Just changed over to modulating control.
If I ramp up the temp the boiler fires up but I didn't think it would show the 3 lines and state that it's heating when the boiler isn't even on.
I'm just looking for some people's experience on how modulation actually acts between the boiler and the app to see if I'm worrying over nothing.
Thank you.
Best Answer
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From your house description, coupled with the min power on the boiler, I'd say it's almost certainly the boiler modulation. It's behaving exactly as our weather comp does with a similar min power on the boiler. When the flow temp on the boiler drops, the boiler cycles. Nothing else it can do.
The specific behaviour of the tado modulation you're experiencing is likely the algorithms attempting to modulate down and to prevent overshoot - i.e. they'll try to run as low as possible, then modulate back up if it's not working. Weather comp would do the same with indoor feedback, but without it (my system), the flow temp is entirely determined by the sensor outside and goes down only if it warms up outside.
Clearly there are pros and cons to both WC and LC. Unfortunately, neither is perfect.
I probably wouldn't go with WC if I had your boiler though. With a modern house it would cycle even more.
Happy to offer my two penneth. Good luck finding your sweet spot.
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I'm assuming the boiler is on and you have flow when Tado is calling for heat, but the boiler just isn't firing?
When you say you ramp up the temp, is that on the boiler or on Tado?
If the former, it could simply be the boiler modulation ratio, particularly if this is happening in milder weather when the required flow temperature will be lower.
If the latter, I guess that kind of makes sense, because the heat demand v current room temp delta is wider, so Tado then calls for more heat.
Is your boiler itself also fitted with weather compensation? That could also be messing things up. WC and Tado modulation (load compensation) don't play nicely together.
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Yes the boiler is switched on, I'm unsure if there's flow though, how would I tell?
Yeah when I say ramp up the temp, I mean adjust it up on the app.
No weather comp, just tado doing the work.
I just presumed that any difference in temp between the set point and the measured would fire the boiler to bring the room closer to the set point, but then again this is the first I've used a modulating setup so I could just be misinterpreting how it works as wrong since I'm only used to the on-off setup.
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If the pump's running, you'll have flow.
My guess is that it isn't.
I don't think you necessarily have any fault here. All that's happening, is tado isn't actually calling for heat until the room temperature v set point delta is wide enough. That doesn't explain the apparent call for heat on the app though.
How far do you have to ramp it up? A lot, or just a fraction more?
How high is your boiler flow temperature set? Tado could possibly have learned to avoid temperature overshoot.
How did it behave in relay? Did it always fire when the app showed a call for heat?
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As far as I'm aware when it was switched, any time the app showed a call for heat, the boiler was fired up.
On that setup I had my flow set to somewhere between 50 and 60 using the dial on the front of the boiler but I presumed tado would render that dial useless when I moved over to a modulating setup? I haven't moved it but have noticed flow temps in the 30s but as high as 63.
I haven't played around with how far up I need to adjust the temp to get the boiler to fire tbh. Last night, as an example, the room temp was 19 and the set point was 22 and the boiler was off. The app was showing a mix of calling for heat and not calling for heat, but it didn't correlate with actual boiler firing. When i adjusted the app to 25, the boiler did fire up, but again it didn't actually keep going until the set point was met and in the hour or so I had it set to 25, the room never got up to that temp.
I did wonder if tado had some learning to do and wondered if it would take some time to settle in.0 -
If, when Tado calls for heat, your pump is running but the boiler isn't firing, then it's most likely the boiler modulation.
I have weather compensation but my boiler only modulates down to about 7kw, I think. (It's a common problem here in the UK, where most of our boilers are grossly oversized). Consequently, when the heat load is lower than that, the boiler cycles. Exactly the same principle applies with load compensation (Tado modulation). If Tado thinks you need only a low boiler flow temperature to increase a little bit to target room temperature, then the boiler will modulate down as far as it can, but may not fire if it can't go any lower. Otherwise, the flow temperature would be too high.
That would explain why if you ramp up, it fires up. It wouldn't explain why Tado shows full fire though, as I thought it was supposed to show a lower fire when it wanted less heat.
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I did ask the same question on a forum on Facebook and someone said the same as you, that the boiler can't modulate low enough so it could well be that. According to my boiler manual mines goes as low as 7.6kw with a high of 30kw.
The house is a timber frame construction, built in the 90s, 4 bed, so reasonably well insulated with new windows and doors and 300mm loft insulation. Couple that with reasonably low set points of around 18 or 19 per room. It could well be the boiler can't modulated down far enough. I could increase the room temps and see if that smoothes it out any.
The app and boiler discrepancy could just be a glitch. I'll keep an eye on that and monitor the graphs over the coming days and see how it pans out.
Thanks again for your input, it's much appreciated.0