Posted By Johno
As far as I am concerned, when I see a photo of a 4 gang extension lead with 4 plugs in it and a caption "overloaded sockets" I get rather miffed.

Daisychaining extension leads may be an issue if the length exceeds 15M. When the length is greater than 15M, a RCD must be incorporated into the circuit, either in the D/B, a RCD socket or a RCD plug.

The issues with long extension leads, is not one of overloading but one of increased potential for damage, poor connections, trip hazards and things being spilt into them.

A lead that is heavily loaded >2Kw can have issues with cheap plugs, sockets or just worn sockets. If a plug works lose it can overheat and the fuse will not operate.

If this is an office, you can reduce the hazard by ensuring that they are kept as short as possible, using good quality ones with 1.25mm cable and possibly reducing the plugtop fuse to a 5A or 7A. This will also stop people plugging heaters into them. Remember the 15M rule.

If this is a factory, then RCD sockets or ceeform sockets could be a possibility.

Of course, sufficient sockets in the first place is always best.

Posted By Konstanty Budkiewicz
Andyp,

Previous comments have indicated how to control the immediate situation.

If you own the premises may I suggest that "daisy-chaining" indicates that you have gone through an uncontrolled change to your business plan. Your inferred background concern is the management-of-change. I have previously seen this handled as follows:
Change in operation - temp elect fix using extension leads. Only authorised layouts and designs sponsored by your technician being permitted. Register all such designs and make them subject to maintenance and periodic (3-monthly) review. Long-term changes can then be added to your infrastructure plan where power redistribution needs to be installed in accordance with IEE regulations. If you rent the premises, then your monitoring system needs to be robust.

As an aside, as the weather grows colder and wetter, I suggest that portable electric heaters and kettles are treated in a similar manner for safety, operational and cost reasons.

Kon CMIOSH

Posted By Johno
It would depend on the loading. If it is computers, phones etc I would say it was OK if not desirable.

If you have heavy loads such as washing machines, hoovers, heaters kettles connected, even one, I would agree that it is not especially safe.

With that many, I would probably ensure that the leads are tested and replace the plugtop fuse with a 5 or 7A. The fact that you need so many extension leads may indicate that the fixed electrical installation is rather old. If it is, the main concern from my experience would be the socket on the wall.

Has your fixed wiring had a periodic inspection report made on it?

Posted By Johno
Merv, where did you get this information? It isnt in BS7671?

That statement is part of the French wiring regulations.

Our ring circuits are 30 or 32A and can serve a floor area of 100m2.

Our 30/32A radial circuits can serve a floor area of 75m2

Our 15/20A radial circuits can serve an area of 50m2.

All of these circuits can have an unlimited number of socket outlets.

Posted By Geoff Ferneyhough
What about basic electrical safety? Each Extension cable plug has a 13Amp fuse in it, which means that the four plugs plugged into the lead can total up to a maximum 13Amps.

If you plug more than one extension lead into another the maximun current rating of the appliances cannot exceed the initial 13Amps. With 3 or 4 leads daisychained you would easily exceed the 13Amp maximum and create a fire risk.

Posted By Johno
Geoff, what would happen if you ran 20 amps through a 13A fuse?

Posted By AdrianF
Geoff,
the 13amp fuse would hold

for up to 11hours as I believe

and herin lies the risk of fire

Posted By Johnoo
The fuse would hold for a period of time, dont have the characteristics to hand so cant check. It is designed to operate slowly to prevent nusiance operation.

The 13A fuse will blow before the cable reached a temperature which could start a fire. That is the whole idea of the british standard.

The 15M rule is not rubbish, check the code of practice for in service inspection and testing of portable electrical equipment. It is to ensure that the fuse in the plug will operate fast enough in the event of a fault.

RCDs provide 2 functions, one is to provide additional protection to the wiring the other is for personnel protection where the rating is 30ma or less.

There is still no requirement in BS7671 for RCDs on sockets unless they are likely to be used for equipment outdoors. They are also not apropriate for use on circuits for computers due to the earth leakage.

We have never seen a fire or overheating from properly used extension leads, daisychained or otherwise, we have seen fires from coiled leads.

The fuse will protect the cable always when chosen corectly. The fuse prevents the cable, plugs, sockets from being overloaded. If the fuse did not do this, why do we have it.

Electrical cables are designed to get warm, at least 60C some are rated at 90C and above.

Proper inspection and testing will protect people from electric shock better than a RCD. A RCD is more like PPE and you will still get a shock, just hopefully not a fatal one.

To make it clear, I am not stating that numerous extension leads daisychained is desirable but I am stating that they are not the big fire risk that everyone assumes. The risk of fire comes from poor maintenance resulting in damage to the cables, the same with any appliance.

Posted By Ron Hunter
In addition to the above issues, the practice of daisy-chaining (and loading the circuit with computer/IT equipment) greatly increases the chance of a lethal shock at extranneous metal parts, under an earth fault condition.
This due to the earth leakage currents generated by IT equipment.
Daisy-chaining is not a "conkers bonkers" issue - it is downright dangerous.