Dead shower

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Problem: Mira Sport 10.8Kw shower suddenly packed up.

Symptoms: No lights (not even "standby"), no action. Nothing. 240V showing as far as thermal cutout above heater tank.

Block circuit diagram http://www.mirashowers.com/onlinecatalog/pdf/p3279_2a.pdf doesn't show enough detail to work out exactly what's going on inside. I suspect the cutout, but would that cause everything including standby lamp to die?

Is this the likely cause? Thanks.
 
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Hi Paul,

Just had a look at the MI you linked to. Looking at the fault finding chart at the back suggests that if no lights are lit on the shower the fault is in the power supply to the shower, or at least a loose connection at the shower terminal block. I presume you've checked the MCB/fuse, the isolating switch, RCD device, etc.

If the thermal cut-out were operating, at least the standby light would be on, unless I've misread the chart - did it very quickly. Should I also presume that you know how to safely check for voltage at various points in the circuit? If not, I can give you a few pointers. Have you checked for voltage on the neutral connections? A break in the neutral would have the same effect as a break in the live supply.
 
Thanks for that Chris. Yes, there is power to the unit as far as the thermal cutout and you needn't worry about my ability to test a circuit!

The problem with their simple diagram on P9 is that it doesn't show enough to give any meaning to voltage checks. I was working on the assumption that an overheat condition would isolate the whole system - but if it did, the overheat neon wouldn't work of course. I wonder if a different kind of failure in the thermal sensor could cut the supply at its neck. Otherwise, it looks like a dreaded PCB failure.
 
Surely it's a simple matter to check for voltage on the outlet of the overheat cutout or to do a continuity test across it? What does this reveal?
 
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That's the next step. Trouble is, that wretched diagram doesn't tally with what's actually there. Will let you know how it pans out.
 
Bang goes that theory. The thermal cutout is fully closed and is delivering enough juice to the PCB to light a 100W lamp (making sure it could cope with a load and wasn't just dirty contacts somewhere).

What's left? A bloke in Plumb Center said one of his customers had a similar problem which turned out to be a faulty Stop button. Unlikely to be that as it's a simple push-to-make and wouldn't disable the whole unit if malfunctioning. Unless... unless...

Nope, not that either. Just tested for a short in case it doesn't like being powered up with this closed. But it's OK.

Not much left but the PCB. Any other ideas?
 
Have you checked for voltage in the neutral wires (like I suggested before)?
 
Neutral is at 0V to earth. Live to neutral reads 240V (actually 215V but my multimeter is old and shows the same at any other point on the ring main). Circuit after the thermal cutout can power a 100W bulb happily yet the shower must only take a few mA when dormant.

What am I missing?

New PCB is £77.50 from Mira spares. Bleedin ripoff - probably costs less than a fiver to make.
 
You can buy a new Mira Sport 10.8 kW for £177 (plumbworld). That way you don't risk wasting money on a PCB that might not actually be faulty.

Plus you could try any part from the new one as a substitute for any suspect part in the old one to determine the fault precisely (providing the showers identical, or at least compatible). You would then have the option of ordering the correct spare for the old one, and end up with two good showers - solving a Christmas present problem too.

Alternatively the old shower can at least be a source of free spares for the new one (thinking ahead a bit there).
 
Good thinking, Pike. As a last shot I have emailed the Shower Doctor (showerdoc.co.uk) who claims to be a whizz at diagnosing faults and sending the right part. If he thinks it's the PBC then we will have to make a decision... like where to put that extra shower :LOL:
 
Chris - to close the chapter (hopefully), Shower Doc was certain it's the PCB from the symptoms. "They go all the time on that model" said the gruff scotsman.

I've ordered a replacement. The unit isn't that old and it still leaves us over £100 in pocket. If he's wrong he's a dead scotsman.

Paul
 

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