Moulded-on 13A plugs going bad

[Dave Plowman (News)]

Can't you just change it yourself? They're hardly expensive enough to quibble over who pays. Unless getting a man in to do it.

[Roland Perry]

In message , at 11:24:05 on Fri, 3 Nov

2017, "Dave Plowman (News)" remarked:

On one hand I'm no longer on site (my visit was by necessity quite short, originally asked just to change a fuse by a friend); on the other hand I'm not inclined to start messing with a landlord's ring main electrical fittings (even if I *will* wire a replacement plug on a tenant's appliance).

[Roland Perry]

In message , at 11:24:05 on Fri, 3 Nov

2017, "Dave Plowman (News)" remarked:

The landlord is a sufficiently large organisation they have their own in-house handymen.

What I don't know is where they draw the line between that they feel obliged to fix as part of the maintenance/management contract, versus things they allege the tenant has broken.

On a quite separate matter, I've had a dispute with a landlord in the past about the responsibility for replacing a toilet seat where the hinges broke through years of un-mitigated corrosion.

It seems pretty clear they have a statutory duty to fix any faults with the basic sanitaryware functionality, but does that include the seat? Or moving the goalposts slightly, what if it were a lid above the seat.

Their approach to "fixing" a gas fire in the lounge which had been declared unsafe by a gas inspection, was to simply attach a "do not use" label, for example.

[Dave W]

Yes sorry, true enough, but how "dramatically"?

300k at 240V is bad enough, producing almost 250mW of heat.

[tabbypurr]

Once a plug has overheated badly the socket is ruined, contact springiness gone. So even in the unlikely event of it not being fried yet, it soon will be. Always replace it, unless you like fires.

NT

[Dave Plowman (News)]

Likely still charged out at some silly amount. ;-)

Sometimes it's easier just to change somethings as simple as a socket yourself. Assuming you have the necessary skills.

I suppose it might depend on careless use of a corrosive toilet cleaner?

Even more reason to replace the socket yourself. Given how cheap they are

- a gas fire is a different matter.

[tabbypurr]

Dramatically.

NT

[Roland Perry]

In message , at 14:44:54 on Fri, 3 Nov

2017, "Dave Plowman (News)" remarked:

But where is the line in the sand? Is fixing the seat, regardless, a statutory duty for the landlord?

Different landlord. And I didn't have the time or materials to do a replacement on the spot.

[Dave Plowman (News)]

You don't need to guess. Just plug in a 3kW fan heater on full and check.

[Roland Perry]

In message , at 15:12:58 on Fri, 3 Nov

2017, "Dave Plowman (News)" remarked:

Assuming you have one handy! I don't even have an electric kettle at home (I use a traditional one on the gas hob).

[Johnny B Good]

Resistors have both a maximum wattage and/or voltage rating. The voltage rating is usually redundant for low value resistors since, for example, a

10 ohm 3 watt resistor would be burnt out in rather short order with 30v applied (30x30/10=90 watts). Even a mere 20v would generate some 40 watts' worth of heat, way in excess of its 3W rating.

Higher values such as 300K are voltage limited even if rated to 1 watt or more. The voltage rating with most quarter and half watt resistors could be anywhere from 100 to 300 volts depending on its composition. High value resistors are available with Kilovolt ratings but these are specially designed to cope with high voltage by virtue of their much longer body length.

The common practice is to use 2 or 3 resistors in series to make up the required value and wattage rating where the potential difference across the string is almost or in excess of the voltage rating of the individual resistors, especially if subjected to dissipation close to their wattage limits. The half watt 220K resistor used in the classic neon lamp mains tester may only be rated for 250 or 300 volts but, allowing for the 60v running voltage drop (90 volts or so striking voltage), the resistor only has to dissipate around 150mW and withstand about 180 volts at most (such as the user standing bare footed on a wet concrete floor and using a sweaty finger tip to contact the 'earthy' end cap of the tester).

