Melted socket

[Jhcp1977]

Hi can simeone give me advice I had a electricia install a outside socket that has melted the plug before I ring him can someone tell me if it's been installed correctly? I can't find the makes anywhere online are they inferior products?
I am not happy as my daughter was in the hot tub at the time so shouldn't have something tripped in the house or the RCD on the lazyspa ? As with it all being melted it was still working it's only because she could smell burning I was alerted to it ?
So from what I can see the middle switch is what it's connected to with a single cable running to a outside weatherproof socket any help appreciated

 

[telectrix]

tub.not tun.

 

[Julie.]

Thank you all speaking to a different electrician I explained that's there's a single 2.5 twin and earth run straight from a outside socket to a 32amp MCB and he said that's not right any way I will wait and see but what's your opinions on that correct or not

As long as that cable is supplying only the one double socket outlet, it is technically OK, as the fuses prevent an overload to the cable, though instinctively people would expect to use a 16 or 20A MCB on that circuit.

The issue you had/have is nothing to do with the fixed wiring, and everything to do with the plug and fuse within it.

The fixed installation cannot detect when something connected externally to it gets hot - it could be a toaster (which is OK getting hot), or it could be a loose connection in the plug or poor quality plug/fuse (which would be a problem).

I would suggest either the plug/fuse is not of proper quality, or a connection was loose.

Could you post additional photos of the plug, especially the pins and markings on the pin face?

 

[telectrix]

deffo the fuse/holder contact in the plug.. looking at the socket faceplate, the scorch mark is directly under the plug fuse.

 

[Jhcp1977]

that's a 10mA RCD factory fitted in the tun lead.
as for the 2.5mm cable from a 32A MCB, is that cable direct from the MCB or is it a spur off a socket in the house? if it's spurred off a socket on a ring final, as long as it's the only socket on the spur, it's compliant.

It's 2.5 From outside socket no spurs nothing just that one socket on its own mcb

 

[telectrix]

It's 2.5 From outside socket no spurs nothing just that one socket on its own mcb

ideally it should be on a 20A MCB as loads in addition to the tub may be plugged in, so it's not a fixed load. not a big job to swap out.

 

[marconi]

Ask the electrician to fit another plug. Then ask him to measure the current when the spa is in heat mode and then measure current when in heat and bubble mode. You need to confirm that the current is no more than 2050/240 Amps and 1850/240 Amps respectively. Meanwhile I will look up spec and call company. The failure is over current and thence overheating of fuse . This plug socket combination is suitable for no more than constant 10amps because the plastic and rubber construction makes it very difficult to dissipate heat especially generated in the fuse.

 

[marconi]

https://images-eu.ssl-images-amazon.com/images/I/F1cu1b3il5S.pdf

see page 10. The maximum power may well be 2050 + 800 + 50 = 2850 Watts for heater, turbo and pump unless the controller switches off parts of heater when turbo turned on. You need the measurements of current drawn in all the spas modes of operation.

As before a 13Amp plug socket in plastic and rubber with lid of socket closed will fail on overheat if over 10A drawn for more than 30 minutes. The heating effect of the current is a quadratic function ie heat produced is proportional/varies as current x current or current squared. Thus heating effect at 12A is 1.44 times greater than at 10A ie 12 x 12/(10 x 10) - At 13Amps it is 1.69 more than at 10Amps. Typically the fuse and its holder will produce a few watts of heat at rated current which if it is not conducted away will cause considerable increase in material temperature and thence thermal damage as one can see from the photos.

 

[marconi]

I have submitted a technical query on line and will update once I have a response. Meanwhile I have just come off the phone with lazy spa uk support desk who confirm the maximum power consumption of your spa is 2050 Watts so about 8Amps. Time to call the sparks back to measure those currents. If they do not exceed 8Amps or thereabouts then it points to the inadequacy of or fault with the socket plug combo and/or its standard of installation. If more than 10A then I would suspect a fault with spa itself causing excessive over current and overheating as described earlier which you should report and pursue with supplier or lazy spa uk.

 

[marconi]

Studying the plug and a similar one on our kettle ( 2.5kW) in attached photos - the region of most intense heating seems to be along an axis through two points; the middle of the fuse and the rivet joint of the line terminal - upper fuse clip assembly. These two points are both high current density and thus high Joule heating. Permaplugs use bussmann fuses so of good quality. The live plug pins and socket entries show no sign of overheating. Telltale signs to ponder on.

 

[marconi]

I reckon it would not have been much longer before carbonisation of the plastic former between the plug earth pin and top fuse clip precipitated a line earth tracking current which would be detected by the supply side rcd turning off the power.

My learned EF colleagues may wish to advise the OP on specific questions to ask and confirm with the sparks before he visits since this is an IET special location and installation (GN7 IIRC).

 

[littlespark]

You must have had a quiet afternoon, @marconi ? Im sure all the pubs are open now if you're at a loose end

 

[marconi]

You must have had a quiet afternoon, @marconi ? Im sure all the pubs are open now if you're at a loose end

Waiting for the snooker to start......more seriously I have been baby sitting 9 week old jack russell, Maud, with a chronic itchy skin rash - quite upsetting to see her regularly scratch herself, only relieved when asleep or stroked - half way through treatment as advised by vet. Up at 5am because she was so troubled by it. Wife in hospital. was due home Friday but learned for good reason now Tuesday earliest. So needed occupying. Could not go in my man shed to dabble with some electronics ’cos being painted by two fine fellows , father and son, both with Asperger, who to my great shame tested my patience for reasons which are my failure not theirs. So needed distracting. Enough said for somewhat ‘grandstanding’ on this .......

 

[ruston]

Waiting for the snooker to start......more seriously I have been baby sitting 9 week old jack russell, Maud, with a chronic itchy skin rash - quite upsetting to see her regularly scratch herself, only relieved when asleep or stroked - half way through treatment as advised by vet. Up at 5am because she was so troubled by it. Wife in hospital. was due home Friday but learned for good reason now Tuesday earliest. So needed occupying. Could not go in my man shed to dabble with some electronics ’cos being painted by two fine fellows , father and son, both with Asperger, who to my great shame tested my patience for reasons which are my failure not theirs. So needed distracting. Enough said for somewhat ‘grandstanding’ on this .......

It all comes together doesn't it. I hope everything works out well for you.
You are a kind man.

 

[DPG]

I often wish Marconi was a neighbour of mine.

 

[ruston]

There are a lot of kind people on this forum who give their time up to help others.
You can ask no more than that from anyone.