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

 

[big john hog]

I would have a look in the loft when it’s on speed 3 make sure it’s not coming back over via the vent

have just checked F.E tank in loft with ch running and pump on 3 .The water level is about 2 inches below vent. Not noticed any water coming out of over flow pipe outside house .Also ball valve not dripping

 

[ShaunCorbs]

Sounds like it’s ok maybe turn all the close lockshield valves shut and open them 1/4 a turn then go further away 2/4 etc till your at the furthest away which is fully open

 

[big john hog]

Sounds like it’s ok maybe turn all the close lockshield valves shut and open them 1/4 a turn then go further away 2/4 etc till your at the furthest away which is fully open

I have opened the lock shield valves as you have said in stepped increments .Still no luck.The top of the rad stays hot but takes ages to get hot all over but only if lockshields are open quarter of a turn on all of them and furthest away lockshield fully open pump on three only if the boiler is on say 5.5 .How about the non lockshield side wheelhead valves I have them fully open

 

[ShaunCorbs]

I have opened the lock shield valves as you have said in stepped increments .Still no luck.The top of the rad stays hot but takes ages to get hot all over but only if lockshields are open quarter of a turn on all of them and furthest away lockshield fully open pump on three only if the boiler is on say 5.5 .How about the non lockshield side wheelhead valves I have them fully open

The non lockshield side eg trv side should be fully open eg highest

 

[big john hog]

The non lockshield side eg trv side should be fully open eg highest

Yes Shaun they are .I have just set all upstairs and downstairs lockshield to quarter of a turn open and the radiator furthest away lockshield fully open and the rad does get very hot .Not until the boiler is put on the winter running setting of 5.5 as recommended in the ideale ff350 user manual does the lockshield go from luke warm to very hot.I think that this is the best that I can expect from the system.Maybe the radiator upgrade on the small bore 10mm plumbing is at the highest btu rating for the pipe work /boiler or maybe its just always been like it .

 

[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