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I've set up a workroom in our building site, but because there are walls missing in the basement it's ruddy freezing. So I'm going to burn some energy whilst I work here in the evenings.

I'm about to tell you that I'm breaking every rule in the book, and you're about to tell me to stop behaving like an idiot, and I will say "you're right", but humour me for a bit.

Extension lead runs from a spur directly off a newly installed consumer unit (installed and certified by a good sparky, note: I'm not a sparky, I'm Joe public), with a 16A RCBO (type B). This 5m extension lead has a fuse in that's rated at 13A, but the cable feels a little on the flimsy side. It's an oldish cable. From there I run another 13A 8 way extension lead (2m long). In turn, I run another extension lead (1m long). From there I run a 2kw heater on full, plus another extension lead, fully wound up. From the other extension lead I run a 2kw heater on full, and I keep my hand on the wound-up cable. Sure enough the cable heats up, but it stays on for a good 10 minutes without that cable getting ridiculously hot. Definitely not something you'd leave on, and walk out of the room. But also I can keep my hand on the cable - it's only a bit warm. This cable is a lot thicker, although I guess that doesn't necessarily mean anything.

I then go around and touch all the leads that go back to the mains outlet, and the others (the non-wound ones) are all fine (i.e. no noticeable warmth), with the exception of the older 5m extension lead that feels a bit flimsy.

(Meanwhile, the room is hardly heating up. It barely takes the edge off the cold.)

NB I have 2 types of fire extinguisher to hand, and I'm touch-testing all the cables every 5 minutes. Also, I've now turned off the second heater, because clearly leaving it on will set the house on fire. Finally, I also understand that checking cable temperature is not a reliable means of knowing whether something is safe or not.

My question is this: why the hell has not a single fuse OR the new RCBO for that matter not tripped? 4kw / 240V is over 16A. I can only assume that the heaters aren't actually drawing 2kw each.

Any ideas / advice?

(Save from the obvious "don't plug 2 heaters and stop using extension cables... which I will clearly have to do.)

Do I need to invest in a gas fire?
 
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"Stop behaving like an idiot" just because you expected that.:)
Testing things to the limit is not really a good idea, sudden errors can occur and cause significant problems.
The heaters are probably actually classified as 2kW at 240V to make it sound better but if your supply is 230V then the current drawn by 2 heaters would be 16A.
A 13A fuse will carry 16A almost indefinitely; the current would need to get to at least 22A to go within a reasonable time, several seconds.
A 16A RCBO will not trip at 16A, it would need at least 18A to trip in about one hour of continuous loading.

Build some artificial walls from plastic sheets overlapping to create a smaller and more insulated space within which to work and run one heater on the fully extended extension lead.
 
Notwithstanding the care you said you have taken, you might want to acquaint yourself with what the law says and your own responsibilities under the HASW Act 1974:

Health and Safety at Work etc. Act 1974, Section 7 is up to date with all changes known to be in force on or before 06 November 2017.

7General duties of employees at work.
It shall be the duty of every employee while at work—

(a)to take reasonable care for the health and safety of himself and of other persons who may be affected by his acts or omissions at work; and

(b)as regards any duty or requirement imposed on his employer or any other person by or under any of the relevant statutory provisions, to co-operate with him so far as is necessary to enable that duty or requirement to be performed or complied with.


I think most folk would say you have not abided by 7a and 7b.
 
Quote [ why the hell has not a single fuse OR the new RCBO for that matter not tripped? 4kw / 240V is over 16A. ]

A 13a thermal fuse will not blow at just over 13a !
it take quite a bit more at least 1.5 to 2 times it's
rated capacity is required. Even at 1.5 times
it could still hold for some time.
This is just the way thermal fuses are.
if you want a lower blow threashold ?
Then use breakers not fuses.
 
Come on people. This is a wind up.... or the guy is a complete muppet...
 
I think a gas fire is a good idea. Why are you working in the room in the evenings? Is it your house or do you work there? If you are working why are you not keeping warm with the activity.
 
