Unvented Cylinder - suddenly no hot water

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Tk_rtmt

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Hi,

I have a bit of a mystery - I've searched for answers but can't seem to find any reports of the same issue so hope someone here can help...

We have lived in a 2-bed, purpose-built, all-electric flat for 5 years now (property is ~20 yrs old).  It has an E7 supply, storage heaters (that we never use) and an Oso Direct Unvented Cylinder for hot water.  The cylinder is controlled by an adjacent Horstmann Electronic 7 controller that we have always had set to heat the water overnight for 3 hours.  It also has a 1 hour boost button that my husband has used for evening showers recently.

Last Sunday, our morning showers seemed cool and by Monday, were cold.  It was then I checked on the cylinder and found the display on the controller so faint it was barely readable.  I tried the boost - no light.  I tried changing the time to the middle of the off-peak heating times and no light for the timed heating either. I thought the controller might be gone so bought a new one, which came today. I've just installed it (new front into original back) and still nothing works. Furthermore, looks like the original was fine, just whoever installed it didn't flick the switch on the back that keeps the display running on battery first. (Pretty sure the cylinder is plumbed in incorrectly too but that's another issue)

So... is it possible that there is no power passing to the controller and thus onto the cylinder?  I have read that usually it is the cylinder's immersion heaters or thermostats that go haywire but would both go at once?

There's a 13A fuse between the CU and the Horstmann that I have replaced (did that first).  The MCB in the CU is switching on and off without complaint - I assume that means the fuse inside there is fine?  I do think it's electrician time but am down with flu and, frankly, could do with a shower and some flat- tidying before getting one in, so was wondering if there was anything else I could try myself in the meantime?

Many thanks in advance for any pointers!

Sorry, when I say "both go at once", I mean both the overnight heater/stat and the day boost heater/stat. 

 
Haha. As expected.  Thanks for the reply anyway! Sparky coming tomorrow.  :B

 
2No. Immersions...

Anyway, just to provide a conclusion, a loose connection had caused a wire to melt in the box housing the 13A fuse.  Box and wiring to it replaced.  All back in working order. 

 
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