extension leads guide + help

[JohnW2]

If it should become necessary to daisy-chain trailing sockets, then a method of control would be to down-fuse the second socket strip to 10A or 7A, and, (assuming there is a third!) the third to 5A or 3A. This would help act as a control on loading.

I'm not really sure what that would achieve. If the cable is adequate (and given that the current taken by whole lot is limited by the fuse in the first one), then I can't see that it really matters whether high loads are plugged into the first or third one, does it? In general, of course, 'daisy chaining' extension leads is even less 'ideal' than using one!

Please also bear in mind that the socket to be used for daisy chaining is that closest to the cable inlet. This helps avoid high(er) loads having to travel all along the copper inside the trailing sockets.

I suppose that makes sense, although I suspect that the copper conductors within a (decent) extension (between socket outlets) may well have a higher CSA than does the flexible cable.

Kind Regards, John

 

[busterboy]

Also just wondering
I'm planning to run a 10m extension cord to the loft from another room up through some ducting in wall. ( I know what you think but there is no sockets up there and its a last resort instead of souring sockets in loft we rent our home so adding sockets is not an option)

Anyway the lead is to power :
Masthead amp
Slx 6way TV distributar
CCTV DVR


I don't think that the load will be high by using these devices but was wondering if I get a 10m 13amp extension lead can I or would I be able to change the 13amp fuse to a 10amp in the extension lead? The reason for this is I have been reading its safer to use the lower rated fuse that you can get away with as it wud blow quicker with any faults is this true? Wud i get away with just leaving the 13amp fuse ? Just to note this lead will be on all the time to power the devices. Also I think I should get one with surge protection wud this be a better idea?
Thanks

 

[EFLImpudence]

I don't think that the load will be high by using these devices

It will be next to nothing.

but was wondering if I get a 10m 13amp extension lead can I or would I be able to change the 13amp fuse to a 10amp in the extension lead?

You would be able to but there really is no point or 'it doesn't matter'.

The reason for this is I have been reading its safer to use the lower rated fuse that you can get away with

Some do say that but it really doesn't matter.

as it wud blow quicker with any faults is this true?

The fuse is there to protect the cable, not what you put on the end of it.
There is no way that what you are connecting can overload the circuit so as long as the fuse is adequate for the cable 13A or 10A, or even 3A, makes no difference.

The protection therefore is against fault current and/or short circuit current.
As long as the fuse blows before the cable melts or catches fire all is well, the (extremely small) fraction of a second saved doesn't matter.

Wud i get away with just leaving the 13amp fuse ? Just to note this lead will be on all the time to power the devices.

It's not a question of 'getting away with' it.
Do you 'get away with' driving at 30mph?
It is correct.

Also I think I should get one with surge protection wud this be a better idea?

It's not a 'better idea' - it's a separate matter.

It would obviously protect your equipment should a damaging surge occur.

 

[busterboy]

Eflimpudence
Thanks for reply

So on the surge protection matter do you think it wud be a good idea to use a lead with it or just a standard extension lead without it?

Also I will just get one with 13amp plug and fuse and leave it at that as I'm now better minded that it will be safe in loft as the devices in listed are a small load.
Thanks for explaining it better.

 

[JohnW2]

So on the surge protection matter do you think it wud be a good idea to use a lead with it or just a standard extension lead without it?

Many people (including myself) believe that 'surge-protected' extension leads are just a waste of money - but opinions will vary.

Kind Regards, John

 

[busterboy]

John can I ask why you think that surge protected extensions are a waste of money? Are there any benefits of a 10m surge protected extension over a 10m standard one?

 

[JohnW2]

John can I ask why you think that surge protected extensions are a waste of money? Are there any benefits of a 10m surge protected extension over a 10m standard one?

Like many others, I am far from convinced that these 'surge-protected' ones actually achieve anything. Others will disagree, particularly those who wish to sell them to you.

Kind Regards, John

 

[winston1]

You've got the right idea, but we use the nominal supply voltage of 230v for calculation purposes.

So it would be 13 x 230 but other than that, you're doing fine.

Someone might come along and mention power factor but that really only becomes significant on an industrial level, on a domestic level it's usually worth considering.

Much better to use the actual voltage, 240v, than some so called nominal voltage that does not exist.

Anyway I would avoid loading a typical extension block anywhere near 13A. They are not very well made so I would keep it to around 6A. Basically no fan heaters or kettles. Hair dryer only for a short time. TV, DVD, electric blanket, phone and tablet chargers etc are all light loads so are OK.

 

[EFLImpudence]

You've got the right idea, but we use the nominal supply voltage of 230v for calculation purposes.

