Extension lead plug getting warm? advice please?

[John D v2.0]

Simple. 5 + 5 is 10 so your appliance 20 metres away would not reach.

Genius

 

[JohnW2]

The way to test volt drop is to use a loop impedance meter, but that is not something the normal house holder will have ....

Is not the most obvious way to measure voltage drop to use a voltage meter (e.g. a multimeter)?

One could probably only measure the voltage whilst 'running' (the 'start-up' period would probably be too brief), so to know the VD duiring start-up would require knowledge of the start-up current and a little calculation. However, much the same is true if you measured the loop impedance - again, you would still need to know the start-up current to work out VD during start-up.

Kind Regards, John

 

[ban-all-sheds]

So the makers are sure that voltage drop on 20m of 1.5mm² T&E will be OK, but the drop along 5m of 2.5mm² T&E plus 5m of 1.5mm² flex will not be.

How do they know this?

 

[JohnW2]

So the makers are sure that voltage drop on 20m of 1.5mm² T&E will be OK, but the drop along 5m of 2.5mm² T&E plus 5m of 1.5mm² flex will not be. How do they know this?

To be fair, they might be assuming that the fixed wiring has been designed, installed and tested such that the VD at a socket is acceptable (probably within the BS7671 guidance of 5% max) but, since it might be 'only just' acceptable, adding any (unknown) extension might take it 'over the line'. Hence, if VD is as crucial as eric suggests, then that wouldn't be an unreasonable approach.

However, they presumably must (for the UK market) design their product so that it would work with a voltage (at fridge) as low as about 205V (lowest permissible supply voltage minus 5% VD within installation), so the great majority of consumers with supply voltages considerably above the permissible minimum would presumably have no problems related to VD.

Kind Regards, John

 

[blackcloud]

Thanks all, I also have another electrical item and the instructios say "Connect the product to outlet protected by a 16 A fuse" does that mean that I have to ensure the extension cable is atleast a 16 amp? I have never seen a 16 Amp Extension cable, I looked on google but could only find some strange looking plugs like this one

https://www.maplin.co.uk/p/240v-16a-10-metre-mains-extension-lead-a21wu

Anyone got a link to a normal extension lead which is 16amps?

 

[EFLImpudence]

No. Not without having the 16A socket fitted.

Probably just European instructions where they have 16A circuits.

What is the product?
As long as it doesn't require more than 13A, then just a 13A lead and plug will do.

 

[blackcloud]

I need to move my washing machine but there is no socket within reach. I do have a brand new, in great condition, 1 socket 13amp extension lead 240 voltage 1 metre. Is it ok to do this?. I will ensure there are no loops or bends in it and once positioned, it will not be moved and the machine will be the only appliance plugged into it. The appliance is in the kitchen. Any advice will be greatly appreciated.

 

[EFLImpudence]

Yes.

If it's a WM that has a British plug fitted then it will be fine.



If you can wire a plug, then you could get some of these and make the leads the right length.
http://cpc.farnell.com/pro-elec/0138-bk/socket-rubber-1-gang-13a-black/dp/PL09465
Get some 16A or 20A flex.

 

[winston1]

But much better to get a sparks to put a new socket in.

 

[333rocky333]

Simple. 5 + 5 is 10 so your appliance 20 metres away would not reach.

Dont be stupid, the appliance would be 10 metres away

 

[ericmark]

I have only once had major problems with volt drop and refrigeration equipment, this was in Algiers in 1981, the city had at that time a three phase 110 volt supply, I was working for a Dutch company so the AirCons were 220 volt, some one had got there maths wrong and thought 2 phases at 110 volt = 220 volt but in fact it = 190 volt phase to phase so this was rather an extreme case, the AirCons would work, but not for long, and the overloads would burn out.

I actually had to get the boss to read my meter to convince him two phases of 110 volt = 190 volt not 220 volt, I tried the 220 and 380 relationship but could not get them to realise with a three phase system two phase don't equal the sum of the two single phase voltages. I think they got some local supplier who had three phase AirCons in stock in the end.

It is possible other items have failed because of volt drop, however they do work, just not for that long, so it would be hard to say the fault was or was not caused by volt drop under normal use.

As to measuring volt drop, one would need to measure incoming supply and socket at the same time to work it out, and that would be hard, however with a loop impedance meter if incoming is say 0.35Ω and line - neutral at socket in centre of a ring final is 0.94Ω we can calculate the volt drop with a 26A load (20 at centre and 12 even spread) that the volt drop will be 11.5 volt and also know 106 meters of cable has been used. OK the reading can change according to other loads, but we have a good idea if within limits or not.

In real terms if the volt drop is too high maybe the drier will last 1 year and with it within limits maybe 3 years, but one could never really say when it failed this was because the volt drop is too high. So it is a case of doing all reasonable to reduce volt drop, so 1.5mm flex cut to length required without making it a trip hazard. And cross your fingers.

