Burnt pin on plug

[Gerry24]

Had a call out to look at a burnt 3 pin plug on a convection heater. Just a standard 1363 plug with a 13 A fuse. The line pin was burnt. The customer had removed the cable from the plug so couldn't check to see if a loose connection. Cable seemed fine, no scorching or melted insulation. Checked socket, also fine no loose connections etc. However the heater had been plugged into a digital timer at the time of the fault although the timer still seemed to be working OK. Any ideas what could have caused the fault?

 

[Marvo]

Maybe the plug wasn't all the way home in the timer socket. Maybe the rings in the timer socket don't have sufficient tension. Maybe corrosion on the plug pins. Could be a lot of reasons. I would fit a new plug top and replace the timer as a precaution. If the plug pin burned then the socket it was plugged into will be equally heat damaged even if you can't see it.

 

[Richard Burns]

A lot of digital timers are not rated to take kW of power so the timer may be overloaded. The likely problem is a loose (slightly) connection from the plug to the timer, if the timer is rated at 1kW and has 1.5kW the unit may withstand this but the connections may not.
Replace the plug (to avoid poor connections in future) and check the timer for damage.

too slow, as Marvo said

 

[Knobhead]

One problem with heat damage is you can’t always see it. In a socket the spring tension on the contacts can be weakened by the heat. As a matter of course I’d change both the plug and socket.

 

[Engineer54]

One problem with heat damage is you can’t always see it. In a socket the spring tension on the contacts can be weakened by the heat. As a matter of course I’d change both the plug and socket.

Overheating and burning etc on electrical equipment is generally always, always down to ''Bad Contact(s). That can be from man made terminations/connections as in plug tops and socket outlets and weak or worn internal contacts of electrical accessories. As been stated virtually by all here, all these accessories will now need changing, and that will also include the plug-in timer unit, as that was in direct contact with burnt plug. It could also have been the cause of the plug burning through an internal bad connection...

 

[mogga]

Glasgow transport museum use to have a section about the work of Strathclyde fire Brigade in it was a case with "Electrical faults" mostly adaptors on adaptors and coiloed up flexes I hate these plug in timer things and adaptors as they all seem to pull away at the top under their own weight hence puting the top conection under strain and over time weakening it so much that it starts to burn
While working in a hotel recently the polish receptionist wasnt happy when I removed her phone charger from the socket and told her manager that if I saw it there again Id cut the pins off It was a 2 round pin charger she has forced the shutter open and fitted charger in socket saying she had to "Wiggle it " sometimes to get it to work I asked if she did this at her house she said that all her friends did this with stuff brought from home FIRES waiting to happen

 

[Gerry24]

Thanks all,

I replaced the plug and advised the customer to ditch the timer. He then produced another timer that was cracked, which I also recommended that he got rid off, so he produced a third that was the mechanical dial-up variety that looked OK. I did suggest to him that it may be prudent to replace the socket but he wasn't having that. I agree that these plug in timers are a potential problem and as for socket adaptors, whenever I see them, which I do a lot, I always recommend that if they must use an adaptor that they buy a surge protected socket bar. But I'm sure that most people just ignore the advice once I'm gone.

 

[nickblake]

this could also have been caused by a loose fuse holder , had one just the same recently where the pin had melted this was caused by the socket connection being bent so that when the plug was inserted it didnt make proper contact did you check the socket for a possible fault

 

[ruston]

Thanks all,

I replaced the plug and advised the customer to ditch the timer. He then produced another timer that was cracked, which I also recommended that he got rid off, so he produced a third that was the mechanical dial-up variety that looked OK. I did suggest to him that it may be prudent to replace the socket but he wasn't having that. I agree that these plug in timers are a potential problem and as for socket adaptors, whenever I see them, which I do a lot, I always recommend that if they must use an adaptor that they buy a surge protected socket bar. But I'm sure that most people just ignore the advice once I'm gone.[/QUOTE


Replacing the socket in such circumstances is a recommendation in the code of practice for inspection and testing for in service equipment. (pat testing), if this may apply in this case.

 

[Gerry24]

this could also have been caused by a loose fuse holder , had one just the same recently where the pin had melted this was caused by the socket connection being bent so that when the plug was inserted it didnt make proper contact did you check the socket for a possible fault

Thanks for your comment. I did check the socket. Didn't find any scorching, loose connections or apparent heat damage. Also, shutters working OK. I did recommend to the customer that it would be prudent to change it as a precaution, especially as i was on site anyway, but he didn't want to spend the extra few quid.

 

[Rampage]

We get a lot of burnt sockets / plugs. The record for a new BS 1363 Socket becoming unusable is 48 hours!
Usually the switch stops working and there are burn marks around the Line hole. Other times the insulation around the Line pin on the plug melts, or the fuse gets hot and the plug cover melts.
Using BS1363A Plugs helps!

 

[Piratepete]

Hi
I've just been dealing with exactly the same problem but with 3 convector heaters in the same room on 3 different sockets! In all cases the live pin on each plug has overheated as has the live on the sockets. IMHO it is the fuseholders in the plugs that have the poor connection, so that the pin overheats damaging both the plug and socket over time (10 years in this case).
I've fitted new sockets and more importantly good quality MK plugs - should last another 10 years!
Cheers
Pete

 

[nickblake]

an awful lot of heaters are 3kw does make you wonder about the suitability of plugs and sockets for 3kw i have to admit i do prefer doule pole switches for this , and really 3kw and above should be installed on their own circuits

 

[Piratepete]

an awful lot of heaters are 3kw does make you wonder about the suitability of plugs and sockets for 3kw i have to admit i do prefer doule pole switches for this , and really 3kw and above should be installed on their own circuits

Yup. I agree. But they arrive with a 13 Amp plug fitted and a choice of feet or wall brackets.
I did suggest putting in switched fused spurs - his comment was 'Na, I'll replace them again in another 10 years!' I can't argue with that!
Pete

 

[needasparks]

I think its a very common thing to happen with this set up as the weight of the timer and plug on the pins makes it pull away from the socket, put a large load through a pin with poor conection and only one thing will happen.
I Went to a job the same a couple of years ago, the customer had bought three heaters and time clocks as it was cheaper than getting a heater with built in timer. This socket was behind a curtain and completly melted down the wall, could not think of a more dangerous situation but it happens everywhere and he was just lucky i guess.