So it would be 13 x 230 but other than that, you're doing fine.

Someone might come along and mention power factor but that really only becomes significant on an industrial level, on a domestic level it's usually worth considering.

Much better to use the actual voltage, 240v, than some so called nominal voltage that does not exist.

Anyway I would avoid loading a typical extension block anywhere near 13A. They are not very well made so I would keep it to around 6A. Basically no fan heaters or kettles. Hair dryer only for a short time. TV, DVD, electric blanket, phone and tablet chargers etc are all light loads so are OK.

So, with that in mind, in the above example, it would therefore be on the safe side to use 230, wouldn't it?

 

[winston1]

You've got the right idea, but we use the nominal supply voltage of 230v for calculation purposes.

So it would be 13 x 230 but other than that, you're doing fine.

Someone might come along and mention power factor but that really only becomes significant on an industrial level, on a domestic level it's usually worth considering.

Much better to use the actual voltage, 240v, than some so called nominal voltage that does not exist.

Anyway I would avoid loading a typical extension block anywhere near 13A. They are not very well made so I would keep it to around 6A. Basically no fan heaters or kettles. Hair dryer only for a short time. TV, DVD, electric blanket, phone and tablet chargers etc are all light loads so are OK.

So, with that in mind, in the above example, it would therefore be on the safe side to use 230, wouldn't it?

If an item is marked 230v, xW running it on 240V will increase the wattage and current if it is a resistive load such as an electric blanket. If it is a switch mode type device the wattage will remain constant and the current will go down. So at the end of the day there is very little to choose but surely it makes sense to use the actual value of voltage.

 

[EFLImpudence]

But most items aren't marked 230V, xW.
If any are then they, presumably, will be safe at 240 or even 250V albeit using more current.

The point in this case is that the OP is calculating maximum wattage to be used on an mcb.

So if he uses 6A x 230V = 1380W he will err on the side of caution as opposed to 6A x 240V = 1440W.

Just a point of pedantry but it is you who keeps bemoaning the fact that the NOMINAL voltage IS 230V.

When this came into effect relevant values in the regulations were adjusted so that the outcome was exactly the same.
Cable current carrying capacities were not altered supposedly because the extra current could be absorbed by part of the huge safety factor already in the values.

 

[winston1]

Cable current carrying capacities were not altered supposedly because the extra current could be absorbed by part of the huge safety factor already in the values.

Of cause not. The current carrying capacity is the same whatever the voltage. Calling a voltage lower than it actually is will not increase the current. The current will only be increased if equipment is redesigned to operate on 230v. It will be increased even more if this redesigned equipment is then used on 240v.

 

[winston1]

John can I ask why you think that surge protected extensions are a waste of money? Are there any benefits of a 10m surge protected extension over a 10m standard one?

Surge protected extension leads tend to cause nuisance tripping of the RCD. They won't protect against a big surge (lightning strike) and for small surges most equipment is adequately protected anyway.

 

[EFLImpudence]

Of cause not. The current carrying capacity is the same whatever the voltage.

You don't seem to have grasped the difference.

Calling a voltage lower than it actually is will not increase the current.

No, but if you use 230V to calculate the demand then you will be assuming the current is lower than it actually will be.

For example:
A shower quoted at 10kW @ 240V = 41.67A therefore you will require a 45A MCB.
If the manufacturer of your CU does not make 45A MCBs you will have to use a 50A MCB necessitating the installing of 10mm² cable.

However, if you use 230V for the calculations it will be 9.184kW @ 230V = 39.93A so you can use a 40A MCB and 6mm² cable.

My point is that, we hope, the regulation authors realised this and it is therefore acceptable even though nothing has actually changed.

The current will only be increased if equipment is redesigned to operate on 230v. It will be increased even more if this redesigned equipment is then used on 240v.

Equipment doesn't have to be redesigned to run on 230V.
It will just work less well.

 

[busterboy]

Thanks for the surge protection advice.

On the note of the 230 or 240 disagreement lol!

Would I be correct is just using a safe margin for example if its a 13amp extension lead it will be 13 x 230v = total load not to exceed 2990watts or 13 x 240v = total load not to exceed 3120watts.

So to make it easy to understand I could assume a number to act as a safety zone that is less than both of the above numbers. Say 2800watts total load. So i could take any 13amp extension lead and use 2800 watts as its Max load figure. this way I'm lower than both 13 x 230 and 13 x 240 so therefore using 2800watts as my 'do not exceed' figure in theory i cant overload the extension lead using this method and all should be safe enough.

Would this way of thinking be correct and is it practical?
PS. Remember I'm still learning how to work total loads out ect so give me a chance lol!