How much power can be got from a socket?

Worztron · 27-03-2014 2:25pm #1

Hi.

How much power can be got from a socket? What would happen if it was overloaded?

Example scenario:
For testing things on my old PC, I connect a 20 inch CRT monitor + Desktop PC + Speakers to a single socket.

Is this well within safety margins?

Cheers.

liveandnetural · 27-03-2014 2:58pm

BS1363-2:1995 requires for double socket outlets that both socket outlets have loads applied via test plugs, 1 test plug having a load of 14 amps whilst the other has a load of 6 amps, making a total load of 20 amps on the cable supplying the double socket outlet. The double socket outlet is then subjected to this loading for a minimum continuous period of 4 hours or longer until stability is reached with a maximum duration of 8 hours (stability being taken as less than 1 degC rise within 1 h). The test is passed if neither the terminals / terminations, nor the accessible external surface, increase in temperature by more than 52 degC.

your safe enough with your pc stuff

Worztron · 27-03-2014 3:04pm

liveandnetural wrote: »

BS1363-2:1995 requires for double socket outlets that both socket outlets have loads applied via test plugs, 1 test plug having a load of 14 amps whilst the other has a load of 6 amps, making a total load of 20 amps on the cable supplying the double socket outlet. The double socket outlet is then subjected to this loading for a minimum continuous period of 4 hours or longer until stability is reached with a maximum duration of 8 hours (stability being taken as less than 1 degC rise within 1 h). The test is passed if neither the terminals / terminations, nor the accessible external surface, increase in temperature by more than 52 degC.

your safe enough with your pc stuff

Thanks for the explanation.

tomdempsey200 · 27-03-2014 3:08pm

I think the double sockets are rated up to 20amp total

sockets and plugs give trouble with heavy sustained loads

bassey · 27-03-2014 9:36pm

Sockets on a 20A MCB/fuse so neglecting power factor you can draw 4.6 kW from the wall

brightspark · 27-03-2014 10:42pm

bassey wrote: »

Sockets on a 20A MCB/fuse so neglecting power factor you can draw 4.6 kW from the wall

its possible for the socket to be on a 32A MCB (ring circuit)

27-03-2014 10:47pm

Worztron wrote: »

Hi.

How much power can be got from a socket? What would happen if it was overloaded?

Example scenario:
For testing things on my old PC, I connect a 20 inch CRT monitor + Desktop PC + Speakers to a single socket.

Is this well within safety margins?

Work out the total load that you would like to draw from a single socket. Your example is likely to be a relatively small load, I would guess that it is under 6 amps, so well within safety margins.

tomdempsey200 · 27-03-2014 10:56pm

brightspark wrote: »

its possible for the socket to be on a 32A MCB (ring circuit)

the 'draw' is limited by the connected load

or should be

brightspark · 27-03-2014 11:06pm

tomdempsey200 wrote: »

the 'draw' is limited by the connected load

or should be

Of course it is, the max continuous draw from a twin socket can only be 2x13Amps (assuming accurate fuses in plug tops.

But the OP won't be be drawing anything near that with the load mentioned.

liveandnetural · 28-03-2014 3:37am

brightspark wrote: »

Of course it is, the max continuous draw from a twin socket can only be 2x13Amps (assuming accurate fuses in plug tops.

But the OP won't be be drawing anything near that with the load mentioned.

according to mk its

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.

brightspark · 28-03-2014 8:14am

My initial post replying to Bassy, was to highlight that not all twin sockets are protected by a 20A MCB and that it was possible for a 32A MCB to be used. It is also likely that in an older installation the fuse (DZ2 type) might only be 16A on a radial circuit. (I think older ring circuits were protected by a 20A DZ2 fuse, but
I'm not certain)

But on a 32A ring circuit it is possible BUT NOT RECOMMENDED to plug in two 13A loads without tripping a circuit breaker! The total load then only being limited by the fuses in the plug tops.

In an average house I would expect the only place where two large loads would normally be located close together is in a kitchen, where ring circuits are now prohibited.

Perhaps the fact that a twin socket outlet is only able to safely supply a max current of ~20A, is reason why radial circuits protected by a 20A MCB should always be used in preference to ring circuits that are protected by a 32A MCB.

And liveandneturals post would indicate that even 20A is slightly too high!

Bruthal · 28-03-2014 4:55pm

brightspark wrote: »

And liveandneturals post would indicate that even 20A is slightly too high!

Dont forget the 20A MCB wont trip too quickly, if at all, with both sockets of a twin fully loaded to 13 amps each.

tomdempsey200 · 28-03-2014 4:59pm

well that's it

the OCPD is specifically designed to protect the final circuit cable not the accessory

although afaik the accessories are usually closely matched anyhow

the ring circuit is an anomaly anyhow in this regard and will prob eventually be eliminated altogether for domestic use

it will still be useful for commercial and industrial though

liveandnetural · 29-03-2014 1:32am

tomdempsey200 wrote: »

well that's it

the OCPD is specifically designed to protect the final circuit cable not the accessory

although afaik the accessories are usually closely matched anyhow

the ring circuit is an anomaly anyhow in this regard and will prob eventually be eliminated altogether for domestic use

it will still be useful for commercial and industrial though

i would dissagree with this statment about ring circuits still very common to see them especially in large domestic instlations

tomdempsey200 · 29-03-2014 7:04am

liveandnetural wrote: »

i would dissagree with this statment about ring circuits still very common to see them especially in large domestic instlations

yes that was their main use from my point of view
a couple of rings circuits is a great job in addition to kitchen and utility radials

do you not believe they will eventually be phased out of domestic use?

unless they changed the rules that conductor size must match breaker size.. same as industrial ring ccts

frankmul · 29-03-2014 7:38pm

tomdempsey200 wrote: »

unless they changed the rules that conductor size must match breaker size.. same as industrial ring ccts

I always thought that the cable was sized bearing in mind the mcb used?

