Hi
@JC22024 again. I've been reading through a printed-out copy of this thread and regarding post #92, I feel a need to correct your misunderstanding of how smart pumps generally work. A proportional pressure pump (including Grundfos Autoadapt) seeks to keep the pressure drop constant across the radiators. It very slightly drops the pressure as TRVs close to try to compensate for the decreased pressure losses across the boiler primaries (so there is some truth in your understanding) but one TRV shutting should not cause other radiators to fall dead. It does not drop the pressure very much. Conversely, a 'dumb' pump cannot help but increase its pressure as TRVs throttle down, thus forcing more flow through any TRVs that remain partially open, sometime resulting in whistling. They (smart pumps) aren't without issues, particularly as the conventional automatic bypass valves often fitted to heating systems rely on an increase in pressure to open up as TRVs are shutting down.
Constant pressure will keep the pressure constant across the boiler (but not compensate for the primaries: that's the difference, plus CP is usually a much higher pressure setting).
The way most smart pumps do this is by monitoring power consumption to get an idea of how much drag is being created and then varying the speed of the impeller. Unlike the older pumps which ran at a fixed speed.
I've balanced my own house before and after replacing a pump. The new pump has proportional pressure and I thought I'd give it a go. It actually made balancing MUCH easier as, when I throttled back one radiator, that didn't then result in an increase in pressure and hence flow to the remaining radiators. So instead of going around the house several times tweaking as I went, I only really needed a couple of passes.
Re post #152, I wonder if you could help me follow your explanation better? Please let me know if I follow your understanding correctly or not... you say you think the Vector BEM works by allowing the boiler to first run to temp [i.e. until the boiler cuts out on its internal thermostat?] and then, [when the boiler decides to re-fire?] slightly delays [the next firing up of the boiler?] and then continues doing this while also monitoring the run time and stat call time? Which stat are we discussing? Room stat, I assume?
Are you saying that your understanding is that the BEM is monitoring the boiler duty cycle and delaying the boiler from firing for progressively longer times until it notices that this is reducing the system's ability to get the room temperature up to the required temperature? I'm struggling to get my head around how this works, but it would be interesting to be able to do so.
Thank you.