Mira Sport - Failed thermal switches

[Justonemoretry]

I have a mira sport shower and have had to replace two thermal switches in the last 4 months and tonight the third appears to have gone.

The underside of the switch (printed button) appears to have corroded, the second one worse than the original, but I can't see any sign of a leak on the heater tank. Could humidity cause this or is there another reason. I don't want to buy a new heater tank unnecessarily, but feel this may be the only option.

Is there any history if these failures?

 

[Goldberg]

Depending on when you're examining the heater can, any water sitting there could have evaporated, this being accelerated by the heat of the can.

If you run the shower up to temperature, then isolate and whip off the cover, do you see any water then?

Alternatively, as long as you are competent and don't take any risks by poking fingers (or anything else conductive) inside, you can run the unit with the cover removed and see 'in real time' if there's a leak.

TBH I doubt that it's condensation, because there shouldn't be any vapour-laden air within the shower unit, the heat from the can keeping it at bay.

 

[Justonemoretry]

Thanks for your considerations. I feel it is unlikley that it could be condensation as well.

Following ordering the incorrect replacement heater tank in error, i have applied a circle of epoxy around the top of the tank sepaprating the switch from what appears to be some (minor) corrosion of one of the pins coming through it. I will see if that helps, whilst I order the correct tank.

 

[crawfs98]

Hi, similar problem I think, wondered how you got on? My shower is alternating hot and cold unless you turn it right down to 'tepid' - anything higher than that it can't cope and cycles. Low flow light is off. Cleaned the inlet filter and shower head, fine, water pressure is good. Decided to replace the 1563.533 Thermostatic Valve/
Heater Tank 9.8 kW
240 Volt AC - but while removing the old one discovered the 416.41 Thermal Switch is heavily corroded, the lower disk comlpetely corroded away and corrosion on top of the heater tank to match.
Have now ordered a new thermal switch, and hope I can send the new heater tank back unused and clean up the old one - cheaper option . Same thing might happen again though, did your sealant ring do the trick???

 

[Justonemoretry]

Hi first attempt did not work and the replacement thermal switch went through double quick.

I gave up and bought a replacement tank, but in error, bought the wrong one, so had to do another make shift - but this time was more thorough with the ring. In addition I also removed as much of the corrosion as possible from the thermal switch seating. I have an inkling of a memory that remnant oxide causes much more aggressive oxidation, so got rid of it as best able..

No problems so far but I now have a replacement tank waiting for me at the post office as I haven't picked it up yet!!

 

[kevplumb]

might be an idea to apply some thermal grease (heat sink compound) to the stat before fitting

 

[crawfs98]

Thanks very much

Just had a closer look for the origin of the corrosion, mine also seems to be a small leak from the base of one of the pins near the switch recess (the male of the 2 smaller ones) - could be a tiny jet of steam maybe once the element inside gets hot? in which case I might try a bolb of solder over it as the leak will probably breach any normal sealant?