Radiator balancing

[brickland04]

If I need to balance my system, I have read that you need to work your way round the system and put clip on radiator thermometers on the in and out pipes of the radiator and ensure that the temperature difference is correct. I have had a look on quite a few websites for the clip on thermometers but can't find any. Where can I purchase these from, or is there an alternative to using the clip on ones ?

 

[chrishutt]

Just use your hand to judge the relative temperatures - it's good enough even for most professionals! Once the system has settled down (with all TRVs fully open) the flow pipe connections should all be the same temp (too hot to hold) but the return pipes will vary. The aim is to get all return temps about the same and slightly cooler than flow. It should be easier to judge relative temps if you set the boiler flow temp fairly low (say 40C or as low as the dial will allow).

 

[brickland04]

So if I find that all the flow pipe connections are not the same temp (too hot to hold), I should then reduce the return flows on the hot ones so that the cooler flow pipe connections will then get the heat ? If I have a radiator that when the system is up and running the return flow pipe is always hooter than the flow pipe, could this mean that the TRV has been fitted to the wrong end ?

 

[chrishutt]

the return flow pipe is always hooter than the flow pipe

This is not possible. The hotter pipe is the flow pipe, the cooler pipe the return pipe.

I should then reduce the return flows on the hot ones so that the cooler flow pipe connections will then get the heat ?

No, you're getting muddled between flow and return. Read my post again - you are comparing the return pipe temperatures. Those that feel hotter will need restricting until all return pipes are about the same temp.

 

[brickland04]

I understand the principle of the flow and return pipe temperatures and this is true for all of my radiators except one. The one in question has a lower temperature at the TRV end, even when the TRV is fully open. This is why I thought the TRV might be on the wrong end. I have Drayton TRV4 on it. Would it be worth me swapping the top part of the valve with one off the other radiators that I know is working OK ?

 

[chrishutt]

Most modern TRVs are bi-directional, so they can be fitted in either orientation (horizontal or vertical) at either end of rad. Look for arrows on valve body.

 

[jobloggs]

Quite a lot of TVRs are now bidirectional and can be situated on either the flow (inlet) or return (outlet) side of the radiator. If yours is on the cooler pipe it just means that it is on the return and will function OK unless it is a one directional type. If these are fitted wrongly then they can be noisy

I think that Drayton TRV4 elbow and straight types are both bidirectional.

 

[ChrisR]

I start with small rads near the pump open just 1/4 turn, big ones near pump 1/2 turn, going further open as you move away from the pump. One full turn open is pretty much full open.
It's surprising how little flow is needed per rad . Errm,
10º temp difference, 1kW, 1.4 litres/min. 12seconds per mug. I used to be able to pee faster than that!