Vertical radiator

[emmkat]

I put on a vertical rad the other day and After clearing the airlock in The system got all rads going except this new one So I turned all the other radiators off And managed to get it hot. When I put the heating back to normal it was the only one that wouldn't heat. I tried Bleeding it And the return gets hot but the flow stays cold.

 

[MANDATE]

Sounds as if the new radiator is furthest away from pump and water will take the least line of resistance and prefers not to go that route, until you forced it by closing remaining radiators. So it could be a balancing issue.
You could close the lockshield valves a touch on the other radiators creating a little more resistance with a view to less resistance on the problem radiator.
On the other hand you may have a by-pass valve where the water can go to the return pipe in preference to a distant radiator.
Sometimes there is a gate valve on the pipe leaving the HW coil which acts as a lockshield. The purpose being to restrict the flow to HW on a fully pumped system so water has to go through the radiators.

I had a similar issue where balancing improved it, but did not fully solve it.
Finally removed pump to find the inlet and outlet ports were reduced in diameter from approx 20mm to approx 6mm. by sludge.
Opted for new pump and isolation valves. problem solved!

 

[emmkat]

Thank you but actually it is the closest one and is fed before it gets to 3 port valve.

 

[picasso]

You havent plumbed it in before the pump have you ?

 

[emmkat]

No it's after the pump but tees off before it gets to the port valve for the other rads.

 

[MANDATE]

Any particular reason why it's fed before the 3 port valve?
So with CH off and HW on it's active and with CH on and HW off it's active.
I'm a little puzzled what it's balanced against, the HW system or the other radiators?

 

[emmkat]

It's not my own place so it's how it was set up. But yes to ch and hot water and it used to have towel rail in its place which worked perfectly fine