Viessmann 200 boiler, heat but no hot water

[Torsen M]

hi all.

We recently installed a Viessmann B2HB 200 series boiler and a Viessmann vitocell indirect hot water tank. The heating side has been online and working for the last month. We commissioned the hot water tank yesterday, it worked fine for 24 hours. Now, when there is a DHW call on the boiler nothing happens. There is no fault on the boiler and it says the DHW tank temp is 5 degrees C, so it should be firing. The boiler fires perfectly for heating. We have bled and refilled the lines a few times to no avail. We have checked the time programming and every other conceivable setting as well.

Any input or suggestions would be greatly appreciated.

Thanks in advance


T.

 

[Torsen M]

I should add the DHW circulation pump is working fine.

 

[Agile]

So are you in Canada?

 

[Jackrae]

Contact Veissmann Technical, they are usually (sometimes) quite helpful. Could be the servo valve is stuck in the CH mode. I suppose the "obvious" have been gone through, such as time clock actually calling for HW and HW set point actually set higher than current tank temperature, and that you're not on a 5+2 timer with Saturday being a "no HW required" mode.

 

[Torsen M]

Hi.

Thanks for the response. We checked the time settings, they are all correct, good guess though. Unfortunately, Viessmann tech support is closed until Tuesday here in North America.

 

[Torsen M]

Hi Agile,

Yes I am in cold Canada.

 

[Phill Peck]

Are U the installer?

I presume this is a 4 pipe setup?

We're any of the settings/codings changed when it was doing heating only?

if it is installed as a 4 pipe system code 00 will need to be changed from 00:1 to 00:2

 

[Torsen M]

I am a general contractor and it is my project. The installer is on vacation. I had someone else look at it very briefly but he wasn't a Viessmann guy per se and there is nothing "obviously wrong.

 

[Phill Peck]

How many pipes out the bottom of the boiler?

Are there 2 pipes that go solely to the vitocell cyl?

 

[Torsen M]

There are only 2 pipes(1 in/1 out) on the boiler, and then branch to the low loss header and the DHW tank. We followed the Viessmann piping diagram to the letter.

 

[Phill Peck]

Coding needs to be setup to recognise demand from vitocell.
You will need the service instructions under commissioning

 

[Torsen M]

Ok. this may help explain what we did. And the really weird thing is that it worked fine for 24 hrs.

 

[Phill Peck]

It's as above mate these boilers have many setup opinions.
They are not a fit to wall and turn on unit.
The codes tell the boiler what it is connected to how many pumps etc.
If the boiler is left at factory settings it will not fire for hot water.
You need to match the code to your setup.

 

[Torsen M]

We programmed the unit and had it working on the heating side for a month. We also with a call to Viessmann programmed the DHW side and it was working( perfectly for 24 hrs).
That is the crazy thing.