Hi, just an observation, I've noticed that when I'm sat in my home office with just the office radiator on (evohome shuts down the rest of the house during the day) my boiler can't seem to modulate down low enough. I have a bypass rad in the bathroom, so only have 2 "active" radiators when I'm working in the office. However when the boiler is indicating it's lowest flame height, I can see the flow temperature slowly rising up on the boiler display until eventually it hits 78 degrees and cuts out - if I run up to the airing cupboard I can see that the pump is still running so looks like the boiler is cutting out due to excessive flow temperature. I can watch the displayed temperature then fall quite quickly as water continues to circulate, and a few minutes later the boiler fires and the same thing happens again, after a few minutes it cuts out again and so on.
I've got a Viessman Vitodens 100 and I think I read the minimum output is around 6kw, I also read that they've produced a newer version with an even lower output, but my boiler is 3 years old which is before this new one came out. So I'm wondering if there's anything I can do - should I open the TRV on another radiator and effectively have a second bypass rad, or just not worry about this - I'm not sure if it's more efficient to keep the boiler fired on minimum flame height or allow it to cycle like this, I don't know what uses more gas because when it fires it does not fire at minimum flame height, it starts off a bit higher as you can hear the fan spin up and then slowly it slows down as the boiler settles into "minimum" mode, so there is a period during the ignition phase that it might be using more gas then if it were continuously running at it's lowest flame height.
Anyone got any thoughts?
I've got a Viessman Vitodens 100 and I think I read the minimum output is around 6kw, I also read that they've produced a newer version with an even lower output, but my boiler is 3 years old which is before this new one came out. So I'm wondering if there's anything I can do - should I open the TRV on another radiator and effectively have a second bypass rad, or just not worry about this - I'm not sure if it's more efficient to keep the boiler fired on minimum flame height or allow it to cycle like this, I don't know what uses more gas because when it fires it does not fire at minimum flame height, it starts off a bit higher as you can hear the fan spin up and then slowly it slows down as the boiler settles into "minimum" mode, so there is a period during the ignition phase that it might be using more gas then if it were continuously running at it's lowest flame height.
Anyone got any thoughts?
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