Floorboards up for some light re-wiring.
I was toying with the idea of moving a night storage heater.
1. How do I find out what current the heater is. No markings on
the outside except XT18 series G.
2. The heater is approximately 14 metres from the CU. Can I use
2.5mm T+E to wire it up?
Any help would be appreciated, I keep hitting brick walls...
Agreed, all the specs are based on acceptable volt drop and acceptable
temperature rise in the cable/connectors. If you've ever run 13A through
even a good 13A plug then you'll know that you don't really want to run it
that close to the limits. Notice that 1mm2 was only suitable for cable in
free air, safer with 1.5 or 2.5mm, but I notice Rich has doubts about your
2.5kW rating, was that from a rating plate, there should be one? 2.5mm
sounds safer in case it is 3+kW, it's cheap.
To find the rating plate you have to remove the front/top cover ( ONLY TO BE
DONE WHEN THE HTR IS SWITCHED OFF AT THE MAIN WALL SWITCH, DO NOT TRUST THE
FACT YOU ARE DOING IT DURING THE DAY AND THE E-7 IS OFF IT MIGHT SWITCH BACK
ON )by undoing the 3 screws across the top back of the htr then pull the
panel forward and lift the top panel up a bit the bottom front is hinged on
the front part of the feet it then unhooks off the feet and gives access to
the wiring connections the rating plate is either at the bottom left or the
bottom right down by the feet.
It is standard practice to use 2.5T+E as the supply cable to storage htr's
with a 15Amp fuse protecting the circuit.
A Dimplex XT18 has 3 850Watt elements in it and would be supplied by a
dedicated circuit of 2.5 T+E cable with a Double Pole switch by the heater
and protected at the fuse box by it's own 15Amp fuse ( generally a cartridge
Be very careful if moving it far with the bricks in it as these bashing
around can damage the insulation inside and can then result in scorch marks
on the outer panels as the heat can then escape through the damaged
Thanks everyone for your answers...
A supplemental question... If I have 4 of these suckers wired through my CU
(economy 7). What minimum size fuse should the CU have for them.
Do you mean the fuse for each heater circuit, or feeding the whole off-peak
For the former, 15 or 16 A per heater, as has already been said. If you
mean the latter, then it needs to be at east enough to supply the total load
of 4 times 2.55 kW, i.e. 10.2 kW which equates to 40-odd amps at 230/240 V -
so you'd need at least a 45 A fuse. Normally though this function would be
performed by the supplier's main fuse of 60 or 100 A (depending on the age
of your installation) and the metering equipment would provide a switched
supply to the CU.
Does that help?
PS: storage heaters are rated in terms of kWh of energy storage (per day).
Yours are 18 kWh units - clear from the "18" in the model no. The normal
range of sizes is 6, 12, 18 and 24 kWh. Divide the kWh figure by 7 (hours)
to get the power rating in kW.
Volts times Amps = Watts. So, Amps = Watts divided by Volts. So, to a
perfectly good approximation, on British mains voltage, 240V in practice
and we'll call it 250 just to make for round numbers, 1kw = 1000W draws
4A. Your heaters are 2.5kW each, aren't they? So each one pulls 10A.
3kW ones would pull 12A.
As others have said, it's almost universal practice to run separate
2.5mmsq cables to each heater, each one with a 15A fuse/MCB. In rare
cases - two storage heaters close to each other but far from the CU -
you might run a 4mmsq cable to supply both, fused at 30A.
Sounds fair enough.
This leadds me to my final question... If I run the new storage heater off a
new fuse on the main CU, I can put a timer next to the heater to switch
on/off at off-peak times. Supposing the heater ws accidentally or puposely
left on 24 hours instead of just 7. Would that do it any harm?
Why do you want to run the htr off the normal supply??
if you did and the htr was accidentally switched on for more than 7 hrs I
would think the charge controller i.e. the knob which determines how hot the
htr gets would switch of the elements until it cooled enough for the control
to switch back in if this was an on going situation you may find the cut-out
operating so the htr would go cold.
But at the end of the day it should be on the Off-peak fuse box also main
house fuse should be a 100Amp in the sealed cut out of the boards property.
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