Radiator cold at bottom

[m0t]

I took my living room radiator off to decorste behind it and as far as I know it was working fine.

This involved draining the system because one of the valves had failed. I replaced the failed valve with a Drayton TRV and changed the other valve for good measure.

I connected the rad back up yesterday and emptied a tube of Fernox F1 superconcentrate into the rad before reconnecting it and filling with water.

I noticed this evening that the rad was only getting hot along the two sides and along the top inch. I turned all the other rads off and tried it with the TRV disconnected and this caused the rad to heat up, although it was slightly cooler at the bottom.

Any ideas what could have gone wrong here? I would have expected sludge but we haven't had a problem until it was taken off.

 

[MeldrewsMate]

This is symptomatic of poor circulator (pump) performance.
Did you find sludge in the radiator you took off? If so the chances are sludge from other rads will have been dislodged during the draindown & refilling, and now has a new home in the pump.
I suggest you dismantle the pump and inspect/ clean the impellor slots.
Then trace and remove any airlocks so that the pump has only water to pump, they are notoriously bad at pumping air!

Consider fitting a magnetic filter to the system (Magnaclean, Fernox TF1, etc)

 

[m0t]

I have a magnetic filter - I guess my first check should be on this to see if it is blocked?

 

[m0t]

Right - removed the filter and it had a small amount of sludge in, but not huge. It was on the magnet but only covered about 10% of it at most.

I shall take the rad off later and report back, hopefully it is full of sludge because I need to problem fixed before Monday when the carpet fitters come.

 

[m0t]

Took the rad off and got a load of black water out of it. Took it outside and ran a hose through it until the water ran clear. It is a little better but still not right.