Unusual Viessmann 111w problem

[jakubjakub]

Hi,
I have a problem with Viessmann 111w
I have a Vicare sensor and app.
It goes like this :
If I have a boiler in DHW only everything works as it should, but then I switch it to DHW and heating. Temperature in a room is 21 degrees. I set the boiler to come on when the temperature is 17 degrees.
Every time I run a hot water, boiler comes on, fills a hot water tank, and as soon as it switches off, it dumps a lot of hot water into the radiators. Every time.
I put my baby to bed at 7pm (and my heating is on from 7) and I still have a shower, do washing up, wash my hands etc. Every time it dumps hot water to the radiors. By 10-11pm when I go to bed , temperature in the bedroom is 25-26degrees!

I had Viessmann engineer coming 4 times, he can't figure out what's wrong. Now they start telling me it's normal, that it has to dump that water to radiators. Surely that's not normal. My bedroom gets hotter every time even I don't want it to. And it doesn't dump any hot water when only in DHW mode.
Anyone might know what's going on? I'm not wrong it's not normal, am I?

Anyone's got the same boiler and could check for me what does your boiler do?
I would really appreciate any help.
Thanks
Jakub

 

[ShaunCorbs]

It is common for the end of heating the store for it to dump heat into the rads but tbh it shouldn’t be that much maybe a warm rad closest the boiler

 

[jakubjakub]

Why would it need to do it if it doesn't need to do it when in DHW only mode?
I have downstairs radiators off only two in the bedrooms running as I use wood stove downstairs.
Anyway, even if I had all rads open, every time I run hot water , more and more hot water gets dumped into the rads, and if it's not very cold outside , temperature inside will rise and rise. Is that normal?
I'd expect my thermostat to make sure temp is constant, so I can put heating on and rads to get warm only when temp drops, not that I have to switch heating off when using hot water.. hope I'm making sense..?

 

[ShaunCorbs]

Because of pump overrun eg to cool the boiler down afterwards

 

[jakubjakub]

Because of pump overrun eg to cool the boiler down afterwards

It doesn't need to cool down when in DHW only mode . Why is that? I'm confused, sorry

 

[ShaunCorbs]

It should do it all the time strange

 

[Gasmk1]

It doesn't need to cool down when in DHW only mode . Why is that? I'm confused, sorry

In hot water mode it is only heating the water and topping up what you have used

 

[jakubjakub]

In hot water mode it is only heating the water and topping up what you have used

But in heating and hot water mode it's only heating up water too, as the thermostat is set for the heating to come on only when the temperature drops below 17(or now I set it to 3degrees), so the heating doesn't come on at all

 

[king of pipes]

A 111 is a big output boiler even when it modulates to its lowest output it will heat 2 rads in minutes , then where does the heat go ? That heat needs to go somewhere typically a auto bypass is fitted to allow the boiler to displace to heat in the boiler once it has reached it set temperature either by the Vicare app with weather compensation or the internal themostat if one is fitted ? put up some pictures of your boiler and pipework please . Kop

 

[jakubjakub]

A 111 is a big output boiler even when it modulates to its lowest output it will heat 2 rads in minutes , then where does the heat go ? That heat needs to go somewhere typically a auto bypass is fitted to allow the boiler to displace to heat in the boiler once it has reached it set temperature either by the Vicare app with weather compensation or the internal themostat if one is fitted ? put up some pictures of your boiler and pipework please . Kop

It's a wireless thermostat. But heating doesn't come on. Only hot water is being heated and a water tank inside a boiler filled .
Everyone keep saying the heat needs to go somewhere, but it doesn't happen when heating is completely off (DHW only) . Nobody seem to be able to explain why does a heat needs to go somewhere when Ch on, but not when off, when the boiler does exactly the same thing in both - just heats a water for the cylinder.

