Western Star Condens communication error

It sounds like there may be an inbalance between your room thermostat and thermostatic radiator valves (or smart valves if you have them).

Are your radiators getting hot?

What type of valves are on your radatiors? What are they set at?

If you have thermostatic radiator valves they could be cutting the flow to the radiators at a lower temperature than your room temperature setting, eg. if they were all set to frost guard then they wouldn't open and so the heating water would just be circulating around the pipes and the one radiator that shouldn't have a TRV.

What is your heating water flow temperature set at?

If the water circulating in the pipes and radiators is at that temperature already then, no matter what the room thermostat says, the boiler will not fire until the circulating water temprature drops below the set flow temperature.

That means that if you only have water circulating in the pipes and one radiator it will heat back up quickly then take a few minutes to cool again, and repeat.

If you have TVRs make sure that they have not all been turned down low.

P.S. Condensing boilers are at their most efficient with a heating flow temperature of around 55 C.

However boiler engineers do tend to set the flow at 70-80 C becase that will heat a room more quickly, - but they are not paying your gas bill so aren't bothered about efficency.

The valves are fully open—there are 10 radiators in total. It seems this happens when Tado requests the minimum heating output: the temperature drops from the set 22°C to 21.9°C, triggering the heating, at which point this behavior begins. However, if I increase the set temperature to 22.5°C, it modulates perfectly and runs smoothly.

Apologies, I hadn't noticed that you had a Tado controlling things.

I'm not familiar with how they work but I'm sure that someone who does know more will be along soon.

(It still sounds as if you are hitting some kind of boundry imbalance at 22 C).

Hey ​@Atesz0209 

I’m glad to see Nukecad has already stopped by here with some helpful advice and questions. 

Nukecad mentioned a possible boundary that may be in place stopping it at that 22°C, are there any limits in place if you have the Tado app?

I tried searching Google for a manual for the boiler but seemed to come up short other than one that appears to be behind a pay wall.☹️ I wonder if there’s anything that may help in the manual if you have one to hand?

It’s very hard to tell if it’s likely to be an issue with the Tado or the boiler itself. It might be worth reaching out to both manufacturers to see if they have any advice on it. I’ve linked above for Tado’s contact details, for the boiler, it looks like the Westen Star is part of the Baxi group for which you can find contact details for here.

So, the problem is this: the thermostat in the Tado app is set to 22°C. When the temperature drops to 21.9°C, Tado signals to the boiler that there is a demand for heat. On the Westen boiler, the radiator icon starts flashing, the pump kicks in, the flame ignites, and it begins heating—but only for about 30 seconds before the boiler cuts the flame. Meanwhile, the circulation continues, and the heat demand remains active; three minutes later, it starts up again and repeats the exact same cycle. However, if I increase the target temperature in the app to 22.5°C, it ignites and modulates properly, without constantly switching on and off. I suspect that when the temperature only needs to rise from 21.9°C to 22°C, Tado requests such a low flow temperature that the boiler—by its very nature—exceeds that target, causing it to shut off the flame.

What you describe sounds exactly what I suspected in my first reply, it sounds like the radiator valves are closed at 22 and so the water is just circulating around the pipes (and it's hot enough so when it does cool it only tskes 30 sec to heat again) - however if the Tado is set to 22.5 then the valves open and the water can circulate through the radiators. A larger volume of water that takes longer to heat.

So the question is are the radiator valves smart Tado ones?

Not sure if this will be of help to you, but it looks worth a read:

https://heatable.co.uk/boiler-advice/tado-smart-heating-thermostat-review

Just to ask - How was the system being controlled before you got the Tado?

Not smart valves; just standard heads, all fully open.