 

[JohnW2]

As to measuring volt drop, one would need to measure incoming supply and socket at the same time to work it out, and that would be hard ...

I think you have maybe missed the point of my last two posts in this thread ...

... voltage drop, per se, is really not particularly relevant - what matters is the on-load voltage at the load, which is very easy to measure. If an appliance is designed work in the UK, then a high VD within the installation of, say, 25V might be a big problem if the incoming supply voltage were, say, 220 (which is permissible), but ought to be no problem if the incoming supply voltage is, say, 250V. Incoming supply voltages obviously do vary, but not usually by much - and if one takes one's measurement at a 'high demand' time of day, it's unlikely that the incoming voltage will ever be appreciably lower than at the time of the measurement.

In any event, if you really want to determine actual VD, then it can again be done easily with a voltmeter if it is possible to switch off any other loads on the final circuit involved, since the voltage measured at the appliance when the appliance is switched off will then, to all intents and purposes, be the incoming supply voltage.

... however with a loop impedance meter if incoming is say 0.35Ω and line - neutral at socket in centre of a ring final is 0.94Ω we can calculate the volt drop with a 26A load (20 at centre and 12 even spread) that the volt drop will be 11.5 volt ...

I'm not quite sure how you get that figure [by my reckoning, 26 x (0.94 - 0.35) is 15.34V, not 11.5V] but, in any event, such a calculation requires knowledge of the external L-N loop impedance. With TN-C-S, it should not be over 0.35Ω (but could be lower), and if it's not TN-C-S, then I think one would probably have to measure it.

Kind Regards, John

 

[ericmark]

One to measure the volt drop with a refrigeration device would need you to record the volts as one is only interested in the volts at start up, once running there is no real problem with volt drop, it is only volt drop at start which is important.

Two there is a correction factor of 0.917 when working out the volt drop for the final ring, so worked out at 16.5197 mV/A/m not 18 hence the slightly different figure, I was not being clever using the correction factor I was being lazy, years ago I was worried if I did an EICR and did not report excessive volt drop could some one in the future claim I was responsible for them not claiming from the installed for circuit to be corrected so instead they would claim from me.

So I built a java script program to work out volt drop and cable length by entering in cable sizes, loop impedance readings and installation method. Idea was it would work on my phone, however once built and tested I realised the volt drop would need to be well out to be sure the installation was faulty, if you consider incoming of 0.35Ω the meter could be out so really 0.33 ~ 0.37Ω the same with reading in centre of ring, can't be sure dead on centre so reading of 0.94Ω could be 0.92 ~ 0.96Ω once one starts to include errors in reading you also get a range of volt drops so only within 15 meters with cable length and +/- 1 volt on the volt drop readings. And this does not include meter error or any slightly high resistance as cables are joined in sockets. So the volt drop would need to be well over the allowance to be sure it was a design error, and not a measuring error or some natural change due to connections within sockets degrading. So unless above the 1.37Ω needed to trip a B32 MCB then not really worth reporting, and I have never seen anyone brought to task after an insulation has been inspected and tested the first time for design faults. So I stopped worrying about volt drop.

If we were required to enter the line - neutral loop impedance or the prospective short circuit current at the mid point of a ring in the test results may be we could be caught out, but it is rare to measure the R1 + R2 once the circuit is in use so unlikely anyone would ever highlight a circuit which has excessive volt drop unless well over the permitted volt drop, even with R1 + R2 there is nothing to say there is actually a socket at the mid point of a ring final so it can't really be used to show excessive volt drop.

 

[JohnW2]

One to measure the volt drop with a refrigeration device would need you to record the volts as one is only interested in the volts at start up, once running there is no real problem with volt drop, it is only volt drop at start which is important.

Indeed, but unless one has fairly sophisticated measuring equipment, one probably has to rely on calculation from knowledge (or an estimate) of the start-up current and the R1+R2, since the start-up current is probably too brief in duration to measure directly with just a meter.

Two there is a correction factor of 0.917 when working out the volt drop for the final ring, so worked out at 16.5197 mV/A/m not 18 hence the slightly different figure ....

'Correction' for what - temperature?

Kind Regards, John

 

[ericmark]

'Correction' for what - temperature?
Kind Regards, John

In a way suppose it is temperature, the it is all to do with cable not being loaded to the max, the calculation was in the appendix of the 17th Edition I remember it used sq root etc, so a bit complex. To do without using excel or java script all set up to do it automatic would be hard, and as with any complex calculation it is easy to make an error, so having it pre-set in java script allows me to test knowing what the results should be, before entering figures where the result is unknown. Sorry not got book to hand and too complex a formula to remember.