Vaillant ThermoCompact - Hot water /CH priority issue

[outofmytree123]

Hi

I have a Vaillant ThermoCompact(model is either 615E, 620E, 624E, 628E) . I think its about 4 years old. The pressure in the system is set to around 1.5bars.

I have 2 issues with this little blighter:

1. The CH works fine just by itself and the hot water works(more or less see problem 2) by itself. However when the heating kicks in the water goes freezing cold. I understand the system cant do both simaltaneously but would like the preference to be the other way around. i.e HW takes priority over CH. Is there a setting for this or just a fault?

2. The HW is a bit tempremental. The shower can get very hot but will often drop in temperature to luke warm before going to warm again. It seems to be worse the higher the pressure you put the shower on at. The problem can occur at any time, not just when we have the washing machine on or something. The mains water pressure is quite good.


Anybody able to help on either of those?

 

[weareleeds]

With pre heat turned off & system cold turn on a hot tap if c/htg pipe under boiler starts getting hot you probably have an early diverter valve which will need swapping

 

[outofmytree123]

Thanks a lot for that, will try it later tonight. 2 important things to mention.

1. I made a mistake on the model and it is a Vaillant Turbomax Plus.

2. I forgot to mention that when I switch off the "warm start" which I'm guessing is preheat we get No HW at all.

 

[pannierstan]

2. I forgot to mention that when I switch off the "warm start" which I'm guessing is preheat we get No HW at all.

Oh dear

 

[outofmytree123]

weareleeds - yes the central heating pipe does get warmer with preheat off and like i mentioned the HW is stone cold when preheat is off.

pannierstan - was the "Oh dear" comment just a general vote of sympathy or do you know if point 2 means something very bad?

 

[outofmytree123]

Has anybody any ideas what the problem is?

 

[cross thread]

diverter valve ,domestic diaphgram

 

[outofmytree123]

gordongas - "diverter valve ,domestic diaphgram".....is this 2 seperate faults or 2 possibilities for the failures?

 

[weareleeds]

It doesn't have a diaphragm as i posted days ago you have an early diverter valve which needs changing (part about £100)

 

[whistler]

Just had the same problem with Turbomax 824. Replaced the diverter valve - cost £77 and took about half an hour to do. I now have hot water again.

Seems its a common problem with the rubber ball valve sticking.

 

[outofmytree123]

whistler - did you change it yourself and where di u buy the valve from?

Thanks

 

[whistler]

I dont know if we are supposed to name companies on the forum, but if you do a google search on Vaillant diverter valve you will find lots of places that supply them. They seem to average around £90 but shop around and you will find one at £65 plus vat.

I replaced it myself its very easy if you are handy with a spanner!

Drop the front panel by loosening the two securing screws. You will see a brass valve on the left hand side with a black motor unit on its right hand side.

 

[outofmytree123]

Thanks for everybody's help, especially whistler.

 

[outofmytree123]

whistler - did you need to depressurise or drain the heating system? or are there valves which stop any water?

 

[ChrisR]

did you need to depressurise

You'll get frightfully damp if you don't...
Manual is on the Vaillant site