Vaillant ecoTEC pro VUW 246/5-3 - Floor heating not working anymore (hourglass symbol appearing)

[spodoba]

I have a problem with the Vaillant ecoTEC pro VUW 246/5-3 gas boiler. The boiler is paired with an Vaillant eRELAX/vSMART thermostat/application, and I have floor heating. Until recently, everything worked as it should, but now the floor heating no longer works. Hot tap water still works perfectly.
What happens is that whenever I turn on floor heating, boiler starts heating, temperature raises to around 35 °C (I have set max temperature for floor heating at 55 °C), and after temperature reaches around 35 °C, hourglass symbol appears, starts blinking, and boiler stops heating. Boiler is not in summer mode.
I turned off the power for a few minutes from gateway, changed batteries in thermostat, reconnected everything, restarted boiler few times on the button. Issue persists. Hot tap water works, but hourglass symbol appears after a few minutes when I turn on floor heating. If you can help me troubleshoot further, it would be highly appreciated.

 

[CBW]

When it next does it, press the top 2 buttons and should give you a status code, what is it?

 

[spodoba]

Hi CBW,

Thank you for the reply.
After i turn on floor heating, boiler starts working, and if I press top two buttons, i see S.00 what should indicate that everything is ok and heating is working. After minute or two, hourglass appears, and i see S.07. If I wait for a minute longer, S.08 appears. What surprised me is that when i reset boiler again, when it boots up, i can see S.31, what should indicate that summer mode is ON (not sure if that is default after it boots up) . However, there is no umbrella sign, and summer mode is OFF in erelax app.

 

[CBW]

S.31 means there is a demand, but something else is blocking it. S.7 is pump overrun, S.8 is anti cycling, and S.00 is no heat demand.

 

[spodoba]

Thanx for the explanation.
Is there anything else I can do to troubleshoot, or this is a job for an engineer?

 

[CBW]

Not entirely sure, might need an engineer. @ScottishGasMan might have more of a clue than I do.

 

[Johntheo5]

Can you monitor d.40 & d.41, Boiler, flow/return temperatures? you should be able to see these somewhere.

 

[spodoba]

Can you monitor d.40 & d.41, Boiler, flow/return temperatures? you should be able to see these somewhere.

Hi Johntheo5,

Not sure where i can collect this information, but i will try, and provide you results.

Thanks

​

 

[Johntheo5]

Might be something like this?.

 

[spodoba]

Might be something like this?.

View attachment 318955

Thanks you, It seems it might work. I will try tomorrow...

 

[SpecialK]

Do you have a pump on the floor heating manifold? Is it working?

 

[spodoba]

Do you have a pump on the floor heating manifold? Is it working?

No, I don't have separate pump.
Only pump in boiler...

 

[Johntheo5]

How many loops in the UFH, you should/may have flow meters on each loop, can you read them?, is there a motorized (zone) valve on the supply to the manifold?.
You might post a picture of the manifold, also try and monitor those d.40&d.41 readings.

 

[spodoba]

Hi Johntheo5, here is the picture. When you say "flow meters" you mean that label "118m" on the third pipe from the left? It is hard to reach on most of the pipes, but i will try it that is required information. Also, i have checked d.40 and d.41, and they are both °C.

 

[Johntheo5]

Hi Johntheo5, here is the picture. When you say "flow meters" you mean that label "118m" on the third pipe from the left? It is hard to reach on most of the pipes, but i will try it that is required information. Also, i have checked d.40 and d.41, and they are both °C.

View attachment 319141

The flow meters are the individual indicating meters (8) above on the bottom manifold, they read (from top to bottom) 0 to 6 LPM, when you start the boiler these should indicate the flowrate through each of the 8 loops and should read ~ 1.5 to maybe 3.0LPM each.
Likewise with d.40&d.41, when you start the boiler keep watching them and they will start rising up from maybe 25C to 30C, up to a possible 55C,
("What happens is that whenever I turn on floor heating, boiler starts heating, temperature raises to around 35 °C")

THe first thing to look at is those flow meter readings (if any) , as soon as you start the boiler.

Can you also post another picture of the manifold taken more to the left, to see if there is a motorized valve.