DIY Doctor UK DIY Forums

I've just had a new radiator and TRV installed by professional gas engineers on the top floor bathroom of a 3 storey house.
However when the TRV is set to 5, the maximum setting, the new radiator only heats up to about 40% of the heat on the other radiators and only 40% of the heat it used to be on the old radiator that it replaced. It is also much slower to heat up than the other radiators and I have noticed that it heats up the bottom half of the radiator first and only much later heats up the top half.
Secondly, the same professional gas engineers installed a new TRV on an old radiator in a middle floor bedroom, but after installation it now only produces about 60% of the heat that the other radiators do and about 70% of the heat it used to before the new TRV was installed when the TRV is set on 5 which is the top setting.
What could be causing these 2 problems? Are these likely to be minor problems are they major problems which are expensive to fix.
Sorry I can't upload pics because it says they are too big.

Thanks.

Hi jogey,
Most likely cause is that you need to bleed the radiators, if you have a sealed system you may have to top it up as you do this.
Failing that get the installers back.
Regards S

After bleeding the radiators worked fine. Thanks Stoneyboy