Cold radiator

[Spud3006]

Just finished my extension in time for Xmas however the radiator in the new lounge is cold.
I am an electrician and installed the new pipework etc with help from a friend who is a kitchen fitter and has a much better knowledge of plumbing than myself.
As different sections of the extention were completed and rooms decorated the various radiators have been installed and brought into use without any major problems.
After completing the final room ( the lounge) the radiator has been installed with a trv and lockshield.
I have bled the radiator of any air and the radiator became hot for a short period of time whilst the hot water was pulled into the radiator.
I have turned all the other radiators off at both ends leaving just the one radiator on at both ends and put the heating on full blast and managed to get the lounge radiator pipework leading up to the trv hot.
All the radiators in the house are brand new and the boiler is a brand new valliant ecotec pro 28 with magnaclean.
The radiator in the lounge is fed with 10mm pipe reduced down from 22mm.
All flooring is down upstairs and carpeted and ceilings up and artexed in the lounge.
I'm starting to think its something my friend has done but don't want to ask for his help for personal reasons.
Can anyone help please.
Just to add an extra problem to the mix I also installed a hep20 underfloor heating kit on to the heating system a couple of years ago where I removed a radiator in the kitchen and extended the 15mm flow and return pipes into the conservatory via a recessed wall mounted trv and have only ever managed to get it hot once.
Since then the extension has been built and now it's finished these two problems need sorting.[/b][/list]

 

[ChrisR]

Either
TRV is stuck shut - remove the head, the pin should "bounce" up and down it you tap it with something like a screwdriver handle

or
Both ends of the rad are connected to the same side of the heating - same potential, like..

or, um
TRV is a funny one which shuts if it's the "wrong way" round. I've had that on supposedly bidirectional trvs

or another one way valve somewhere

Or cheapie lockshields can jam shut and shear off

All I can think of!

---

Turn off rad, Drain it. make sure water comes out of both valves.

 

[Spud3006]

Either
TRV is stuck shut - remove the head, the pin should "bounce" up and down it you tap it with something like a screwdriver handle

I have tried this a couple of times and the trv works fine.

or
Both ends of the rad are connected to the same side of the heating - same potential, like..

I think this may be the case. (looks like spuds taking the new flooring up today!!)

or, um
TRV is a funny one which shuts if it's the "wrong way" round. I've had that on supposedly bidirectional trvs

They are Drayton trv4's

or another one way valve somewhere

All are Drayton trv4's

Or cheapie lockshields can jam shut and shear off

I have used cheapish lockshields

All I can think of!

---

Turn off rad, Drain it. make sure water comes out of both valves.

I have done this before and water comes out both valves

Thanks very much for your help and happy new year