Viessmann vitodens 200-w. hot water icon dissapeared

[MP plumb]

Hi,

a client of mine has a viessmann vitodens 200-w system boiler. I have come to the job after 2 previous bodge job builders, so im now there to pick up the pieces. I have managed to fix all the problems but one...

The system has a 2 port valve for the hot water in a megaflo, and 3 2-port valves for 3 heating zones.

The hot water icon dissapeared a few days ago, and the hot wouldnt always come on with the programmer set for hot water demand (the cylinder was only luke warm so i know it should of been calling for heat)...so i changed the hot water motorised valve, incase it was being a bit intermittent. The boiler fired up and the motorised valve opens, suggesting everything was working as it should, but still no hot water icon.

The client has said today she is without hot water again but has put the immersions on.

i rung viessmann and one guy said something to do with relays? That is a bit beyond me with my experience, expecially with this boiler as i have never had to work on this make before. He was also saying stuff about the stat.
another guy said he didnt think the hot water icon should even be there.... But obviously is it or it wouldn't of been there all this time until now!!

If you know what the problem is, and if it is to do with the wiring or the stat, can some one explain it to me please?
thanks

 

[MP plumb]

Roger, do you understand the workings of this boiler? If u do, please help!!!Ive been looking into it more tonight and all the manuals I've found suggest it needs an external expansion vessel. is there one inside the boiler? if not, there isn't an external one....certainly not visible. Could you please explain what you mean and if you can guide me any more to the problem?

thanks

 

[payney1974]

The 200W can work with or with out the internal diverter, it is required however if they are running weather comp from the boiler.

Why would you pay so much for the 200 system boiler and then not use the internal diverter valce?

 

[davieplum]

the viessmann 200 system boiler best used with the 4 pipes . i use the viessmann clyinder no need for a 2 port on hot water side as it a hot water proity
use the weather comp brill bit of kit
the 200 comes with expansion up till 50kw then you need pumps and expansion etc,etc
all my top end work i use the 200
if you have underfloor heating use the 200 with a mixing kit