Rank: Super forum user 
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I'm currently putting a small presentation together on eletrical safety in the workplace (office/retail/small warehouse). I have to do these presentations regularly and picked this subject having recently found a 4-way extension lead with three appliances attached and double plug with two appliances attached in the 4th socket. Now obviously that doesn't make for much of a presentation so I've considered a bit on wind-up extension leads and daisy chaining 4-ways. I know we all look in horror at the sight of daisy chained 4-ways but what exactly is the risk (apart from the trip hazard)?
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Rank: Super forum user 
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One risk is that you very quickly lose sight of the total load. It can get to the point where the combined load is a multiple of the current that was intended. Since fuses will happily carry 2 to 3 times their rated current, there is considerable risk of fire.
You can also lose sight of where to turn things off. The place where you turn something off should be clear and easy to reach. If you have created a spaghetti junction of extension leads it can get extremely difficult to decipher what comes from what socket.
Jane
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Rank: Super forum user 
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Getting a bit technical, but this arrangement also increases the earth fault loop impedance making it less likely that the protective fuse will blow should there be an earth fault, again increasing the risk of fire.
Alan
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Rank: Super forum user
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Wow!
I have just graduated to being a Forum user...
Must get a life!!!
A
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Rank: Super forum user
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ahoskins wrote:Getting a bit technical, but this arrangement also increases the earth fault loop impedance making it less likely that the protective fuse will blow should there be an earth fault, again increasing the risk of fire.
Alan Hi Alan, Whilst your 'getting a life'...pick one for me;-) I understand the bit about increasing the impeadence but how would daisy chaining do that?
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Rank: Super forum user
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The increased length of the conductors and the resistance at each connection (both at the live pin/socket and the earth pin/socket).
Not a large increase perhaps, but that would depend on the lengths and the condition of each socket.
Quite often these units are cheaply made and af quite poor quality.
A
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Rank: Super forum user
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ahoskins wrote:The increased length of the conductors and the resistance at each connection (both at the live pin/socket and the earth pin/socket).
Not a large increase perhaps, but that would depend on the lengths and the condition of each socket.
Quite often these units are cheaply made and af quite poor quality.
A
Ok. so to use a really a bad analogy; each extra connection will back up the traffic like an extra set of badly timed traffic lights until such time as the traffic decides to take an easier route? John
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Rank: Super forum user
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The impedance (liken it to resistance) is from the supply source back to the earthed neutral point, so any increase in resistance in the circuit due to poor connections will increase that and limit the amount of current that will flow through the fuses under fault conditions. I would thnink that the plug fuse in the first adaptor (plugged into the wall socket) would likely be the most affected and therefore less likely to blow.
Please note that I have no formal electrical qualification, but I have studied the subject. If I am wrong or have explained it badly I expect an 'expert' will soon put me straight!
Might be a long wait though, as we don't appear to have so much activity at the moment...
Alan
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Rank: Super forum user 
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Did not pick this up till now in replying to another thread which linked back to this one.
The new forums are teking a bit of getting used to, especially as the remeber me bit don't work for me!
Generally all the above!
Put simply, impedance is the a.c. equivalent of d.c. resistance.
Don't worry about the difference for what we are talking about here it only really becomes an issue with big distribution cables, like those run to fuse boxes and by the regional electricity companies.
The likelyhood of overheating these short runs of cable due to overloading is doubtful, HOWEVER, not impossible, and a 13A fuse can carry up to 90A before it blows!
But, not for long, at 95A it should blow in 0.4 sec.
I have written a longer response to the other similar thread.
I could go on for days on this as electrical safety is my bugbear, as my background is in engineering!
MY biggest gripe with this electrically is the increase in earth fault loop impedance.
This increases the risk of shocks due to the fuses/circuit breakers "protective devices" not operating and allowing the fault voltage to remain on the appliance.
Paul.
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Rank: Super forum user
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Hi Paul,
Just read your post on the other thread and think I've got it. In summary; The more 4-gangs that are daisy chained, the greater the risk that a person will provide the path of least resistance in the event of a fault!
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Rank: Super forum user 
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Is that it in a nut shell?
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Rank: Super forum user
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