Flow and Return Temperatures

[Possom]

If the temperature is taken at the lockshield and the TRV for a radiator, I have heard that the temperature difference should be in the range of 10 - 12 C. However, which should have the higher temperature or the lower temperature?

I'm currently getting a difference between the two of about 2.5 C with the lockshield being the hotter of the two.

Thanks.

 

[oldbuffer]

1. The temperature difference between flow and return measured at the radiator valves should be:
1a. 10 - 12 degrees C for a system with a non-condensing boiler.
1b. Around 20 degrees for a system with a condensing boiler which has had radiators sized for lower water temperatures.
1c. If you have a condensing boiler, but the system has been sized for a non-condensing boiler, better to go with a 10 to 12 degree difference.
2. These days the TRV is not necessarily on the flow end, as most are bi-directional so it doesn't matter.
3. Whichever end gets hot first is the flow end.
4. 2.5 degrees isn't enough and suggest the water is going through too quickly. Close the lock shield (no matter which end it is on) to make the water stay in the radiator longer and give up more heat.
5. Always count the number of 1/8th turns required to fully close the lock shield so that you have a record of where to return it if you make a mess of the balancing.