Sadly it's not a wind-up. I'm working in a room above a basement with no walls on. Freezing air flows freely from below, up the chimney which is open from below, and into the enormous fireplace which is open, and up again three storeys. Trying to type on a computer in a 5 degree chill for a few hours is no wind-up.

(@Vortigern - my work is not active - I've set up a computer screen and using it as a temporary office)

As mentioned I'm a layman, genuinely wanted to know why a 13A fuse could take more than 13A - thanks for explaining, I understand now. Also I think the best hint so far was putting plastic on all the walls, anything to prevent the draft. There's an enormous open hath with flue that goes up 4 storeys and a flue that goes down to the fire below (i.e. basement room with free flowing freezing air) The space is brick and concrete, temporary power supply.

Having a fire extinguisher to hand (i.e. with intent) is not as ridiculous as it sounds, when you're working on a building site where builders regularly do ridiculous things like using a power breaker to remove sections of wall without checking there isn't live mains running through metal capping in the wall and a socket on the other side. (Yes really.) Or, my personal favourite, complaining that every time they touch the metal frame of a workshop they get an electric shock, even when their barrow touches it. (Yes, I had an electrician come round immediately, I ordered workers to get out of the space. I came back later to find them in there working again.)

In the last 2 years of developing my own home using contractors I've seen it all.

Only 3 weeks ago we had our mains upgraded to 3 phase. I was doing stuff out the front and watched the guy (subcontractor of a company working for SSE) put his spade through the incoming cable. Loud bang, a lot of smoke, and the bloke went white. Saw the whole lot myself. He put a cone over it and called SSE who came out within 25 minutes...

You guys should get out more - that's what a lot of groundworkers are like. Health and safety in the industry (maybe I should say "sections of the industry") is a bit of a joke. Sadly I'm not joking when I say that I've bought eye and ear protection and try and get guys to wear the stuff, and they refuse. I think you all may be used to working with other first and second fix contractors if you haven't been exposed to this kind of stuff before!

p.s. fire extinguisher was my insistence. As were the temporary fire alarms. I'm living in the flat above....

Anyway back to my own muppetry, not that of my deviant groundworkers. The reason you don't plug a big load into an extension lead that is wound-up is overheating, I wanted to know by how much and how quickly. But I take the point, the socket might burn before the wire.

Looks like I have a lot of chipboard to put on walls / fireplace and gaffer tape to run around the tops and bottoms of the room! And I may need a gas fire.
 
fantastic post its made my day .. don't get too cold hayzmat and keep those hand nice and warm on that cable reel !

Please finish it off for me..... , are the fire extinguisher water based by any chance ? that would be the best one's to use, but of course your know that ;)
 
We do get a few wind ups here and sometimes it's hard to tell the difference between genuine muppetry and educated wind ups. :)

Any thoughts of using the extension reel as a form of supplementary heating should be discarded. :D

The outside might be warm but the centre will be producing heat faster than the heat can dissipate leading to........

get yerself a wooly hat and gloves. :)
 
I came down yesterday evening with one of those large hats that goes over your ears and velcros under your chin. And a massive blanket. Unfortunately I can't do my work (hours and hours of photo editing) with gloves on and therein lies the problem!

Just to reassure @Upton Sparks, the fire extinguishers are those large blue canisters that you see on campsites. They are supposed to put out electrical fires, right? :p

Seriously though, I do actually always forget which extinguisher is which, but luckily they say in very clear writing on the sides what you can and can't use it for. Gladly I've never had to use one in my life.

I think I might have to start plugging gaps and putting up plywood walls and taping around the edges... and only using one heater *sigh*
 
Wondering if a tent would help .
(but they are pretty flammable )
..Swift exit posible with a knife !
Cautiously touch plug tops - see how hot they run .
(will not be long - before fuse holder starts to discolour)
Damage will occur at weakest point's ...
just hoping none of them are anywhere important / unsupevised !
 

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