consumer units for the lighting and power within the rooms, this seems an overkill on the face of it.

 

[securespark]

Bu**er me!!

Something we all agree on! Rings are cr*p!

I used to think they were better than radials, being fed from both ends, but not now.