i cannot get a radiator to get hot. The top of the radiator is lukewarm (bottom cold)and if both valves are open the inlet pipe connecting the valve to the system gets hot. If this valve is closed then the pipe to the other valve gets hot.
Sounds like a build up of sludge (if this is an old rad), may need to come of and be hosed out. If this is a new install, not sure.
If this is a single pipe system then it sounds as though there is not enough pressure differential across the radiator to initiate a flow. Do the feeds to the radiator tee out from the flow pipe or does the flow just go in/out of the radiator?
Daddy Sparky's questions raise more important points that should be considered. How is your central heating system configured? If the system has been installed or added to with this rad. on a feed-in feed-out to each rad. in turn (going through each rad. in the circuit first) and this rad. is the last in the circuit, getting it hot will be difficult and this is where (I believe) balancing is required. Does this make sense. If I'm wrong, please say so!
Daddy Sparks I have tried closing all the other radiators on the system and the situation is still the same (is this the same as balancing?). How do I create a pressure differntial across the radiator? is a possible option to feed into the top of the radiator and take off at the bottom as in hospitals or is there another way a more powerful pump perhaps?