UK Diyer : FCU warming up over approx 6- 8 months before switch starts arcing out

[Jim mac]

FCU warming up over approx 6- 8 months before switch starts arcing out, supply in kitchen is from weirdly up stairs to fcu, then down to double unwatched socket for dw and washer, then up to switched double socket above worktop, never have both on at same time, and a desk top pc again now and then plugged into top socket , fcu is 13 amp, has it been wired incorrectly, any way round this slight over heating? Many thanks in advance

 

[littlespark]

ok... so fcu has 13A fuse in it, presumably.... and regs say you can have as many socket outlets on a FUSED spur as you like, with a load not exceeding the 13A....

A washing machine and diswasher will both be circa. 10A each... so if you only have one on at a time... it should be good. However, if both are on together, or anything else plugged into the socket above... you could be stretching the 13A beyond its limit for some considorable time. (it will not instantly blow at exactly 13A.... it could take 14, 15, 16A for an extended period before finally giving up.... and heating up as it does)

Another possibility is a loose connection behind the FCU... a very high load passing through a loose screw can cause arcing, heating, and eventually damage caused by the heat... which could result in a fire.


It is highly recommended that large appliances be on their own radial circuit nowadays. (over 2kW load), but if impractical, then having them each directly plugged into a single wall socket is preferred. Absolutely not through an extension lead.

 

[Jim mac]

ok... so fcu has 13A fuse in it, presumably.... and regs say you can have as many socket outlets on a FUSED spur as you like, with a load not exceeding the 13A....

A washing machine and diswasher will both be circa. 10A each... so if you only have one on at a time... it should be good. However, if both are on together, or anything else plugged into the socket above... you could be stretching the 13A beyond its limit for some considorable time. (it will not instantly blow at exactly 13A.... it could take 14, 15, 16A for an extended period before finally giving up.... and heating up as it does)

Another possibility is a loose connection behind the FCU... a very high load passing through a loose screw can cause arcing, heating, and eventually damage caused by the heat... which could result in a fire.


It is highly recommended that large appliances be on their own radial circuit nowadays. (over 2kW load), but if impractical, then having them each directly plugged into a single wall socket is preferred. Absolutely not through an extension lead.

Thankyou for the reply so, if I wire 2 single sockets in series with the load coming from the fcu would that suffice?

 

[littlespark]

You can do that, but it’s not recommended for high power appliances.

For high power appliances, it can be 1 spur to 1 socket for 1 appliance.
Or just have 1 accessible socket, so it ensures only 1 appliance can be used at a time.

Still would check for heat damage behind the fcu. It can be tight with 2 cables in, (presumably) and 1 out.
Also presuming the cable size is correct for the load.

 

[Jim mac]

You can do that, but it’s not recommended for high power appliances.

For high power appliances, it can be 1 spur to 1 socket for 1 appliance.
Or just have 1 accessible socket, so it ensures only 1 appliance can be used at a time.

Still would check for heat damage behind the fcu. It can be tight with 2 cables in, (presumably) and 1 out.
Also presuming the cable size is correct for the load.

Think you have hit it on the nail sir, as the supply wiring comes down from upstairs it's just a single cable ie 2.5mm twin and earth, would that then be a no no connecting a spur then 2 single sockets plus the double above worktop?

 

[Dan]

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[Jock from the north]

ok... so fcu has 13A fuse in it, presumably.... and regs say you can have as many socket outlets on a FUSED spur as you like, with a load not exceeding the 13A....

A washing machine and diswasher will both be circa. 10A each... so if you only have one on at a time... it should be good. However, if both are on together, or anything else plugged into the socket above... you could be stretching the 13A beyond its limit for some considorable time. (it will not instantly blow at exactly 13A.... it could take 14, 15, 16A for an extended period before finally giving up.... and heating up as it does)

Another possibility is a loose connection behind the FCU... a very high load passing through a loose screw can cause arcing, heating, and eventually damage caused by the heat... which could result in a fire.


It is highly recommended that large appliances be on their own radial circuit nowadays. (over 2kW load), but if impractical, then having them each directly plugged into a single wall socket is preferred. Absolutely not through an extension lead.

hi ,have you ever carried out a practical experiment on a 13 amp 1362 buss man fuse .managed to get 20 amps flowing thru before plug top was to hot to touch ,that was for 30 mins .all done in a safe environment in work shop with relevant ppe .allowed the fuse to cool down then managed to get 30 amps flowing thru for approx 2 mins before disconnection [with flash] really wonder what the point of them are to be honest .a relic to the old days.questionable 1.00/1.25 flex from amazod with steel conductors [cheaper than copper ] would surely start to melt by that time

 

[littlespark]

A fuse indeed can carry more than its rating for some time, as I’ve mentioned… but like your experiment, it’ll heat up.

Mostly, it gives end users a rough idea of what should and shouldn’t be done.

If it says 13A, then dont, in practice, plug in things that exceed that 13A .