Balancing a system with under/oversized rads

NobodyImportant · 08-01-2013 11:30AM #1

Hi all,

I’m changing the pump on my current OFCH system and will need to balance the system afterwards. I’ve bought my rad thermometers and learned about the 12 degree differential and how to balance them until you get this temperature difference.

My question is, does this method rely on the system have TRV’s and the correct BTU’s for a radiator?

I have some rads which are grossly under/oversized for the system, so say the first rad on the system is too big, if I balance this rad, it will be too hot. So can you balance rads AND lower the temp? If so, how? Do you just pull the intake and outflow down while still trying to get the 12 degrees?

Or stop being a cheapskate and put TRV’s on the oversized rads and have them set correctly?

Thanks.

deandean · 08-01-2013 11:59AM

It's about 12 degrees across the boiler IIRC; it's about 3 or 4 Degrees or even less across a radiator.

The oversized rads: close the lockshield completely and just crack it open half a turn. You'd be surprised at how much you need to throttle a large rad to reduce the output.

Undersized rads - nothing you can do except have the lockshield fully open.

TRVs only come into play when the room has reached the required temperature - this is separate to balancing.

Have fun!

Balancing a system with under/oversized rads

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