I have a Vaillant boiler which seems to have developed a problem today, the central heating side is working fine but I can no longer get hot water, it just comes out stone cold. I'd be very grateful for any thoughts on why this problem is occurring. I think the boiler is getting the message to heat water as it kicks in when I open the taps, just doesn't seem to warm the water
Divertor valve?
The various models that are out and about have very different details in there operations. VCWs and Sines have complex servo operated diverter valves. Turbomaxs have directly operated diverters. Turbomax+s have a PCB operated diverter.
I think this fault is less likely to be on a Turbomax than with other models.
Thanks for your input Ed, I dug out the manuals today, the model is either a turbomax plus 824E or 828E (fitted before I bought the property). As an update, from messing around today it seems that this problem is intermittent, with the boiler failing to heat the water for the majority of the time. Sometimes the water was heated to lukewarm and when water of a high temperature was obtained the temperature seemed to fluctuate from very hot to luke warm. Does this shed any more light on the matter? Thanks very much for any advice you can offer.
Just to confirm this is a boiler with an LCD digital temperature display?
Q1: Does the boiler start the pump& fan in responce to a reasonable flow at a HW tap a) Sometimes OR b) Always?
If a) then there is a problem with the water flow sensor or (PCB maybe). Or in extreme cases with the water supply.
Q2: Does moving the DHW termperature control (the top one) alter the behaviour?
Q3: Does the yellow LED flame on/off indicator cycle on/off/on/... during HW mode?
Q4: What flow rate are you getting at the taps?
If all is well you should get a consistant flow rate around 8-14 litre/min with a comensurate temperature rise. Poor pressure/flow on the supply and/or secondary heat exchanger scaling can make for problems.
HTH
I've been hearing stories that the electrically operated diverter valve on this model is a problem. Not that Vaillant will admit it though. I tried phoning their technical department about it, when ours started playing up and they disclaim any knowledge of a problem.
Resetting the boiler, which excercises the valve, usually results in it working for a while. I still haven't changed ours yet, I suppose I should really...
Lee
I have not had (or heard of) any problems with this component on the dozen or so I've fitted. Maybe I've been lucky.
The poweroff rest position for the diverter valve is with the CH flow blocked so effectively it's in DHW mode.
Even when the valve is fully in CH position there is still some residual flow of heat going to the DHW exchanger (this is how the internal bypass is implemented).
The diverter valve gets excercised after reset.
A sure way to tell if a systematic problem has occurred with a component is when the spare part is a 'upgrade kit'.
In article , Lee Blaver writes
Mmmm, my 2 year old turbomax plus has done this a couple of times, no dhw until I switch it off for a short while :-(
Why are Ferrolis so unpopular? The diverter valve seems to be the achilles heel of most combis
Fans and pumps still account for a lot though. Perhaps one possible problem with the Ferrolis is that the replacement cost of the secondary heat exchanger is high.
I still haven't been able to get Vaillant to confirm it, but apparently there was a batch of valves with a manufacturing defect produced in
2000. The faulty valve has a sticker saying "A43". Allegedly.Lee
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