Underfloor sfs

[haj]

Gentlemen
On a job doing outside lights and neighbour say can you look at my under floor heating so she says the sfs fuse holder has melted twice! It's brushed steel looks like varilight. So it's spurred from the ring no details for the mat me thinks clamp it see how much it's pulling if its near 13a what do you think about a 20a DP switch instead ? Just concerned it won't be fused down from the ring ! But then it is on an RCD
Cheers

 

[telectrix]

measure the resistance of the element. then ohms law should give you approx. 100watts/sq.m. 13A ( 3kW) would be a bloody huge heater.

 

[haj]

True! But to melt two fuse carriers it must be pulling near 13a or maybe a bad sfs or fuse carrier not pushed fully home. All they can tell me is it was a cable not a mat.

 

[DPG]

Doesn't seem wise to run it straight from the ring, with only the 30A fuse to protect it, RCD or no RCD. Daz

 

[haj]

Agreed clamp it and see what it's pulling.

 

[Beebsdj]

Devimats that I've installed run off a 13A sfs and pull 100W/m if on wooden substrate, 150w/m if on concrete or similar. I'd take the path of least resistance with either a clamp or measure it for resistance. I've been de-rating standard 13A fuses depending on floor sizes and current consumption. TLC sell 7 and 10amp fuses so I fit these if appropriate.

 

[haj]

Well clamped it and its only pulling 7.8amps tops. Varilight brushed steel sfs anybody had any bother with these ?