New Rad not getting hot, single pipe CH system (partial)

[matt-l-p]

Hello, i've posted on here as it seems there are a few single pipe experts.

I've installed a big column rad with normal valves (no TRV) on a single pipe system, i have done this in 2 other rooms with good success and continue to get very hot. The rest of the house is on a 2 pipe system and works well.

When i converted the rest of the house to a 2 pipe system i couldn't do the remaining 3 rads on single pipe system as the rooms were completely finished with oak tongue and groove flooring and the rads were working well.

The rad i'm having an issue with has never worked great and i thought a big column rad might help, but it hasn't. The flow into the rad is getting really hot but there seems to be not much flow, after 2 hours it still isn't getting up to temperature.

I've found an old picture before i replaced the floor and subfloor and it looks like the 15mm return the the 1 pipe system is on a tee piece on a corner, i'll attach a picture.

could it be the water is just rushing past that tee piece as it's on the corner, so no flow for the rad?

Any help would be appreciated.
[automerge]1605860860[/automerge]
This is the current downstairs set up
[automerge]1605861133[/automerge]
Please see new proposal picture, would this work ok?

 

[Aquarius]

Quite possibly just a balancing issue, I’m not 100% with single pipe (not had the pleasure of working on them). Also, these column rads, not sure if there’s a certain way to hang like vertical ones and baffles?

 

[matt-l-p]

Thanks. It's a horizontal one, so doesn't need baffles.
I've tried shutting other radiators and made no difference, also tried for air locks.
Bit of a mystery, I think I could run in a plastic return pipe to the boiler without much damage to the oak floor, just wanted to make sure that would work.

 

[Gasmk1]

have you pipe top flow bottom return as single pipes use gravity flow for the rad

 

[matt-l-p]

No I've not tried that yet, I have 2 other column rads on the single pipe system and they work fine both piped on bottom.

 

[Last Plumber]

Where is the pump on the sketch?
Can you add it in?
How have you converted the rest of the house to two pipe? Can you draw a sketch of that?

 

[matt-l-p]

Where is the pump on the sketch?
Can you add it in?
How have you converted the rest of the house to two pipe? Can you draw a sketch of that?

It does have a pump just after the boiler outlet, then tees off one feed upstairs and downstairs, then the return from upstairs taps into the return to the boiler

 

[exedon2]

I first fixed many hundreds of one pipe systems in early 70s ( council upgrades) rad connection was always T on branch. So your layout with connection on end is not ideal so probably why it's never been great.
Should also mention lots of horizontal column have baffles!

 

[matt-l-p]

Thanks , much appreciated. It must be the Tee on the corner. Is a baffle the same as a diverter. The instructions says only use them on rads over 1000mm high, so I didn't put them in

 

[exedon2]

Maybe just check with rad manufacturer re diverter on a one pipe?
I've installed this type of rad as a heat leak and manufacturer said diverter was needed . Remember on a one pipe heat goes into rad by gravity.
One more thing your rad valves are full bore? I've seen some that are really quiet restrictive.

 

[matt-l-p]

I will check with them thanks, yes the valves are full bore. I think running the return pipe to the boiler will solve it