I'm at my wits end with this one. The newest radiator in my house is a mid sized double rad, downstairs in the living room. When my Vokera 28 boiler central heating temperature is set mid-way (or 'Auto' as it states) all my rads are nice and warm except my living room one. The feed pipe, which has the lockshield valve (fully opened) is roasting but the heat is not transferring fully to the rad. The top gets, at best, lukewarm and the bottom stays cold. The return pipe, which has a trv fitted on it (fully functional, pin ok and flow indicator set in the right direction). When I turn the temperature to maximum at my boiler, the rad does heat up a good deal more but it is only at the top. The return pipe remains as cold. Does anyone have any ideas? Much appreciated.