A carbonised track inside a mains plugtop, although only measuring some

300k using a typical multimeter (typical test voltage being 15v on the high resistance ranges) will measure rather lower using a 500v megger since the carbonised track will warm up and be subjected to voltage breakdown with induces arcing (a negative impedance effect) which rapidly increases voltage stress elsewhere until the whole of the carbonised track is consumed by the arc, hence the "dramatic failure" on application of, in this case, full mains voltage (peaking at some 350 volts every 10ms on a 50Hz supply) versus the apparently inconsequential 300K leakage path registered by a typical multimeter using no more than a test voltage of 15 volts.

Resistors, especially carbonised tracks, will only follow Ohm's Law so far before they start to follow a law mediated by the negative impedance characteristics of arc conduction due to exceeding their breakdown voltage limit. The switch from positive to negative impedance is swift and dramatic.

In the case of an actual resistor component, the resistor will usually fail like a fuse in most circuits. However, a resistor created out of carbonised plastic can use the remaining untouched plastic as 'feedstock' to make a wider conduction path capable of blowing the plugtop fuse, possibly even starting a fire in some situations.

If you can get a leakage resistance reading between the pins of a 13 amp plugtop (whilst not attached to the appliance cord) using a general purpose multimeter, that plug should be scrapped immediately and a new plugtop fitted to the cord.

[Roland Perry]

In message , at 16:10:31 on Fri, 3 Nov

2017, Johnny B Good remarked:

Using a second meter to measure the voltage applied by my first meter when checking resistance, it's 1.5 volts.

Which is what I did, and it fixed the RCD tripping.

[Johnny B Good]

It tends to be poor contact due to tired spring contacts in the socket rather than arcing in the plugtop that causes the damage. One of the things to be mindful of is the plug 'walking out' of the socket due to thermal cycling effects on heavy wattage appliances such as 3KW electric kettles that sit on a permanently plugged in base which are particularly prone to this effect due the frequent cycling of use through each day's use.

It takes several months before a half millimetre gap becomes evident with our own 3KW kettle. There's no fixed rule of thumb in regard of frequency of checking other than to use the MK1 eyeball and, if in any doubt, to firmly press the plugtop into its socket every so often. It

*really is* just a matter of being mindful of the potential problem and making sure the plugtops remain fully inserted into their sockets.

[tabbypurr]

NT:

afaik no-one suggested guessing

great, an unsafe work method that either way will produce an unsafe result. At least I know why he's in the killfile.

NT

[ARW]

But you did not dissect the plug afterwards with photos:-(

That would have made good viewing.

[John Rumm]

On the principle of preventing a dangerous situation arising, yes.

I would also advise the tenant to contact the landlord and advise them of what has been done so that they have the opportunity to inspect and test as required if they so want.

[Roland Perry]

In message , at

19:54:52 on Fri, 3 Nov 2017, John Rumm remarked:

I'm not sure most landlords would agree with amateur repairs of this kind (or do you have some professional qualification, in which case it's somewhat of an outlier).

[John Rumm]

If there was a risk to the person living there unless then repair was done, then personally I would not be particularly concerned what the landlord thinks. They can hardly argue it would be better to leave the property in an unsafe condition.

Obviously circumstances will dictate how critical the repair was. If it was a socket that could simply be abandoned and another one used instead

- then it would be better to do that and stick a note over the socket. Then ask the landlord to get it fixed in due course. If however it was (for example) the only socket capable of feeding a important bit of kit (CH boiler, immersion, washing machine etc) then it would better IMHO to get it fixed there and then.

(whether you fix it yourself, or call an emergency electrician is another matter)

What like a GCSE in socket fitting? ;-)

No, although I expect my domestic electrics skills would stack up fairly well against those of many landlords.

[Dave Plowman (News)]

How do you class an amateur repair? The repair being done to a poor standard? That isn't an amateur repair but a bodge.

Would replacing a faulty light bulb with a new one of the right type be better done by a pro? Would it then work better than if done yourself?

However, I'd certainly not suggest you replace a socket if you think that a task which requires a pro. And not sure you should have replaced that plug either, since doing an 'amateur' job on that can be a safety hazard too.

[RJH]

It's that kind of thinking that can inhibit any manner of involvement in getting stuff done.

I have a mate (2 degrees, 1 in (materials) engineering) who wouldn't change a fuse in a plug because he believes it's borderline illegal, and the domain of qualified electricians.