Mira Electric shower not heating up

[JoeJoe]

Have had one of these

(10.8Kw)

for the last 10+ years, used daily.

3 years ago or so the water temperature started to play up (would turn cold suddenly when in use), and at the advice received here I cleaned the filter on the water inlet, which fixed it, and no problems since.

Yesterday it started to misbehave again: under Medium or Low setting the water is completely cold. When set to High it almost reaches acceptable temperature when the dial is on max, but not hot enough. Anything below that is pretty much cold. Usual setting for this time of year is around 1, perhaps 2 o'clock.

I tried to clean the (very dirty) filter again, but it had no effect.

Any idea what to try next please?

[Andy Burns]

Does that model have a dual element? if so, sounds like half of it may have failed ...

[Chris Hogg]

How many elements in the heater tank does it have? Having three settings suggests three. It sounds as if at least one, and possibly two, have failed in some way, either gone O/C or the switches have failed.

[JoeJoe]

But even when it is set to High the water is only lukewarm when the dial is set to max... So two elements are completely dead and one "half dead"?

[JoeJoe]

Also, just noticed that Mira offer a repair service. They are not clear about pricing (£80 call out charge + parts?). A new equivalent shower is £220, and as long as the plumbing/wiring haven't changed (very likely) I am happy to replace it myself.

Is it worth fixing considering its age, or has it reached the end of its working life and other parts are likely to fail "soon", i.e. a new one would be a better solution?

[John Rumm]

It might have two elements - switched in parallel, with one being more powerful than the other. So it can switch low power element, high power element, or both to give the three settings.

If you have a multimeter, its easy enough to test. Isolate the power, and take the cover off. Look for the wires connecting to the small boiler can. I am guessing there will be probably be 4 - a neutral, an earth, and two switched lives.

If unsure, post a photo where we can see it.

If you measure the resistance across the element between neutral and the first switched live, then the second. You may well find your problem there. If not it could be the switching has (partially) failed. The one you picture looks like it might have electronic switching - that can make it harder to test when powered down, but you might be able to swap the switched lives to the boiler and then reassemble and test to see if the fault behaviour changes.

[Brian Gaff]

No but the flow through will not be enough with one heater to be hot enough, it incrementally heated I think. Brian

[Brian Gaff]

Depends on how disruptive the messing about with a no doubt differently plumbed unit might be. On your comments about heating. When the filter is clogged the flow is reduced and only one element will probably be on anyhow, or the whole thing would overheat and die. With the greater flow you need more heat and that is proven by your experience.

Brian

[Chris Hogg]

[Andy Burns]

some use 1=low, 2=med, 1+2=high

[John Rumm]

Ah, that's handy... In fact they have a nice picture of the boiler:

Looks like two switched lives with microswitches. Probably the bits I would test first unless there was something else looking obviously knackered.

[JoeJoe]

Found the booklet/installation manual (sad, I know).

Is this diagram of any help in working out what may need replacing?

[JoeJoe]

mine, I believe, is the J95D - the newer model (this one is the J92)

[tony sayer]

Yes chuck the electric one and fit a power shower off your hot water tank:)

Did this yeas ago not and its fine hot proper showers.

Mira event thermostatic IIRC we used..

around 350 quid but worth it!.

[JoeJoe]

No tank - a combi. 3 showers, one (v good) off the combi. Other two electric.

[John Rumm]

If the combi is fairly powerful (>= 35kW) then it will run two good showers at once. A smaller 24kW boiler will do a couple of reasonable[1] ones at once.

[1] Where "reasonable" is probably double the flow rate you get from an electric shower - but not quite up to the standard you get from a combi with a single shower.

[John Rumm]

That looks pretty similar to the online one listed earlier. The three likely candidates are the heater itself (1563.505) or the stat (416.41) or the switching unit (1563.510).

Only way to find out is to test them - starting with the heater.