New central heating system, radiators cold at the bottom & hot on top

[panlondon]

Hi, we have a new megaflo type system installed. Bosch system boiler ground floor, cylinder in the first floor. I appreciate that it may take a while to heat up the system from cold and the house eventually gets warm. However, I have noticed that most of the radiators are cooler at the bottom and warmer at the top. I have bled the radiators etc but no improvement. All radiators are double. There is also an underfloor system running independently (through the same boiler). Boiler is 27kw capacity and cylinder 300L.

I have read that cooler at the bottom could be a symptom of sludge but this is a new system with new radiators. Any ideas what might be wrong? Pressure looks normal and hot water is good btw. Thanks very much.

 

[ianmcd]

wont be sludge on a new system, the system needs balancing, get the installer back

 

[vulcancontinental]

Probably balancing, are some ok and others not but how new is new? How much of a difference is there across the radiators, they'll always be some as hotter water rises to the top. What made you check, are you not warm enough in all the rooms or only in some?

 

[dilalio]

Close TRVs (manual valves) on all but 1 of the problem rads, this should now get raging hot; close the TRV on that and open up one on another problem rad, this should now get raging hot.

Open up all TRVs again and wait for 20 mins then crank down the lockshield valves on the hottest rads by a full turn or 2. A bit of experimenting and you should be able to persuade flow away from the hotter rads (without affecting their performance) to the cooler rads... Thus balancing the system.

Call the installer back if you have no joy but it's good to learn how to do this, for future upgrades and decorating projects.

Edit: oh, and open up the lockshields by a turn or 2 on the cooler rads, as you close down the hotter ones... You can find much better online guides on balancing, than I've put here

 

[jeff the gasman]

Probably lockshield cracked open, never commissioned properly or bypass fully open.