Stealing lights power for towel rail

[akist]

I have forgotten to allow a dedicated circuit for a towel rail on all bathrooms and as a solution i have hijacked power from the lights circuit. The wiring is 1.5mm to the lights switch. The wiring to the towel rail is also 1.5mm. The towel rails on the market are 250W mostly, some are a bit more. The electrician frowned and said the lights fuse is 8A as the 1.5mm wire can carry max 16A, but we derate it, and that I would need an additional 5A fused switch just for towel rail. Extra work and damage to the walls.

Why cant i just use the lights circuit as is? The towel rail would pull 1 maybe 2 amps, the LED lights maybe 0.1A, and the fan maybe 0.5A, so we have plenty to spare.

 

[EFLImpudence]

I have forgotten to allow a dedicated circuit for a towel rail on all bathrooms

I wonder if anyone has a dedicated circuit for a towel rail.

and as a solution i have hijacked power from the lights circuit.

Ok.

The wiring is 1.5mm to the lights switch. The wiring to the towel rail is also 1.5mm.

Ok, so you have the latest fashion of oversized lighting circuit wiring.
You might not have a neutral at the switches.

The towel rails on the market are 250W mostly, some are a bit more. The electrician frowned and said the lights fuse is 8A

Usually 6A.

as the 1.5mm wire can carry max 16A,

Actually 20A.

but we derate it,

No we don't. It is hugely overrated.

and that I would need an additional 5A fused switch just for towel rail. Extra work and damage to the walls.

No you don't, but a switch would be handy.

Why cant i just use the lights circuit as is?

You can.

The towel rail would pull 1 maybe 2 amps, the LED lights maybe 0.1A, and the fan maybe 0.5A, so we have plenty to spare.

There you go. Get a new "electrician" who knows what he is doing.


Most people would run a cable from the nearest socket as it is usually closer and then you likely do need a fused switch.

 

[ericmark]

A normal ceiling rose is rated 5 or 6 amp, so although the regs allow up to 16 amps for lights, in the main we are limited to 6 amp.

230 watt is one amp, so you still have 5 amp to spare, and today with LED lamps, likely only using an amp per floor, so it would have enough power to do it, and with 1.5 mm unlikely to exceed the 3% volt drop.

So unlikely to cause a problem, I would fit a FCU with 1 or 2 amp fuse, and would look first at the ring final, but it could be done.

 

[JohnW2]

A normal ceiling rose is rated 5 or 6 amp, ...

The 'rating' of a ceiling rose is not really relevant to what one might choose to feed from the cable supplying the rose, since any such additional current would not go through the rose.

230 watt is one amp, so you still have 5 amp to spare, and today with LED lamps, likely only using an amp per floor,

... or far less. I doubt that many people have 230W worth of LEDs per floor.

so it would have enough power to do it, and with 1.5 mm unlikely to exceed the 3% volt drop.

I won't even bother to comment on that

So unlikely to cause a problem, I would fit a FCU with 1 or 2 amp fuse, and would look first at the ring final, but it could be done.

As EFLI has said, it would usually be more convenient to take a feed from a sockets circuit, in which case an FCU would probably be necessary. However, there would really be no point/need for sn DCU if the towel rail were fed from a lighting circuit.

Kind Regards, John

 

[DetlefSchmitz]

there would really be no point/need for sn DCU if the towel rail were fed from a lighting circuit.

I can't imagine fitting an electric radiator without a way of switching it off though.

 

[JohnW2]

I can't imagine fitting an electric radiator without a way of switching it off though.

That is true, and, as we know, FCUs (sorry about the typo - the keys are adjacent on the keyboard ) are cheaper than DP switches, so you have a point.

Kind Regards, John

 

[Taylortwocities]

Whichever circuit you decide to use, please make sure it is protected by a 30mA RCD

 

[securespark]

The 'rating' of a ceiling rose is not really relevant to what one might choose to feed from the cable supplying the rose, since any such additional current would not go through the rose.

Not quite sure what you are saying here, but I wouldn't want to use a 6A rose as a junction box on a circuit exceeding 6A, assuming it did.

Just like you wouldn't want to use a 32A junction box on a 50A shower circuit.

Surely that is exactly what the additional current would do - go through the loop terminals of the rose?

 

[EFLImpudence]

... but 13A sockets are used on 32A circuits.

 

[JohnW2]

Not quite sure what you are saying here, but I wouldn't want to use a 6A rose as a junction box on a circuit exceeding 6A, assuming it did.

Maybe you wouldn't

Just like you wouldn't want to use a 32A junction box on a 50A shower circuit.

I hope you mean "one" (or "I"), rather than "you"- since, again, maybe you wouldn't

The 'rating of terminals in JBs and other accessories are, at least in my opinion, a bit of a joke - all that really matters is whether the conductors will fit. If a screw terminal is tightened properly, the conductor is in intimate contact with the metal body of the terminal - which invariably has a greater CSA than the conductor being connected to it, so I personally have no real interest in anything other than whether or not the conductor will fit.

Kind Regards, John

 

[akist]

Outside each bathroom there is a 1.5mm live supply into a light switch and from there a 1.5mm cable to the lights. The live supply goes straight to the fusebox and has its own fuse. I add another cable from the light switch to the towel rail and another cable to the fan. I also add one more gang for the towel rail, while the fan cable is joined with the lights, so the fan comes on when the lights are on, while the towel rail has its own switch (or gang). That means the towel rail is controlled from the location of the light switch so it is convenient to use. I have also added another backbox next to the light switch, in case I want to do something clever with the towel rail, eg "stay on for one hour" type of thing, but I have not researched this.

 

[Taylortwocities]

Do you mean FUSE? Most old style “fuseboxes” do not provide RCD-protection.

 

[akist]

By "fuse" I mean whatever circuit breaker they use.