Safe bulb wattage for 13 amp ring

[Cctheatre]

hi - it s ages since I have had to work out the maximum bulb wattage I can use on a touring rig which goes to venues using a 13amp ring I did have the formula written down somewhere but for the life of me can’t find it. I want to use 12 lanterns but don’t want to overload. Can anyone advise please?Thanks

[timsabre]

Watts = volts x amps

 

so for a single 13A socket, 240 (ish) x 13 = 3120W

 

Usually we say 3KW to make it easy ... you're not gonna get 12 unless they are LED

 

If you are thinking of using multiple 13A sockets it gets more complicated. A lot of double 13A sockets only allow 20A in total from both sockets, not the 26A you'd expect.

Some circuits may be tripped at 16A or 20A at the distribution board, so even if you find 2 separate sockets you might not get your 26A. If wired as a "ring" they would normally be tripped at 32A. So you would need to investigate the venue in question to be sure of what would be available and maybe find 2 sockets on different circuits.

[adamharman]

Usually we say 3KW to make it easy ... you're not gonna get 12 unless they are LED

 

On one 13A plug, but you could use two plugs to run 12x 500w lamps.

 

26A total is fine on one 32A ring, but most double sockets won't take it so best to use different ones

[timsabre]

... sorry edited my post to clarify while you were replying

[sleah]

Usually we say 3KW to make it easy ... you're not gonna get 12 unless they are LED

 

On one 13A plug, but you could use two plugs to run 12x 500w lamps.

 

26A total is fine on one 32A ring, but most double sockets won't take it so best to use different ones

Apart from what Tim has said, you also need to consider any other potential load on the ring, such as a high power PA or tea urn.

[adam2]

Yes, about 3,000 watts maximum from a single 13 amp socket.

 

There is no point in "over thinking" this or in arguing over the exact figure because we don't know the actual mains voltage, 217 volts, 230 volts, 240 volts, or 253 volts ? Nor do we always know for what voltage the lamps were manufactured, 220 volts, 230 volts or 240 volts ? And the manufacture of lamps is not that exact, a "500 watt" lamp could be as little as 475 watts or as much as 525 watts.

 

3000 watts probably wont exceed 13 amps, and even if all the above tolerances conspire in the direction of higher current, then the overload will be very small and acceptable for short term or intermittent use.

 

If going near the limit, pay particular attention to the quality of plugs and extension leads, some cheap ones get alarmingly hot at full load.

 

 

 

[timsabre]

Apart from what Tim has said, you also need to consider any other potential load on the ring, such as a high power PA or tea urn.

 

Haha yes, in church hall / village hall type venues the unexpected tea urn can be a show stopper... spent some time a few months ago trying to explain to someone why they couldn't run 3 tea urns off a 4 way extension.

[alistermorton]

If it's incandescent lamps you could safely use 10 300W lamps (PAR56s? You might get away with 12 but that's drifting out of spec) on a single 13A plug, or 12 250W lamps but the light output is going to suffer.

[adam2]

If considering the total loading over a number of socket outlets, then it gets a bit more complex.

 

13 amp sockets are often, but by no means always, on 32 amp circuits. The total load on a number of outlets on the same circuit is therefore limited to about 7,000 watts, but remember that this includes any other loads on the circuit, not just your equipment.

 

A twin socket is normally good for a total of 20 amps, and not 26 amps as might be expected. 3 or more sockets for the full 32 amps in total.

 

Some 13 amp sockets are installed on much smaller circuits, 20 amps or 16 amps, or exceptionally even less.

 

There is also a limit as to the total supply available to the premises, this can be surprisingly small in some buildings. If in doubt enquire.

 

 

 

[Cctheatre]

Thank you!! That’s really helpful - I am using two betpacks in two separate 13amp sockets. Ha Yes the old tea urn - someone actually unplugged one of our beta packs to plug a tea urn in and I swapped them over mid performance!

[Andrew C]

The other question is, "Are they all going to be on at once?" If not, then things get more flexible, but with a risk of someone doing "all up" and tripping the breaker.

[kerry davies]

The correct answer is; "Get an electrician". Knowing what constitutes a safe load is useful but you need to find where the power is coming from and what values of fuse/breaker you are dealing with, especially in an old property. What else is on the circuit is obviously essential to know as is electrical safety and how to check for quality and condition of plugs, leads etc.

 

Without a certain level of basic electrical competence you really shouldn't mess with it especially in venues where the public will be close and you don't know the layout. Just because there is a shiny new twin 13A outlet on the wall does not mean it is wired up with adequate cable or fusing. I have been caught like that more than once.

[adam2]

For anything large, complex or of a heavy loading, I would agree that an electrician should be consulted.

 

However I feel that it is OTT to suggest that an electrician is needed before simply plugging into a standard 13 amp socket a load of up to 3kw. The whole object of the 13 amp socket was that it was to be a nearly universal type into which ordinary persons could plug any appliance already fitted with a matching plug.

 

There is of course a slight chance that the circuit is already heavily loaded, or that the 13 amp socket is on a 6 amp MCB, but that should result in no danger, only a tripped MCB.

 

There is also a chance that the fixed installation is grossly defective, but it is unreasonable to expect that a casual user will pay an electrician to undertake a test and inspection of the fixed installation before plugging in a portable appliance.

 

Do the other users of say a village hall consult an electrician before plugging in a tea urn?

 

I might be inclined to use a basic plug in socket tester before use of a 13 amp socket.

 

 

 

[timsabre]

I agree with Adam, and the very fact the original poster has asked this question shows they have better electrical competence than just the "casual user". The casual user is the one who plugs 4 tea urns into a 4 way extension because there are 4 sockets available on it.

[sandall]

As Andrew C's question suggests - unless it's "everything up at the start & down at the end" you are unlikely to be using all your lamps at once. For mini touring shows I often have eight or ten 500W lights (one or two states, plus a few specials) on a single Betapack plugged into a 13A socket. You just have to work out the maximum current you might draw at any one time.

 

In practise there is some margin for error, as a good-quality 13A fuse will rupture at nearer 20A than 13A (Green Ginger 10A dimmers used to use standard (BS1362) 7A fuses for that very reason). Your real enemy, as others have mentioned, is the 3kW tea-urn, or in winter the fan heaters.