The storage heater in the lounge keeps blowing the 15A fuse in the consumer unit. When replaced it will last about a week and then will blow again. The thermal fuse inside the heater remains intact. It is a Creda 3.4Kw TSR Slimline model and is approx 15 years old. Does anybody have any ideas as to what could be the cause?
14.2 Amp (240/3.4*1000) is close to 15 amp are these cartridge fuses or re-wireable? It could be a slight volt rise at night or a real fault on heater. Really not a DIY job to check out, needs expensive meters and working live to do some of the tests. The Thermal fuse has very little to do with current drawn the heaters run at about 900degC in center of unit and if this over shoots or insulation breaks down the thermal fuse is to help prevent fire. Sorry to be so negative but both electrocution and fire in the home are possible if you make mistakes so better to get someone who knows what they are doing.
what fuseboard is it, you may be able to get someone qualified to temporary change fuse for a 16 amp mcb if old wylex board to see if it still trips.
Is it a cartridge fuse or
If its rewirable does the old wire look burnt and broke (overloaded) or is it blown up into tiny copper balls (fault).
If rewirable I take it you are using proper 15 amp rated fuse wire
Do you know someone that can safely check exact voltage.
3400 divided by voltage =current
Therefore LOWER the voltage the higher the current
If your supply is as low as 226volts which is possible it would exceed 15 amps.
A second thought electric elements don't use the same power hot and cold are you are close to limit. May be original fuse was motor rated this would allow the heater to draw more current while it heats up. The rated wattage is at the rated voltage so if rated at 230 volt instead of 240 volt that's 14.8 amp i.e. 15.56 ohms if then it really has 240 volt thats 15.42 Amps. I know is seems it should work other way but its rated Watts not real watts. I do remember working abroad and a 25 amp fuse went and I worked out it should have a 32 amp fuse but they would not fit as carriers were next size up so temp to keep it going I took inside out of 32 and put it in 25 but I was worried and could not understand how it had been working in first place when normal electrician for that site came back I asked him and it seemed he had done the same when he first fitted it. In Algeria we had problems getting parts and of course it is possible someone has done that with you and cheated in some way which is why I would get it checked as there may be nothing wrong with heater. But the risk of fire is too great to take a chance you really do need it checking properly. We are all watching space to see what type of fuse was fitted.
My first 3.4 kW creda storage heater was fed from a switched & fused wired outlet. The electrician had no difficulty sourcing a 20 Amp fuse to fit. It would have taken the standard range of 3, 5, 13 Amp fuses commonly found in these outlets and in our 3-pin mains plugs.
The fuse-box was wired for high-load under-floor heating, and it was this feed that he used. (ps - the switch was back-lit by a neon).
BS1363 range of fuses should only be available to a maximum of 13 amp these are 1 inch long. The 1.25 inch fuses used in cars etc do go up to 50 amp but should be too long to fit in fused spur. The whole idea of the BS1363 range of fuses is that you can't get over a 13 amp fuse to fit. I think some cheated drilled end of fuse and put in 20 amp fuse wire in or something like that?
Hi and thanks for all of your replies. Some further information to add is that storage heater are connected via a non-fused connection unit at the wall and is protected by a 15amp cartridge fuse in a Wylex consumer unit that is about 8 years old. The storage heater was taken from an old installation, refurbished and fitted in my lounge in 2000, hence the wiring 8 years old and the heater 15 years old.
For the record and so as not to cause 'student confusion'
the rated load of 3.4 kW will be at a rated voltage, say 240v.
As the resistance of the element is fixed, lower volts will result in lower amps, not higher as suggested.
Conversely at night when heater first comes on (late evening peak TV time) volts may well be 'cranked up to meet demand' and higher volts = higher amps. Ohms law!
I have 1st-hand experience of PYRO type elements, on my Tricity Contessa Delux cooker, giving a short-to-earth, only when V.hot, tripping the house RCD.
The elements in storage radiators are made of the same PYRO, with the same life-time.
I would strip-down the radiator and renew ALL the elements, given its age. P.S. -- the front panel of these radiators has a fragile inner lining, which will likely crumble at this age. New panel is due, and will be no problem to order, but might take some time for your electrical supplies factor to obtain.
The front row of sintered iron-oxide bricks in the radiator need to be removed to get to the space that the elements are housed in. Even when new, these bricks show cracks.
It may be worth thinking of dumping the radiator, and fitting a new one, as they are not expensive.