Baxi Ifos wheather compensation kit

[jacoscar]

Hello, I have a Baxi combi boiler managed by a Tado thermostat (on/off), plus additional thermostats in each room controlling radiator valves. I normally run the boiler flow at 60 deg and I was looking for ways to add opentherm, when I bumped into something else, this wheather compensation kit

Baxi Multi-Fit Combi IFOS Kit - Screwfix

Order online at Screwfix.com. Provides a cost-effective, easy to install way for installers to comply with building regulations. Simply clips into the flue and connects to the boiler PCB. Suitable for use with horizontal and vertical flue systems up to 4m in length and is compatible with all...

www.screwfix.com

The Tado system knows the outside temperature by using some online services and should compensate its demand for heat based on that; however, all it can do is turning the boiler on and off, so if it needs 50% it will (roughly speaking) just turn on the boiler for 20 minutes and off for another 20 minutes (kind of pulse width modulation); it does this to modulate the heat request: this depends on how much heat the house is losing and by how quickly I'm demanding for heat (for example if I've set a much higher than ambient target temperature or if it's just maintaining the current temperature). No matter what, flow temperature will always be 60deg.

How does the weather compensation kit actually work? It seems like the user selects a climatic curve and it will adjust flow temperature based on external temperature (?). Is it measuring external temperature or, as the sensor is installed on the flue terminal, the fumes temperature? I would imagine if it's supposed to measure the external temperature, then it wouldn't need to be installed clipped to the flue, unless this is to minimise holes in a wall

 

[gas112]

What baxi combi do you have ?

 

[jacoscar]

What baxi combi do you have ?

Baxi Duo-Tec Combi 28 HE A

 

[gas112]

https://mediacdn.baxi.co.uk/-/media/websites/baxiuk/files/product-literature/ifos/ifos-combi-installation-and-commissioning.pdf?v=1&d=20200928T174109Z

yep its suitable and reasonably easy to fit into a duotec but they are designed to work attached to the flue so would not work correctly fitted directly on a wall .
you would need this one .

Baxi Outdoor Wall-Mounted Sensor - Screwfix

Order online at Screwfix.com. Outdoor wall-mounted weather sensor that works with all Baxi combination boilers to give fuel savings and improved comfort levels in the home. Raises energy efficiency performance of the boiler. Meets the requirements of Boiler Plus when installing a combi boiler...

www.screwfix.com

 

[jacoscar]

https://mediacdn.baxi.co.uk/-/media/websites/baxiuk/files/product-literature/ifos/ifos-combi-installation-and-commissioning.pdf?v=1&d=20200928T174109Z

yep its suitable and reasonably easy to fit into a duotec but they are designed to work attached to the flue so would not work correctly fitted directly on a wall .
you would need this one .

Baxi Outdoor Wall-Mounted Sensor - Screwfix

Order online at Screwfix.com. Outdoor wall-mounted weather sensor that works with all Baxi combination boilers to give fuel savings and improved comfort levels in the home. Raises energy efficiency performance of the boiler. Meets the requirements of Boiler Plus when installing a combi boiler...

www.screwfix.com

Sorry, I didn’t mean I wanted it attached to the wall, I was asking if it needs to sense the flue temperature or the external ambient temperature: it sounds like the latter.

 

[jacoscar]

So I’ve installed the Baxi ifos sensor on the bottom of the flue.
I’ve been working out the curve that I need; the display only shows number from 10 to 30 while the manual shows curves from 5 to 35

In the last few days, I realised that if I want to maintain my current schedule with heating going off at night I need the highest curve I can set (30), otherwise it takes too long to heat my living room (only 3° rise in 12 hours).

I’m trying to see if I can use a lower curve by keeping a constant target room temperature 24/7.
It’s currently set to curve 20 and there are 6° outside; I’m watching the flow temperature shown on the boiler and I can see that the gas light comes on when it drops to 34°, then I can hear the flame being lit, and after about 10 seconds the temperature reaches 50°, which makes the gas cut off, then the cycle repeats.
It looks like the boiler is trying to keep the water at 45°, but cannot modulate low enough to keep the flame on, hence the continuous cycling.
P.S. The call for heat from Tado is currently constantly on and so is the pump