The purpose of balancing a system is to keep all the rads at a fairly even temperature so that all rooms that need heat can be heated evenly. Balancing rads is only really an issue if you have some rads that dont heat up enough to warm up a room.
Radiators need water flowing through them at a specified rate and with a specified temperature drop to produce their rated output. If a radiator is not giving the correct output, the room will not reach the required temperature and the TRV will stay permanently open.
By reducing the flow to rads nearer the boiler there is more available for the ones further away.
It's not a matter of reducing the flow but of providing the correct flow. A 1kW radiator next to the pump needs exactly the same flow as a 1kW radiator furthest from the pump.
Simply having and using TRV's will take care of most of it
That's plumbers folklore! Why do you think so many people complain that the TRVs are not working? The system is not balanced correctly
- Turn boiler off and allow to cool
- Make sure HW is turned off
- Open all LS valves fully; remove all TRV heads and open all manual rad valves fully.
- Turn the boiler temp to max and bring system up to temperature.
- Check, by feel, the order in which the rads warm up and make a list.
- Adjust the bypass (if fitted) as per mfr instructions
- Measure the temperature differences between the flow and return pipes at the boiler. What it should be will depend on the boiler -refer to the installation manual. If the temperature is not right, you need to adjust you pump speed (higher speed gives smaller difference and vice versa). Set the speed to give as a difference as close to the mfrs recommendation as possible.
- Turn the boiler off.
- Close all lockshield valves. Leave TRV heads off.
- Restart boiler
- Attach the pipe thermometers to the first rad in the list made in step 5 and open the LS valve a quarter turn
- Wait until temperature has stabilised on the two thermometers. If the difference is smaller than that at the boiler, close the LS valve a fraction, or vice versa. Wait until the temp has stabilised and check again.
- When you are happy with the first rad, move on to the next on the list.
- Repeat steps 11, 12 and 13 for each rad on the list.
- When you have reached the last rad, check the boiler temp difference and adjust pump speed if necessary.
- Go back to the first rad and test it is still giving the correct difference
- And so on, going round and checking the temperature difference until they are all as near the required drop as you can make them. Don't expect perfection
- Replace TRV heads and set to required temperature
if you do not have clip on thermometers you can use an infrared thermometer (about £25 from Maplin)
A very small
change in the amount a LS valve is open can have a considerable effect on the temperature difference. Because of the way LS valve are constructed, it is virtually fully open when it is one and a half turns open. So most adjustment will be within one turn from closed.
If you find that the wall thermostat is turning the boiler off before the TRVs in the other rooms work, you should close the wheel valve slightly, so the rad gives out less heat and the room/hall warms up slower. It's a matter of trial and error.