In an ideal world you’d have the output of the rads match the heat loss of the room. This is what I’ve tried to achieve with my rad upgrades. So that if I put the correct calculated flow rate through the rads, all the rooms in the house should be balanced.
But we know this isn’t always the case in a lot of installs. There will be imbalances in heat loss and rad output.
But I still think you start by aiming to get the correct flow through each rad and then you adjust up or down whether you want more or less heat from the rad.
As Heat Geek told me this week, you’re ultimately balancing room temperature.
No own really cares about flow/return or MWT of the rad. The just want warm and balanced rooms.
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.
- Enough system volume to allow the heat pump to thrive
- Rads closed down enough to ensure resistance so that all the rads in the circuit get some heat
- The rooms across the whole house are balanced with enough heat being emitted
Obviously, there could be challenges with undersized pipework like @HydroSam has above.
And as Marko days, the underlying pipework adds complexity to the party.
Does that help?