Plug pin getting warm

adsmith · May 23, 2022

Hi guys

Recently I've had a wall paper steamer plugged into my upstairs ring main and noticed after several minutes a fishy smell which was the result of a burnt out live pin in the socket. To add add main breaker did not trip at this point or even the plugs 13amp fuse (could you advise as to why?)

Assuming it was either a faulty plug or socket I replaced both. (Socket connections where fine)

I've since tried the steamer again for a few minutes, removed the plug and the pin was warm/hot

Unsure if it was the upstairs ring main issue I tried it on the downstairs ring main and same problem.

I assume now this issue lies with the appliance but I'm unsure as to what is causing it and wonder if you guys could give me some knowledge. I assumed something to do with current draw.

Thanks

marconi · May 25, 2022

Re LN's #15: Thank you for such a thorough reply. You always go the extra mile.

Folk may not know but fuses themselves have a maximum power dissipation at their rated current. For BS1362 fuses it is 1Watt. This heat has to be dissipated somewhere and somehow. The Bussman specification for their BS1362 says 1000hours operation at 13A. I was taught the 2/3 or 3/4 current rule for a fuse which when applied to a 13A fuse is 10Amps maximum (3/4 x 13 = 9.75A). At 10A fuse power dissipation is (3/4)squared = 9/16 or just over half a Watt - about 50% lower than at 13A.

https://docs.rs-online.com/9819/0900766b8002b71e.pdf

I reckon that one should only use MK bakelite/pottery plugs for long duration 13A loads and not the MK toughplug because its plastic cover acts like a thermal blanket. All other plugs than MK bakelite/pottery are only good for up to 10A at best. That less capable plugs are often used on 10-13A loads is mainly because the duty ratio = average current to rated current is lower than 100% during the period the current is flowing so the 1W heating effect does not have time to cause thermal damage.

When in #7 assmith wrote 'an MK socket and brand new durable uk socket(sic)' I think he may have meant Duraplug plug. These plugs will struggle at 13A because the fuse is inside a nice plastic/rubber blanket. I recommend you swap the steamer's plug for one of these:
13 Amp MK Safety Plug - White | MK (646WHI) - https://www.tlc-direct.co.uk/Products/MK0646.html?source=adwords&ad_position=&ad_id=415703895099&placement=&kw=&network=u&matchtype=&ad_type=&product_id=MK0646&product_partition_id=940253954358&campaign=shopping_excluded&version=finalurl_v3&gclid=EAIaIQobChMIpZyelaf69wIVGojVCh2kqAgAEAQYASABEgKssvD_BwE
For this free advice would you come and strip the wallpaper in our second bedroom?

We have MK sockets into which you can plug the steamer's new MK plug.