scalding hot new Danfoss c-2 TRV cold lockshield and new radiator only hot at top .

[big john hog]

I have recently replaced all fourteen Stelrad radiators eight singles four doubles and two chrome towel radiators on small bore 10 mm piping in my four bedroom detached house.The Grundfoss pump is ten years old and sounds good .no bearing rumble.The Ideal classic ff 350 boiler is twenty years old but has been serviced regularly.Even when the balance has been turned down to a quarter of a turn on all the lock shield valves and the problem radiator furthest away has the lockshield fully open and with the pump on speed setting three .the radiator furthest away has a scalding hot Danfoss TRV and the lock shield remains cold.The system has been cleaned with F3 and flushed .The radiator has been removed from the wall and flushed manually and there was no sludge deposits in the radiator .Eventually after about an hour the radiator heats up and the valve lock shield valve is slightly warm.The boiler is set to three.My plumber has agreed to replace the pump with the new grundfoss ups3. In your professional opinion do you think that this will solve wot appears to be a pump problem .I have carried out the usual test of shutting down all the radiators and running the system .The radiator gets scalding hot together with both valves .Many thanks

 

[ShaunCorbs]

10mm isn’t the best they used to say 5m max run

 

[big john hog]

10mm isn’t the best they used to say 5m max run

Totally agree with you Shaun I am not a fan of it either. When the system is drained down the ground floor radiators have to be drained individually as they are the piped out of the wall type .My plumber uses a wet vac to do this before flushing rads individually.Many thanks for your expert time and professional advice Shaun thanks for everything

 

[ShaunCorbs]

Your more than welcome let us know the outcome please