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Showing results for tags 'boiler modulation'.
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I have mentioned here before that our Viessmann Vitodens 200W 35Kw system boiler occasionally loses pressure. It happens every 8 weeks or so. @Nickfromwales recommended flushing the system with a special sealant and I’ve asked my installer to do this… still waiting. Yesterday night the boiler recorded a low pressure fault at 1124pm. We didn’t notice till 9am this morning when we woke up and realised we’re had no heating and the hot water was warm. I’ve topped up the pressure to 2.1, and this caused the boiler to start firing up again. I noticed that the flow temp slowly went up from 20C to 65C, it took about 10 minutes to get there. I also noticed that the modulation of the boiler was 98% to 100%. This has slowly come down to 55% as the boiler has been running over the last 40 minutes or so, but that is still much too high for normal. Even with every UFH zone on and our 2 rads and HW switched on, the boiler doesn’t go over 50%. At the moment, wet only have the HW, the two towel rads and about half the UFH on. Am I just being impatient, and will the modulation fall to around 35 or 40% eventually, which is where I’d expect it to be for this level of demand? Can anyone explain why this is happening Is it to do with the boiler running less efficiently until the whole system pressure is balanced?
