Vaillant Ecomax. Intermittent HW - aqua sensor problem?

[Burrower]

Hi,

Our Ecomax failed to give any HW today. After looking around the net, mainly this forum, it appears the HW flow is not detected.

I have checked the diagnostic mode - d.22 - it is 0 (no flow). Also the 'tap' icon on the LCD display was failing to come on.

I cleaned the 'turbine' as suggested on another thread. No luck. Checked again and noticed the shaft was a bit bent. Maybe this was causing the turbine to bind. Straightened it and replaced - and the HW worked again - great. d.22 checked, now 1. 'Tap' icon showing. Cool.

Later on, it stopped working again. Went through same routine. Cleaned turbine housing. Turbine washed and certainly looks like it should turn, and turns freely when examined. Replaced, no joy, so repeated a few times and eventually it worked (again). This hasn't lasted - it now works, but only intermittently.

So I have the following options:
1) Aqua sensor 'Turbine' bent (possibly binding on the housing) albeit now not obvious to the eye. Buy new one.
2) Halls sensor (I think this is the right name) that detects the rotation of the turbine is broken. This seems (to me) unlikely - surely it would either work or not work as it has no moving parts itself.
3) Something else...

Grateful for any suggestions.

-- Tim.

PS. Not sure if this is relevant, but the condensate pipe has got blocked with ice a few times over the last few days. Its a bit damp therefore but mainly around the bottom of the boiler. The connection to the halls sensor may have got wet at some point, but the plastic box which appears to contain the electronics has remained dry.

 

[The831Bunny]

If the white plastic of the turbine has cracked or flaked then replace the aqua-sensor complete. It comes with a new cherry switch/sensor. After about 6-10 years the plastic turbine deteriorates and stops spinning correctly.

Check the cherry switch connection has not got damp and gone green inside the terminals in the connector.

I have also seen PCBs fail on recognizing the aqua-sensor. Its usually a total failure, not intermittent.

I'd insulate your condense pipework too. It should be 35/42mm if run externally, not unlagged overflow.

 

[Burrower]

Ta for the info.

The boiler is (we think) 8 years old, but the plastic body of the turbine looked fine to the eye.

I'll check the connection tomorrow. It has indeed got damp in there due to leaks caused by the condensate pipe icing up.

About 6" of the overflow pipe is outside, though it has a 2' stone wall to get through which won't be much warmer than the snow outside. I realised earlier today from trawling this forum that its the wrong pipe. The same happened last winter - we called the gas man who told us what the problem was but omitted to tell us about the pipe size. We'd hoped then that it was the upshot of the particularly harsh winter (we only moved here last October) as we couldn't really believe that the previous owner would have had it happen for seven winters without sorting it. On the other hand, given the state of the house in general that was perhaps a naive assumption.

The sensor is actually working OK at the moment - I did wonder if I'd opened the mains stop cock enough when I put the water back on, so opened it by another turn. No visible difference to flow but it seems to work now. I'm rather hoping this is it, as opposed to just being coincidence, even if it makes me feel a bit of a dunce for not opening it up properly in the first place, as access to the bottom of the boiler is poor - I don't fancy having to change the sensor until we get round to doing the kitchen (this house has a long 'todo' list - as the kitchen is 'functional', its a low priority).

-- Tim.