 

[king of pipes]

If heat is creeping into the heating when the hot water storage is being replenished ? then it could quite possible a faulty 3 way valve internally inside the boiler , these boilers have a commissioning procedure in which you match the pump speed and system output to the heat curve required this is usually done when the boiler is installed do you have a external weather sensor fitted ? again a few pictures would help us ?? . Kop

 

[jakubjakub]

If heat is creeping into the heating when the hot water storage is being replenished ? then it could quite possible a faulty 3 way valve internally inside the boiler , these boilers have a commissioning procedure in which you match the pump speed and system output to the heat curve required this is usually done when the boiler is installed do you have a external weather sensor fitted ? again a few pictures would help us ?? . Kop

The heat isn't creeping into the rads. As soon as the hot water storage has been replenished and a burner goes off, the three way valve opens for a few minutes and hot water rushes to the rads . (It doesn't do that when in DHW only mode). Happens every time the hot water storage has been replenished with hot water (so every time I use hot water , really)
They replaced 3 way valve, main board and bypas (or so I was told) and nothing changed.
Now they try to say it's probably normal, but untill someone can explain to me why it happens in Ch mode and not when in DHW only mode I won't accept it. That's why I'd love to find someone who has the same boiler so I can check if it behaves the same way.

 

[Basher]

The heat isn't creeping into the rads. As soon as the hot water storage has been replenished and a burner goes off, the three way valve opens for a few minutes and hot water rushes to the rads . (It doesn't do that when in DHW only mode). Happens every time the hot water storage has been replenished with hot water (so every time I use hot water , really)

I don't know if you've looked at the Installation and Service Manual, but page 71 (click on thumbnail below) seems to describe the Viessmann logic of heating the stored water. It mentions when the heating circuit pump and tank circuit pump are supposed to run.

https://viessmanndirect.co.uk/files//420164c1-b300-46d6-8e79-a9d1010f3519/Vitodens%20111W%20B1LB%20Installation%20and%20Service%20Manual.pdf

Having read it a couple of times it's still not clear to me (!), but it doesn't sound far off what your boiler is doing.

If only you could find the right person to talk to in Viesmann, they might be able to tell you if what you observe is what is expected to happen - or (preferably) not!
Sorry I can't offer any insight - just thought you might be interested in the attached if you haven't already seen it.
PS. The 'few minutes' you mention is supposed to be 30 seconds - maybe something up with the delay period?

 

[Gasmk1]

Because when heating off it inky heats up to the desired temp of the tank there will be no excess heat

 

[jakubjakub]

Because when heating off it inky heats up to the desired temp of the tank there will be no excess heat

Why would there be excess heat with a heating set to on , when it never comes on as the desired temperature set on a thermostat is 3 degrees?

 

[jakubjakub]

I don't know if you've looked at the Installation and Service Manual, but page 71 (click on thumbnail below) seems to describe the Viessmann logic of heating the stored water. It mentions when the heating circuit pump and tank circuit pump are supposed to run.

https://viessmanndirect.co.uk/files//420164c1-b300-46d6-8e79-a9d1010f3519/Vitodens%20111W%20B1LB%20Installation%20and%20Service%20Manual.pdf

Having read it a couple of times it's still not clear to me (!), but it doesn't sound far off what your boiler is doing.

If only you could find the right person to talk to in Viesmann, they might be able to tell you if what you observe is what is expected to happen - or (preferably) not!
Sorry I can't offer any insight - just thought you might be interested in the attached if you haven't already seen it.
PS. The 'few minutes' you mention is supposed to be 30 seconds - maybe something up with the delay period?
View attachment 82178

Thank you for that. Just read that a couple of times (not very clear to me either !) and it says the cylinder loading pump stays on for 30 sec, and 3 way valve on. Wouldn't that be the valve ON for a cylinder loading circuit?

 

[jerrysmith]

It is possible that a faulty 3-way valve is causing heat to enter the heating system during hot water replenishment. This valve is responsible for redirecting hot water to either the heating system or the hot water cylinder, and a malfunction can hinder proper water diversion, leading to heat infiltration in the heating system. The suggested commissioning procedure serves as an effective method to assess the functionality of the 3-way valve.

During commissioning, the pump speed and system output are adjusted to match the required heat curve, optimizing boiler operation and heat distribution. Installing an external weather sensor can further enhance boiler efficiency by allowing it to adjust heat output based on outside temperature, preventing overheating and energy waste. If issues persist, it is advisable to contact a qualified engineer to inspect the boiler, diagnose the problem, and propose a suitable solution.