no heat to replacement rad

[ccw123]

Morning,
I have just removed two 700mm square double convector rads from my living room and replaced then with a single 2000mm x 400mm double. The rad is in the same position as one of the old ones and uses the same, although modified, 15mm pipe, which is branched off 22mm.
I am getting no heat to the new rad, I've balanced the system and shut the bypass and the best I get is a warm, not hot, flow pipe up to the new rad. I've flushed the system twice and have even taken the valves back off to check they were working, which they are. Have I gone too big with the rad, it's btu value is approx 9500 or do I need to replace the 15mm with 22. It's doing my nut in can anybody suggest anything?
Thanks in advance,
Chris

 

[AlanE]

Air in one of the pipes feeding the radiator?

Close both valves, partially drain the rad. Now opern ONE valve and bleed until you cannot hear any air entering the radiator, close valve and bleed with other valve open.

Problem could be that you have air lock in one of the pipes and no amount of bleeding a radiator will shift it. Water takes the easy route and enters the radiator by that route. Both pipes need to be clear to get rad to work.

 

[tryitandsee]

Was the existing a flow and return (two pipe system). Did you accidently join the two flows or the two returns when making pipe adjustments.


Or have you used excessive solder and blocked pipe at a joint.

 

[namsag]

Its an airlock just turn heating on and turn all the rads off except 1 off the cold ones.
The air should then be pushed out after that one gets hot turn it off and turn the other cold one on once that gets hot turn the other one back on at same time leave till both hot then turn the rest back on

 

[sooey]

Its an airlock just turn heating on and turn all the rads off except 1 off the cold ones.
The air should then be pushed out after that one gets hot turn it off and turn the other cold one on once that gets hot turn the other one back on at same time leave till both hot then turn the rest back on

You forgot to tell him to add salt and pepper, still a good recipe though, how long does it take?

 

[namsag]

At gas mark 5 twenty minutes salt and pepper to individual taste

 

[gigz]

Check the rad did'nt have 2 plugs in one of the ends (those b*ggers in the factory think its funny)