New Radiator lukewarm

[minermick]

Any tips on this would be welcome please.
In the summer my son and his wife had a radiator installed in their conservatory which, now they have come to use it gets lukewarm at best.
The top of the rad gets lukewarm as does one of the 15mm pipes connected to the rad (I presume the flow) but the second pipe stays cold.
The installer tee-d off the 10mm pipework inside the house for the flow and return but used 15mm pipe. Could this be a possible cause of the rad not heating up?

My diy experience of heating matters doesn't extend this far and any tips from you experts would be welcome.

 

[Dan Robinson]

Installer was an a7se.

 

[Dan Robinson]

Should tee from the main circulation pipework.

 

[minermick]

Thanks for the replies. It is tee`d from the main pipework which is 10mm and then goes through the wall into the conservatory and I wondered if it being tee`d into 15mm pipe this may be the problem ?

 

[FiremanT]

The 10mm won't be the "main" pipework. There will be a 15/22 mm ccircuit with 10mm taken from it, or a circuit to a manifold, with 10mm offtakes.