Went to check on grow room and found no electricity was coming from the socket. Hadn't checked room for 3 days so not sure how long had been out for. Anyways, I found the problem, the neutral pin of the plug had exploded / melted. The outside of the plug close to the pin was darkened, the pin itself had had the black material close to the base of the plug melted away. The wall socket was darkened heavily around that pin, and when i took the front face off was burnt up pretty bad.

The room is in the loft, which just has one plug socket. A 13amp 4 way extension comes from the single socket. Into this 4 way, goes the 2 plugs for the contacter running the lights (3x600w lumatek ballasts). There is another 4 way coming off the 4way which has 2x12" desk fans, and 2x160l ruck fans.

I thought a 13amp fuse was good for just over 3000w? None of the cable is coiled up it does loop back on itself, but have it straightened as much as possible.

Any idea on what could have caused the plug to blown?

Can't confirm/deny that but i'm interested also, i've got my whole grow running off a double wall socket, which can't be good

you've overloaded your circuit & your bloody lucky it didnt start a fire

3x600w lights coming on together will cause a huge surge and it's over-loaded the plug. As arai said, you've been lucky it's only melted the pin of the plug...

put a seperate 40amp RCB supply on a 10mm cable to your loft n you can run prity much what you like, cost you 150 qwid for the gear n you cud add the rest ov ya house on it n make that safe n all !!!!!!!!!!!!

we had them same symptoms in our conservatory at home. we had freezer,tumble drier,heater,pc all plugged into one single socket. one day got home and the plug was all blackened/scorched up bad and there was a kind of fishy smell.. glad it didnt cause a fire for you or me!!

i'd say it's almost certainly due to a bad connection in the plug, and not overloading, the fuse would pop long before the cable melted from overloading.... bad connections on the other hand.....

a bad connection creates resistance, current times resistance = volt drop... volt drop times current = power.... power equals heat, heat equals bad!!

good solid connections should offer no resistance, although copper wire does have a very small resistance, which is why you can only have so much current going through it, and the larger the wire the more current it can handle, if a connection is made badly, ie the strands are badly frayed or whatever, then the area is smaller and the wire can handle less current, this is why these sorts of things always happen at plug terminals and connection points

and as you're using electronic ballasts, the start up current from 3 x 600's shouldn't be a problem at all.

1.5mm wire that most 4 ways are wired with can handle around 16A, although you are running very close to the current limit for the fuse with all that equipment, generally it's accepted that for continuous use circuits should be run at around 80% of full load. ignore wattages of your equipment, as these are misleading, current rating is what matters, you lamps i imagine run at around 3A each? so there's 9 amps gone, and your fans run at around an amp each? so that's 11A ish, add an amp on for a bit of a safety margin and your pretty much right on the limit for the fues, but still this should be fine, the next size cable down is 1.0mm and this is only rated for 10A so if your extensions are rated at 13A then they'll have 1.5mm cable which is perfectly fine for 12-13A.

Although it has been said below, the wattage doesn't matter, use the amps. I have a plug socket in front of me that says "13amp -Don't exceed 3250w".


I replaced the single socket, with a double socket plug. Is this any safer than having a single plug socket with a 4 way in?

A friend has recommended a circuit breaker, obviously this would improve saftey, does it reduce the fire risk significantly?

a double socket may actually be more dangerous than a 4way extension lead, depending on the wire that originally fed the singe socket.

a 4way extension lead will have a 13A fuse in the plug, and the 4way itself will be able to carry 16A on it's cable, meaning it should in theory never go within 3A of it's maximum load. providing all the connections are good.

if you change from a single socket to a double socket on your wall though, you can now pull 26A (two plugs with 13A fuses in) through the wire feeding the sockets, whereas before with a single socket the most you could have would be 13A, if the cable supplying the socket was only ever meant for a maximum of 13A, then you can see the problem here!

of course most likely, you'll never get anywhere near 26A! but the potential is still there

This is a very scary thought Sharkjazz !! I hope you find the source of the problem...although im sure a re-wire should sort things as the knowledgable ones seem to think it was a loose connection...?
Im sorry to jump in here SJ, but im just doing the wiring for my loft...and have no idea wot im doing!
So wondered if anyone could tell me, i have a FAT cable going from the consumer unit (through the 30amp sockets fuse) right up to the loft.
Can i just wire a socket onto this? Or am i going to burn my house down??
Good luck Sharkjazz
Strain47

Strain47 - if you have no idea what your doing, then stop before you electrecute yourself !

you've got 2 options, you can get a electrician in to do the work for you but bear in mind they might discover what your upto
hopefully you might know someone who you can trust ?

or you can do some reading on the net & learn to do it yourself, you can start here , here & here

Cheers Arai, i neede someone to stop me...
I have wired the cable up correctly, and i managed to blow a 30amp fuse by shorting it...im a prat.
I will have a read as im not stupid, just wondered if i was going to burn my house down by fitting my sockets on the end of this cable?
Strain47

Lucky you didn't incinerate your house dude!!.....if your changing a single to a double make sure the feed cable is up to the job fella.....general rule for all those who don't know owt about electrics is - get a pro in DIY in this game can kill you quite easily...if your your worried about plug in extentions just make sure they have the wiring to handle more than the fuse rating and use a plug in RCD (30mA) is good, anything more sensitive will just piss you off.

