blowing cartridge fuse



Hi guy's this is my first time in using a forum so please exuse any mistakes,


I went to a customers house today as her econermy 7 storege heater fuse keeps blowing if she leaves her water switch on over night,
Though she has a seperate fuse box for the storage heaters and the water heater, I cant seem to find what is causing it to keep blowing,

She doesn't have a timer it is direct into a switch,
The elements are only 6 weeks old and was ok when i put a test on it,



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The fuse can pop if it is overloaded or if there is a fault. What size fuse and what size element? What are the IR readings for the circuit?
hi thanks for the reply,

it is a 15amp fuse, and a 3kw element,

what is IR ?

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ops sorry, i didn't do a resistance test, i just did a coninuity test on the element to see if it was ok,
A continuity test won't reveal much as the conductors will be at the wrong temperature. All you will see is a circuit or no circuit. How many amps does it draw when in use?
unforgonatly im not sure as it is the one that comes on, on the off peak,
why does it blow the fuse for the storage heater rather then blowing the fuse for the water heater it self?
Exactly which fuse is blowing? What size? The service fuse or a 15A storage heater circuit fuse?
If she leaves her night economy 7 water heater switched on over night, (off peak element)
In the morning she will have a blown fuse (cartridge 15amp) on one of the storage heaters,
If she doesn't turn the night water heater on and only use the boost element the fuse for the storage will be ok,
Has the immersion heater and a storage heater somehow been connected into the same fuse/circuit?
That was my only thoughts, i took the covers off both box's but there where to many cables to chase, and the cables are coming from the back of the box's so couldn't really tell, ?

I have took out the fuse for the storage heater and switched on the off peak water heater just to see if she gets a full tank of hot water with out any problems,

Wont know until tomo though
If this is just recently happening. It sounds like one of the storage heaters may have developed an element fault. It could be short circuiting and blowing the fuse.

It could also be a fault in immersion heater element or in the cables leading into the heater itself. They can become quite brittle over the years and are also subject to mechancial damage in the airing cupboard.

Bare in mind the storage heaters are not very likely to be connected to an RCD, so any element or insulation faults will cause a short to earth and will only be picked up by a blown fuse.

I'd be worth while getting someone into check them over.
Sounds more like an overload fault to me, immersion heater pulls approx 12.5A, doesn't leave much capacity in the circuit to connect a storage heater.
Hi thanks for all reply's,

After taking out the fuse for the storage heater for one night, the neon on the night element didnt come on nor did the storage heater work duing the off peak time,

so im more sure now that someone has connected up the night water heater to the storage heater and when it becomes the right time in the night, they both click in and blow the fuse,

After seeing what work has been done in the house i wouldnt be too surprised,

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