Originally posted by killa47
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To some degree I think this is inevitable on the Honeywell system if you have all radiators controlled (eg no bypass radiator left open) because under some conditions it will run the boiler when the HR92's are hardly open, but when it does that it generally runs the boiler at a low duty cycle. (Eg it may be turning it on for 2 minutes out of 10 minutes) But that may still be enough to trigger the "Gradient Limitation" warning on your boiler during that 2 minute period.
I have an ancient conventional boiler that has no electronics at all apart from a retrofitted digital flow temperature controller I added to replace the original mechanical flow stat - and I see the same rapid rise of flow temperature when for example there are only 2 zones in the house active and they are already up to temperature - but my boiler doesn't care, the flow temperature controller just shuts it off when it reaches the the target temperature and doesn't complain about the rapid rise.
The issue here really is that your boiler is being too clever for its own good - a fast flow temperature rise when all the radiators are nearly closed and the ABV is flowing heavily is to be expected. Does it actually cause a lockout situation where you have to manually reset it to get things working again, or does it just complain on the screen but continue working normally ? If the latter I probably wouldn't worry about it to be honest, if it does prevent it working I would see if there was any way to relax the "Gradient Limitation" threshold so that it doesn't get tripped.
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