Melted 13amp Spur switch

[luke teague]

Feed a storage heater on economy 7. The 13amp spur switch for it is to the side of it wasn't working properly and the phase input looked a bit melted.

I have tested all the wiring IR is fine and so is continuity and Zs thats without the melted broken switch as it fell apart in my hands.

It felt loose as if the mechanism had come apart inside, so I took it apart to see. It hadn't come apart, but melted and feel apart. there was a hair line crack all the way up the switch.

The most melted part is the neutral supply connector, the cable covering had even melted slightly an inch or so up the cable.To me this is quite alarming, it doesn't look that far away from starting a fire.

The circuit is on a 16 amp mcb and not all that old. but even the 13amp fuse spur never blew.

I will change the switch and reposition it as its very near the heater and the heat can not help things.

I'm worried that the same thing is going to happen again, has anyone seen anything like this before, or know what could be causing it?

The storage heat tested out of and i was thinking if it was that surely the cable for the heater would be damaged instead.

 

[sivoodoo]

loose conection proberbly.

 

[luke teague]

the connections where all tight. could it be the switch its self.

 

[WarrenG]

Loose connection sounds like the obvious reason, but if the connections were tight then something else isn't right.

Sometimes you can have a loose connection and because of the heat build up at the connection point, the connection appears to be tight and therefore misleading.

I would check polarity throughout the circuit (including the heater) because it seems strange that the fuse/MCB did not go with this problem?

Re-test everything again, fit a new (decent quality) switch and check the loading for the circuit.

Warren

 

[chrissyh]

The fact you state that the neutral was the most melted part would suggest either a loose neutral connection at the termination or a weakness in the manafacured internal FCU connections.

 

[andy pandy]

check connections at origin of circuit aswell.

 

[Spudnik]

Cheap product i reckon.

Coupled with the fact that it most likely would have been a loose connection and the terminals seized or melted with heat build up.

I have also seen badly terminated conductors where the screw has been put through the insulation instead of gripping the bare copper. This can also contribute to high resistance in the terminal.

Just replace it with a better quality product, and whilst your at it, have a check of any other heaters that are connected to similar makes of spur.

 

[bonjovi]

just a thought all the storage heaters ive done have NEVER been on a 13 ampspur always a 20amp double poleswitch what is the load of the heater
1 amp 250 w so 1000w or 1kw is 4amp so 3kw is 12 amp =4x3 or thier abouts for easy working out if you exceed the rating that is why you nearly had a fire

 

[BillR3]

As per Bon Jovi

It should have been a 20A DP switch to supply this heater that is why it has over loaded and burnt out.
What size of wattage is the heater?

 

[luke teague]

As per Bon Jovi

It should have been a 20A DP switch to supply this heater that is why it has over loaded and burnt out.
What size of wattage is the heater?

but surly a DP 13amp spur is safer and if it draws more than 13amps the fuse should blow.

 

[Spudnik]

but surly a DP 13amp spur is safer and if it draws more than 13amps the fuse should blow.

Exactly.

However, fuses do tend to rate lower than they can handle.

Some could sit for days letting 14-15 amps through.

 

[sivoodoo]

The rating of a fuse is the current carrying capacity of the fuse, not the current that will make it blow, as jason states.

 

[bonjovi]

have you ever seen a flash inside a immersion heater switch when it is first switched on manually this is because when the contacts on the switch close together when it is operated just befor the gap closes a spark jumps acoss causing a flash this is why the contacts on that spur are of a certain thickness and size to be able to withstand that damage which is being done over along period of time (its lifetime ) but if you increase the load the spark is greater causing greater damage which the contacts are not designed for this is why you have to upgrade your switch to a heavier switch such as 20 amp dp switch with thicker contacts s as not to cause damage either the switch stops working or it burns out which noboby wants as regards the fuse should blow im not sure it would if its a fault it would blow but sometimes a fuse wil carry alot more load than it was designed for imm sure someone will tell us after reading this hope ths helped

 

[///ajd]

Something similar has just happened to me.

See picture:

The fuse didn't blow, but the jumper lead between the fuse and switch has melted. I think its a cheap switch that can barely cope with 13amps - but surely the fuse, even though it might carry a bit more than 13amp, should blow BEFORE the switch starts to melt!

The jumper lead was preinstalled in the switch and appeared to be fitted professionally at manufacture - I confess I assumed it was and didn't check whether it has been installed correctly (i.e. insulation properly stripped) so this could be a possible cause i.e. poor connection.

This is a screwfix varilight FCU switch BTW.

 

[nickblake]

I totally agree with bonjovi storage heaters as well as immersion heaters should always be on a 20 amp DP switch not a fused spur , running these items on fused spur's causes the contacts on the fuse carrier to run hot even on relativly low loads 2kw say and these are on for 7 hours econonmy 7 .then cool down heat up cool down heat up ,the connection the get weak and dont make a tight contact then eventually end up melting so if you come across this on a periodic i feel it should be a Code 1 ,i say this as the exact same thing happend on an immersion heater which had been wired into a fused spur set fire the the house luckily they faimily had smoke detectors and got out ,as the regs state protection against fire .