Hot water problem with Heatslave 15/19

[rxangus]

Hi,

According to the manual, the burner should come on under hot water demand. Mine doesn't unless the shower temperature control is cranked up to maximum which then is too hot to use. Any suggestions what might be wrong would be appreciated. At the moment I get a short warm shower until the heatslave tank is empty then the shower goes cold, sometimes for minutes. Eventually the burner comes on and the water runs hot again - presumably because the refilled heatslave tank demands it?

I'm on a private water supply at around 1.2 bar if that is significant?

Thanks for any help

Angus

 

[slapper]

Sounds as tho the motorised valve is the problem,you need someone to check it out

 

[rxangus]

Thanks for the reply. I've booked a Bosch engineer visit for next month so will see what they say. I presume you are referring to the diverter valve which might well be the problem as I have had the radiators heat up a couple of times (but not always) when this problem happens.

If it is the valve, why would the fault be overcome by turning the shower temperature to max?

Thanks

Angus

 

[picasso]

I cant find the instructions for your combi but I would hazard a guess at the dhw diaphragm. (if it has one)

 

[rxangus]

Thanks,

Is the diaphragm within the diverter valve? If so then why would the burner come on just because the shower temperature is turned to max?

I see there is a flow switch mounted on the valve. I would have thought that the burner would come on any time the flow switch detects DHW demand but its operation seems to depend on there being sufficient hot water in the hot/cold mix. It's the same issue with the kitchen mixer tap.

Sorry for the questions as I know the Bosch engineer will probably be able to answer them but I am an electrical engineer with an inquisitive mind!

Thanks

Angus

 

[slapper]

Demand for hot water triggers paddle in flow switch,brings boiler on,diverter already in DHW position,makes no difference on shower cos as soon as theres hot water being drawn off boiler should strike up.

You could have a sticky flow switch also,turn cold water to boiler off,take top of flow switch off by unscrewing, clean and replace. Sometimes debris gets in there and prevents paddle moving to trigger boiler sequence.

 

[picasso]

I found a copy of the instructions, there is no diaphragm, it detects hot water demand by the flow switch, there is a flow limiter and filter in the flow switch body, the filter might be blocked and slowing the flow enough to not trigger the flow switch or the switch is just worn, probably why you have to put the shower on max to get enough flow.

 

[rxangus]

Thanks for your help guys - much appreciated.

Angus

 

[rxangus]

Just an update in case it helps anyone in the future:

Turns out the UV water filter on my private supply had clogged over time and reduced the flow to the point where there was insufficient flow to trigger the flowswitch under DHW demand so the boiler wasn't kicking in. Replaced filter and all is now well.

Angus