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]

Is this the only problem radiator?

 

[cjg]

try re balancing your c/h

 

[big john hog]

Is this the only problem radiator?

Yes all the others are scalding hot

 

[ShaunCorbs]

What happens if you shut half of your working rads via the trvs ?

 

[big john hog]

try re balancing your c/h

Many thanks .How do you mean by re balance

 

[big john hog]

What happens if you shut half of your working rads via the trvs ?

I have seven rads upstairs only four have trv valves seven down stairs four with trv valves

 

[ShaunCorbs]

Turn the 4 off down stairs does the problem rad heat up

 

[big john hog]

Turn the 4 off down stairs does the problem rad heat up

Just turned four trvs off downstairs including the problem rad one which has a trv on it and its scalding hot

 

[ShaunCorbs]

Leave the problem rad open / calling

 

[big john hog]

Just turned four trvs off downstairs including the problem rad one which has a trv on it and its scalding hot

Correction just checked again and problem rad starting to go cold

 

[big john hog]

Leave the problem rad open / calling

ok I will run down stairs and open trv

 

[big john hog]

ok I will run down stairs and open trv

Problem radiator now getting hot

 

[ShaunCorbs]

Fully hot / acceptable?

You either have a balancing problem or pump is weak

 

[ShaunCorbs]

RAS-B2

Danfoss radiator thermostats maintain constant desired room temperatures, individually room by room. The RAS-B2 is a 2-in-1 temperature control and automatic balancing valve, combining a thermostatic radiator valve and pressure controller for two-pipe heating systems.

www.danfoss.com