Another one cold radiator problem

[pvcpro]

Hello,

One of my radiators isn't getting hot, when I turn off one of the other radiators it does get hot but this still leaves me with one cold rad.
It's the furthest rad from the boiler, it was the last to be added to the system when I did part of my ongoing renovation a couple of years ago.

Any ideas?

Thanks for taking time to read

 

[45yearsagasman]

Undersized pipework and system balancing for starters. How and where did you connect the last rad to the system. Size of rad and pipe size used.

 

[pvcpro]

It's a 1400mm K2 rad on 15mm pipes.
It's at the far rear of the property and is the end of a run, it doesn't return back to the boiler, it's on a loop of 3 rads and 1 towel warmer. This loop returns back to a manifold under the floor in the hallway.
The manifold is in 10mm as is the rest of the pipework back to the boiler, this was installed when we first moved here 9 years ago and I kick myself now that I didn't specify 15mm pipes but I wasn't clued up
about plumbing at all then, not that I'm an expert now but I at least know that much!