DIY Doctor UK DIY Forums

I've spent all day trying to balance radiators but with unsatisfactory results. Sealed system combi boiler. Mixture of 15mm & 10mm pipework. Mostly old rads. Rads are all full & pump seems to be working. With some of the rads it's not totally clear which is the flow & return (valve tops have gone awol) so I've taken best guesses that the first to heat up is the flow. I can only seem to get some working to the detriment of others. I can get hot water flowing to all of them and I can get them working individually by turning all others off, and I can get sections (upstairs or downstairs) working ok. But when I try to balance them all together it goes pear shaped. Some rads have scalding hot flow & return pipes but patchy heat in radiator. Nightmare! Any ideas?

What prompted you to start this? Was there a problem?
I trust you know that there are (generally) 2 valves to each radiator, and (generally) the valve with the hand control knob on is (generally) the flow.
The valve on the return is a similar valve with a plain cover which sometimes locks the square on the shaft to prevent fiddling by children and grannies.

Starting from scratch, I think the best action is to turn both valves on all rads fully on or open, and run the system.

It may stretch your boiler, but all rads should get hot. Make a note of the sequence in which they heat up. The rad that heats up first should be throttled back by gradually closing the lock shield valve. Do not touch the control valve. Try fully closed and then open half a turn. Move on through the house.

I'm not sure of your skill, but if you require clarification, come back.

Grandad.

The promp was: 2 single rads (in one room, fed from above on 10mm pipes dropped from above) never worked properly so I removed them, capped the pipes & ran 15mm from nearest downstairs flow & return pipes to a new double convector to replace the two removed. I've gone through all the standard balancing process you describe but have been unable to get them all to work satisfactorily. Could it be a pipework problem?

The 2 rads which were giving trouble - are they on ground floor or first floor? Obviously I don't know your house, but it is pretty general practice for plumbers/engineers to run all the circuit pipework around the house inside the first floor void, taking short runs up to bedroom rads and longer drops down to ground floor rads. This makes life easy for them, but means you cannot isolate floors and control them individually.
If you have connected to your ground floor rads with 15mm pipe, were they already connected by 15mm pipe? Usually it is either 10mm or 15mm, and not mixed.
Maybe you have a system where your ground floor rads are on a seperate circuit (good), but if so, you have now mixed them up.
Personally, I have an unresolved circulation problem with 10mm pipework into a conservatory and have completely failed to find a small booster pump, and I have searched the net thoroughly.

Grandad.

The original troublesome rads were on 10mm drops down to ground floor. I took these off & capped drop pipes. The neighboring room has 15mm pipes dropping to feed two rads. I ran my new rad pipes (15mm) to connect into these. There's no separate circuit downstairs. Where originally I had 3 drops (2@10mm & 1@15mm) to 4 radiators, I now have 1 drop (15mm) for three rads. The only 10mm fed rad left is one in a bedroom.