TRV Puzzling problem

[dougie212]

I have had a few issues recently with my boiler (see my previous threads) but the one which is niggling me most is a trv I have fitted onto a new radiator. Essentially, I have replaced an old radiator with a new slightly larger radiator. The old one worked perfectly. When the heating kicks in the lower part of the radiator and the TRV remain cool. Now, according to the box it is a bi-directional trv so I have it located on the right hand side of the rad for easier access. I have tried the following so far :

- isolated the new rad and put the heating on. Eventually the bottom of the rad and the pipe gets warm but I think that is more heat spreading rather than hot water flowing through. It's not proper hot.

- isolated the new rad and flushed through using the filling loop and a hose on my drain valve. I did get an escape of air and black muck come out.

- undone the trv nut and drained the radiator. I then put a bucket under the trv and turned it on. Water flowed but I am aware that the water flowing into my bucket was actually flowing the wrong way when its attached onto the radiator.

- I have put a cleaner in but that had to be drained out due to the pump stopping and air building up in the boiler.. my intention is to put another cleaner in in the hope the trv issue is sludge. On that note what brands do people use?? I did try the no nonsense from screwfix but wondered what other peoples experiences were.

I have tried pressing the pin down on the trv and it does move, and with the heating on, I have tried pressing the pin down and releasing a few times but no flow.

Could it be possible my bi directional valve is not bi directional or the bi directional feature isn't working, I'm almost tempted to switch the trv and lock shield round and see what happens.

Does anyone have any more ideas I could try please? Many thanks

 

[Last Plumber]

Few questions!
Is the rad hot at the top ?
Did you oversize it for the room ?
If you did and it's a double panel it may just be that the room is warming up and the TRV is doing its job !
Double rads tend to warm top first. IME.

 

[dougie212]

Hi there..

Thanks for your reply. The rad is hot at the top... and cool at the bottom getting cooler towards the TRV. I have also lifted the floorboards and the pipe leading away from the TRV is cold. The rad is in our landing upstairs, the previous rad was tiny so I have just increased its size a little to get a better spread of warmth, but its still only a single panel.

 

[Last Plumber]

Sounds like slow flow.
Is this a two pipe system ?
Is the lock shield ( other end ) open ?

 

[dougie212]

It is, and yes, the lockshield is fully open. Could it be possible that there is a blockage in the radiator itself?

 

[Last Plumber]

It's possible. More likely in pipework but if the last rad worked well I think it unlikely.

What size is the pipe work and what size is the rad ?

Length hieght etc

 

[Sharp Point]

Is the system a one or two pipe system?

 

[dougie212]

Its a two pipe system bogrodder. The pipe is 15mm and the rad is 600 x 1000 single panel

 

[dougie212]

I have managed to feel the pipework under the floorboards. The pipe to the rad is hot.. the lockshield is hot..(i know it should be the other way round, but the trv is best accessible on the other side)... the rad is then hot at the top... cool at the bottom.. the trv valve is cool as is the pipe away from the trv... the pipe in which it returns to is hot

 

[joni os]

Fully open lockshield valve, remove head of TRV, close down all other rads and towel rail, then with room stat. set high see what happens after 30 mins heating. Vent air from rad as necessary.
Water flowing," wrong way" from TRV. Because of pressure in system. water will flow out of any open end.

 

[dougie212]

Thanks Joni...Is that with a view of clearing a blockage?

 

[gassafe]

Hot at the top & cooler at the bottom sounds like most rads iv ever touched...

 

[dougie212]

Ok.. by cooler... I mean cold..

 

[tamz]

Nothing to do with which pipe trv it is fitted to. It will open just the same. Bi directional valves (allegedly) don't knock when closing when fitted to the return tho the cheap ones still do.
Your problem is caused by lack of flow.

 

[Darren Jackson]

Hi, what setting is the pump on, can you ramp it up a notch and re balance the system?