In which case the problem is within the storage heater or plug and btw, it’s best not to use plugs with such heaters
Are you saying BS1363 plugs are not fit for purpose?
I would agree the modified BS 1363 plug is not suitable for long use at the maximum of 13 amp, but it seems the heater talked about here is only 1000 watt, not 3000 watt, so a BS 1363 plug should be ample. The BS 1363 plug was designed with solid pins able to assist in dissipating the heat produced by the fuse, the modified design with insulators on the live pins has reduced the energy which can be dissipated, so with items using high power over a prolonged time yes I can see how it is better to use a fused connection unit which is larger so better able to dissipate the heat, but 500 watt is hardly what I would call high power.
However from
the instructions
WARNING - The electrical installation of this heater must be carried out by a suitably qualified or trained electrician, and be in strict accordance with current wiring regulations.
The peak supply must be connected via a switched fused spur with a fuse rated suitably or the appliances flex, the off-peak supply, via a 20A double pole isolated switch.
In both instances a plug and socket arrangement MUST NOT be utilised. The contact separation to be a minimum of 3mm.
Failure to follow these instructions will mean that the manufacturer’s instructions have not been adhered to. THERE ARE NO EXCEPTIONS.
It continues to say "• Not suitable for connection via a plug top" I would always use a whole plug not just the top, it does make one wonder who wrote the instructions? It is clearly old as refers to IEE regulations, been IET now for around 15 years.
The instructions are for 5 models with 5 different power ratings Input rating +5% / -10% 936/1020W 1435/1560W 2042/2220W 2540/2760W 3024/3300W so with the higher ratings I can see why it says do not use plug and socket.
It seems the heater can have single or duel supply, there is a lot of control within the heater
and to try to write how to test would be silly, when there is already an instruction set. Including how to connect it to a smart phone.
So is Dimplex saying the BS 1363 is not fit for purpose? It does seem they are, however if it did not have a plug and socket then the tests done to date could not have been done. I will admit I am not sure where off peak heating is going, seems we are loosing the radio 4 time signal, so maybe we now need smart control of storage heaters? I am sure there will be many more posts after mine, and I look forward to seeing the comments.
I realised the plug socket in the wall had warped a bit by the live prong,
Clearly this needs addressing, if Dimplex had not stated that plug and socket must not be used, I would say replace both, as when a socket has an over heated plug in it, the spring tension can be lost which grips the pins in the socket, so both need renewing, but the statement by Dimplex seems to point to not using a plug and socket arrangement.
In the main sockets in a home are arranged as a ring final, the idea is a single 32 amp overload can supply many sockets for use with temporary loads. However with high loads found with storage heaters the radial system is better suited, and homes designed for the Economy 7 supply normally had a dedicated fuse box for that supply, over the years fuse boxes have been replaced with consumer units, and the system has changed as to be frank, the old storage radiators did not store very well, heat leaked out when not required, so they needed a boost, the Economy 10 was aimed at curing the problem.
But things have moved on with heat pumps and the like. With a 60 amp supply and a three story house, I am never going to heat electric, main reason is lack of heating during a power cut, so I can't really advise on how to cure the problem, but it does seem likely you will need an electrician to visit, as said interesting to see what others say.
