Wiring towel radiator heating element

[Robotman]

Hi All,

I've just bought a 300w heating element for my towel radiator. In terms of wiring, was thinking of taking a spur using a 1.5m2 cable from my double socket to an FCU, the flex of the heating element to the FCU.

Does that sound right and what amp should the FCU be?

Thanks in advance for your advice.

 

[martygturner]

300w = 1.25 amps so a 3 amp fuse should be ample but what does the manual say as its got the inrush rating on it, ie the difference in resistance of a cold v hot element...Cheap ones can ask for a fair few amps to warm up, my 300w chepo soldering iron draws 5 amps for a second or so on warm up, but my expensive 800w draws 2 amps as its got a pre warmer and thermostat.

 

[Deleted member 267285]

Going on ohms law, the amp rating will be approx 1 amp, so likely 3 amp fuse, I think the switches are rated at 13 Amps

 

[Robotman]

300w = 1.25 amps so a 3 amp fuse should be ample but what does the manual say as its got the inrush rating on it, ie the difference in resistance of a cold v hot element...Cheap ones can ask for a fair few amps to warm up, my 300w chepo soldering iron draws 5 amps for a second or so on warm up, but my expensive 800w draws 2 amps as its got a pre warmer and thermostat.

Thanks for your reply.

Just checked the online manual it has the following, i'll check the device when i get home:

Voltage: 220-240VAC
Power:100W-1000W

 

[Harry Bloomfield]

was thinking of taking a spur using a 1.5m2 cable from my double socket to an FCU

That would need to be 2.5mm.

 

[Robotman]

That would need to be 2.5mm.

Great, thanks for that.

 

[Robotman]

Going on ohms law, the amp rating will be approx 1 amp, so likely 3 amp fuse, I think the switches are rated at 13 Amps

Thanks, i cant find a 3 amp switched fused spur. Would i have to make to with a 13amp switched fused spur?

 

[ETAF]

you just change the fuse in the spur
switches are rated higher than 13A

Just pull out the fuse holder - remove the 13A and replace with a 3 or 5A

 

[Robotman]

you just change the fuse in the spur
switches are rated higher than 13A

Just pull out the fuse holder - remove the 13A and replace with a 3 or 5A

oh I see, thanks.

 

[Harry Bloomfield]

Thanks, i cant find a 3 amp switched fused spur. Would i have to make to with a 13amp switched fused spur?

That's because they do not make them, take the 13amp fuse out and replace it with a 1, 3 or 5amp one. The fuse is only to protect the cable.

 

[EFLImpudence]

That's because they do not make them, take the 13amp fuse out and replace it with a 1, 3 or 5amp one.

That must be confusing to the OP. 1A will not be suitable for the radiator.

The fuse is only to protect the cable.

So, 13A will do then.

 

[RandomGrinch]

Going on ohms law, the amp rating will be approx 1 amp, so likely 3 amp fuse, I think the switches are rated at 13 Amps

Just for info
Ohm's law still applies, but (as @martygturner says) the resistance of a cold resistive heating element can be a lot lower than it would be at its working temperature.
This can lead to a brief inrush current of several times the normal working current, until the element is hot.
In this case, a 3A fuse should be fine.
If there were nuisance fuse blows, move up to a 5A fuse.
Or as EFL says, a 13A fuse would also be OK!

 

[Robotman]

@EFLImpudence and @RandomGrinch, thanks for your inputs.

 

[winston1]

So, 13A will do then.

Indeed.

 

[winston1]

That would need to be 2.5mm.

No it wouldn’t. 1.5mm is perfectly adequate for a load that cannot exceed 13 amps.