29-03-2014 7:46pm

frankmul wrote: »

I always thought that the cable was sized bearing in mind the mcb used?

Calculate the design current, select a proactive device based on this, then select a cable that has a current carrying capacity that exceeds the rating of the protective device. Finish off by making sure that fault loop impedance and volt drop are not excessive and respecify the cable if required.

frankmul · 29-03-2014 8:44pm

2011 wrote: »

Calculate the design current, select a proactive device based on this, then select a cable that has a current carrying capacity that exceeds the rating of the protective device. Finish off by making sure that fault loop impedance and volt drop are not excessive and respecify the cable if required.

That's what I thought, I'm not sure what tomdempsey200 means

tomdempsey200 · 29-03-2014 9:01pm

im saying that at the moment on domestic ring final circuits

a 2.5mm conductor may be used on a ring circuit protected by a 32 amp mcb

not a problem if the ring circuit stays intact

im saying they may change the rules so that the current rating of the conductors forming the ring is greater than the mcb rating

and they may not do this of course..

they may do nothing..

they may scrap the domestic ring circuit altogether..

29-03-2014 9:06pm

tomdempsey200 wrote: »

im saying that at the moment on domestic ring final circuits

a 2.5mm conductor may be used on a ring circuit protected by a 32 amp mcb

not a problem if the ring circuit stays intact

I am not a fan of ring socket circuits.
However what you have is two x 2.5 T+E supplying the load, not one.
So effectively a 5sq. conductor.

im saying they may change the rules so that the current rating of the conductors forming the ring is greater than the mcb rating

This is already the case. A "5 sq." can take in excess of 32A.

tomdempsey200 · 29-03-2014 9:11pm

2011 wrote: »

I am not a fan of ring socket circuits.
However what you have is two x 2.5 T+E supplying the load, not one.
So effectively a 5sq. conductor.

This is already the case. A "5 sq." can take in excess of 32A.

yes.. obviously if the ring circuit is intact

but if not there's a potential for overload

historically with 'domestic' there may not be competent people in charge of maintenance..to put it mildly

and the rules can reflect this

the circuit is idiot proofed by matching physical conductor size to mcb

29-03-2014 9:48pm

tomdempsey200 wrote: »

yes.. obviously if the ring circuit is intact

Yes, it must be intact.

but if not there's a potential for overload

I don't know what you mean by this.
Please explain.

historically with 'domestic' there may not be competent people in charge of maintenance..to put it mildly

and the rules can reflect this

the circuit is idiot proofed by matching physical conductor size to mcb

No regulations can prevent stupidity.

tomdempsey200 · 29-03-2014 9:56pm

2011 wrote: »

I don't know what you mean by this.
Please explain.

i will provide an answer to your question tomorrow

if you don't figure it out in the interim

29-03-2014 9:58pm

tomdempsey200 wrote: »

i will provide an answer to your question tomorrow

if you don't figure it out in the interim

The suspense is killing me, I won't be able to sleep

:D

Talk tomorrow.

Bruthal · 29-03-2014 9:58pm

2011 wrote: »

I don't know what you mean by this.
Please explain.

Im sure he means a 5 square conductor has potential to become a 2.5 conductor at any time, and could be loaded above 2.5 rating.

Its a long time ago I said I am not a fan of ring circuits. They just dont seem like a proper electrical method, at least in my mad mind anyway.

tomdempsey200 · 29-03-2014 10:21pm

Bruthal wrote: »

Im sure he means a 5 square conductor has potential to become a 2.5 conductor at any time, and could be loaded above 2.5 rating.

Its a long time ago I said I am not a fan of ring circuits. They just dont seem like a proper electrical method, at least in my mad mind anyway.

i like them

ring final( commercial and industrial) and ring mains

but domestic ..maybe they'll make another change

Bruthal · 29-03-2014 10:26pm

tomdempsey200 wrote: »

i like them

ring final( commercial and industrial) and ring mains

but domestic ..maybe they'll make another change

I never wired one in a house.

29-03-2014 10:33pm

Bruthal wrote: »

Im sure he means a 5 square conductor has potential to become a 2.5 conductor at any time, and could be loaded above 2.5 rating.

If the ring became 2 radials ?
The same applies to any circuit fed by parallel conductors.

I don't like them, either but when the ring is unbroken the cables are protected.

Bruthal · 29-03-2014 10:39pm

2011 wrote: »

If the ring became 2 radials ?
The same applies to any circuit fed by parallel conductors.

One of those newly formed radials could be supplying the entire load originally on the ring. Therefore, potential for overloading.

deandean · 29-03-2014 11:00pm

I run two, 3kw kettles from a twin MK socket the odd time and all is well. that's about 24A for a few minutes.

30-03-2014 12:02am

Bruthal wrote: »

One of those newly formed radials could be supplying the entire load originally on the ring. Therefore, potential for overloading.

Potential alright, if there is a failure.
Same with many circuits fed by parallel conductors, but I take your point.

How much power can be got from a socket?

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