Rad balancing

[new2gas]

I have CH system to balance.

I have read the FAQ's for further help.

The standard advice is to open all rads to 1/4 turn.

Why don't you open the rads fully, and wind back to balance, if necessary?

Cheers for any help.

 

[flameport]

The idea is to get at least some flow to all of the radiators initially.

With all of them wide open, it's likely some wouldn't heat up at all.

 

[D_Hailsham]

The standard advice is to open all rads to 1/4 turn.

Why don't you open the rads fully, and wind back to balance, if necessary?

Two reasons:

1. The typical lockshield valve is full open at about 1 to 1½ turns from closed. As many LS valves can open over two turns from closed you will have to wind the LS valve in over a turn before it starts to have the slightest effect.

2. A quarter turn open is much closer to the required setting.

Don't forget that a 15mm pipe can carry about 6kW at a 11C differential, so if you are connecting a 1kW rad to 15mm pipe you need to reduce the flow rate to 1/6th of the open flow rate.

 

[Agile]

There is another reason.

Bit more difficult to explain though.

If the valves are well closed then the pump pressure will be higher.

A higher pump pressure will better send more flow through the highest resistance circuit.

In practice setting to just open 1/4 turn is very close to a reasonable setting and an installer could bit a boiler, commission it and then leave it working for a day or two and come back to do the final balancing having left a reasonably well working system.