Heater on 1.5mm lighting circuit ?

What's the other loading on the circuit?

A 500 watt space heater is just going to try and heat the whole loft; you'd probably be better to wrap trace heating tape round the tank and pipes and then insulate over that.

Owain

But I've removed the loft above the bathroom: now the tank's at the top of a very tall room and over it is an OSB3 ceiling, 8 inches of kingspan , osb3 and an EDPM rubber roof.

How about a flat "terrarium" heater (get from a pet shop or Amazon) under the tank with a froststat. Only a few 10's of Watts and quid.

Electrically fine, but 500w is pretty excessive. You'll boil it. The plastic tank will then collapse, dumping boiling water over someone asleep underneath.

NT

Then it's in the warmest part of the room and as long as you heat your bathroom it's not going to freeze.

Owain

I don't heat that bathroom, except for the frost heater which I had on in December and may have kicked in once or twice.

It's on a lot of extension leads.

I'm hoping to put it (and a fan) a new lighting circuit.

Or a 40 watt bulb in a biscuit tin. :-)

bulb failure -> freeze -> leak. No. Those days are past.

NT

Oh right.

In that case a 500 watt heater should keep the room reasonably warm.

Shouldn't really be on a lighting circuit but we did worse things in past times.

Owain

I've never heard anyone poo-poo in principle a 500W floodlight on a "lighting circuit" so why deprecate a 500W heater? I wonder if it might help to rebadge it as a "500W lamp for those sensitive to infrared radiation" :)

ISTM you were right in your first reply ("What's the other loading on the circuit?"). If that's OK I'd say the main thing is to label clearly the circuit in the CU and in the paperwork so there's no confusion as to which circuit powers the heater.

These days with low power lighting most lighting circuits can more than cope.

There was a time with incandescent lighting when I recall guidelines of how many rooms should be powered by a single circuit.

I also recall a 6A breaker tripping from having a 500W floodlight running with other incandescent lighting.

You probably don't need anything like 500W. Look at greenhouse heaters at less than 100W and plug it into a frost-stat.

If the tank is sitting on the joists in the loft remove the loft insulation from under the tank. Still insulate the sides and top of the tank. You can get insulating jackets for tanks but I've found a roll of insulation pre-wrapped in silver foil also works and is easy to remove for maintenance

Put 2-off 100W bulbs in series and they'll last forever.

The frost heater turns itself on when the temperature is less than 3 or 5 degrees and thus is off for over 11 months a year (and much cheaper than having 100watt bulbs on 24/7)

I guess it should be on a fused switch, hopefully on the same circuit as the bathroom light, fan, and a few other lights.

Or a 60 watt bulb inside the room, under the tank. remove insulation from under the tank and extend it up, around and over the tank so the heat migrates up from below.

Of fill the loft with legionaires bacteria and condensation.

Oh - that's a reason for having the tank in the loft, so it keeps cool? I've been worrying about it freezing. But on very hot sunny days the loft can be super hot..

Remember the quartz bathroom heaters? The round ones that actually replaced the bathroom light.