ive been trying to balance my rads to DT5 but didnt realise it needs to be when the heat pump is flat out. so now im wondering if i should just try and match the DT the heat pump is aiming for at the time im doing the balancing?
at the moment im just using a pair of digital temperature displays on the flow and return of the radiator.
Some advice in this thread: Radiator Balancing - is there an idiots guide?
…but heed this warning in post #15:
Obviously from a heat pump point of view, as I’ve found to my cost, you need to ensure there is enough flow going through the rads to ensure you have enough working system volume in the system.
I’d throttled down my rads so bad chasing DT5 across the tails I’d restricted by working volume to barely nothing.
My COP has shot up this last week since opening the rads up. I’ve now given the heat pump more system volume to work with. So excuse the pun, but there is a balance to be had here.
So, it may be better to keep all rads open and only balance them a little if needed; i.e. some rads or rooms aren’t getting warm enough, and some flow needs to be redirected.
Yeah I started with all my rads wide open on both valves and still found they all warmed up, but cop was bad and I felt maybe the hp was cycling due to water short circuiting back to the hp too quickly. Maybe the best idea is to target dt2.5 as that seems to be what the hp tries to do during +5c sort of days.
My approach was to throttle the rad closest to the primaries. I did this for two reasons, 1) the radiator in the attic was not heating so the flow reduction on one other rad was sufficient to make that work and 2) the DT on that rad closest to the primaries was like 2 or 3c or something when measured with a laser thermometer and may have been causing cycling similar to your thoughts.
It turns out that all my problems were really elsewhere, the automatic bypass valve has been installed by the incompetent OES and left fully open! So check your ABV is also set correctly.
i dot seem to have an ABV, should i have?