When designing electrical circuits the standard practice to allow for inductive loads (ballasts, fans & pumps) is to multiply by 1.8 to allow for the maximum current that may be drawn by the equipment. This is a good guide to use but it is only true for ambient temperatures upto 30 degrees. So for 3 600w hids alone the circuit must be capable of handling a minimum of 3240 watts which 1 socket does not. I hope you get your problem sorted quickly and take some of the advice here and get someone in to look at it and retest the heat damaged cable to insure its current carrying capacity has not been compromised.

that's only for inductive loads with unkown current ratings... ballasts have corrected power factors anyway, and secondly they have a current rating printed on them... thirdly this guy is using electronic ballasts which are dam close current wise to a resistive load anyway. i'll bet my left testicle it's due to a bad connection, i see it all the time. also the socket is protected by the 13A fuse in the plug, it's not actually the socket that needs protecting anyway, it's the wires supplying it, which will be 2.5mm and capable of supplying over 20A. the cable in the plug and extension lead is rated up to 16A. doubt this is an overload fault. agree though, the cable will be a bit knacked, but only at the joint, just cut the cable back to clean copper and rewire the plug

Getting a pro in just isn't an option, the plug socket is in the attic, next to a ramshackle "room" I have built. So without taking it all to bits, the game would be up straight away. Don't have any sparky mates either.

I'll check those links out, cheers.


To the people who said a double socket is more dangerous, can you explain further. As long as I don't plug anything more in, would it be more dangerous? Having everything go through one 4 way, isn't that more dangerous as it is alot through one plug. Now it is split into two plugs, so each is getting half of what the one plug was getting.

Have attached an image of the socket / electricity layout.

I have purchased one of these RCD safety adaptors from b&q, should i plug in for the mains plug of the contacter? Or the four way that feeds the timer plug and fans?


Another post mentioned that perhaps the cable feeding the socket can't take a double socket, the socket is on the house sockets circuit. The actual cable is a flat cable 10mm width, 5mm height. Can you tell from looking at the cable what it is capable of, or does it need a testing kit? If so, what kind of kit is required?

What would be the usual amout of copper to cut back before rewiring the plug, I cut the burnt bits off the neutraal wire as this was pretty bad, but the other wires looked fine. I think I will go cut an extra few cm off just to make sure.

i think the trouble is that a single socket has wire leading up to it that is capable of taking a certain load. if the socket was installed with the wire for a double, triple or more, then the electritian would increase the size of the wiring accordingly. just putting a double socket on original wiring may over load the wire. its designed for 13amp, therefor running everything off of the one socket with a 13amp plug to start would restrict the user to safe laods, otherwise the fuse will blow. i run my whole 600w grow, 2 fans, dehumidifier, 2 tube heaters and 2 oscilatting fans plus 40w lamp and hi fi off of one socket, but have my whole grow going through an rcd and surge protected line using plugs from homebase. nothings gone wrong yet, although i was suprized at your loading, its put mine into comparison a safe load. hope things get sorted. i also have a 30amp energy saver plugged in, ebay waste of cash i imagine but i had a spare socket left over

put a fused spur unit where your single socket is, then from this connect to a double socket, then even if the wire is only capable of feeding a single socket, you can never overload it by plugging in two lots of 13A because the fuse in the spur will blow. cut back until when you strip the insulation on the inner cores you see shiny copper

that made me laugh mate..

glad i had a look at this thread as i have been meaning to upgrade from 4 600w to 5 600w lights,

i am running the lights of a 4 way extention on a double socket aswell, the other plug on the same double socket power's my in/out, oscillating fans, and pumps etc scraglor am i bad ? what can i do to make it safer before i add the extra light next week,

looking to get that rcd you recommended but i suspect thats not gonna cut it ?

e2a , sorry for crashing the thread

an rcd only trips out when there is a fault tp earth, it's a last resort protection and trips out when the damage is done. it doesn't protect against too much current (thermal overload) which is what does the actual damage, i.e. causes heat, this is what a fuse is for. a fuse however may take a long time to blow if the overload is small, and if you have any bad connections then these may heat up to fire point before the fuse blows, which is why good connections are so important.

4 600's from one socket is really pushing it! i'd run to from each socket and spread the load equally between two sockets, also do you know if the socket is on the main ring or a spur? (if it's on the ring then it will have two reds, two blacks and to earths powering the socket a spur has one of each colour) personally i think 2400watts is enough! but you could get away with another 600, 3 on one socket 2 on the other. but i'd check all the socket connections and extension lead connections, 5 x 600's is about 20A (which is about 60A of start up current!! so also stagger the time between the lights as they start up)

When dealing with electricity make sure you know what you are doing. The problem could have been any of the sugestions before so best to start from the begining and cheack it all over and allways have spare fuse at hand hope you sort it anyway

thanks for the advice mate,

i take it by running of the other socket i would need a seperate relay aswell ?

i suppose that would mean 2 clicks instead of 1 when relay's flicks on and of , maybe i'm paro but i hate the clicks , but if its got to be done

i'll check tomorrow to see if it's on main ring or spur. luckily i'm chopping tomorrow so i'll be able to unscrew faceplate when lights are off,

if spreading the load could it manage 3 lights on each socket ?

you can do, but as the thread shows, make sure everything is well connected. the sockets and plugs are rated to take that kind of current, but if there are any weak points in the system (bad connections) then they're much more likely to show up under that kind of strain (ie burn out)

You should google "ring main" and also "spur" to see the differences and the wise way to cable up your kit.