Double Trouble Radiators

Hello,

I’m after some advice. I swapped 5 radiators in our home, 3 upstairs to new single panel ones and 2 downstairs to double panel ones.

The rads upstairs and downstairs get very hot except the 2 new double panel rads. The flow pipe gets very hot but the return pipes are just cold. The biggest one of the 2 gets very hot at the top but cold at the bottom.

I’ve taken one off the wall and blaster a hose through it and the water was black for about 2 seconds. I’m starting to run out of things that it could be or things that I could try. All radiators have been bled and now only water comes out. I’ve attempted DIY balancing and it did improve the 2 but still cold at the bottom and return.

P.s return pipe to boiler is just as hot as the flow out of the boiler.

many advice would be amazing thank you.

 

turn off the hot ones.

what do the cold ones do?

do you know how to do a chemical clean?

photos of the valves at both ends of your rads may help.

 

Some of those radiators are particular about which side is connected to the flow.

Did you follow the instructions in this regard?

 

I turned off all the radiators that get hot except these 2. After this, they did get slightly warmer but not hot all over and the return only got slightly warm. Has both PTFE tap on olive and thread and I made sure the tape wasn’t covering the hole.

 

You may need to take the rads off and then open the return valve and see if you have proper flow from it, they may be restricted further downstream.

Do have to say they're awful low on the wall. Also PTFE tape isn't used on the threads/unions of the connections only on the olives. With the unions just clean up the mating faces with a green scouring pad.

 

I just placed it in the same place as the last one, the pipe connecting the radiator to the pipe through the floor was dry short so I wasn’t able to get much PTFE tape on there so I doubled up on the thread also.

the one in the picture I took it off and then opened the valves black water came out at first but they both ran clean after that.

 

Which boiler and pump are fitted ?
Have you looked at pipe work under the floor. You may have a "One pipe" system.

 

We have Worcester Greenstar 24i. No idea about the pump. It’s a one pipe system I know that much. The one pipe that runs through the house is hot throughout

 

The TRV will severely restrict flow on a 1 pipe.
Special full flow valves were used.
In my experience very few systems on small bore worked properly.
Try changing the TRV for a standard rad valve (Full bore).

 

Do you have universal TRVs?

 

I just used the TRV that came with the radiators which was these.

https://www.screwfix.com/p/drayton-rt212-white-chrome-angled-trv-lockshield-15mm-x/679hg

what type of valve would I need to get to try? Thanks

 

Try a Non thermostatic valve to see if it heats before spending more on a TRV.
If it don't work without one it certainly wont with one . But if you must......Danfoss RA-G !!

 

says `Bi-Directional Valve Body` so its not the issue, they work on both sides just fine, take the TRV heads off and it should be at full flow, just to rule out some bad batch of TRVs

are you able to check the pipe running under each radiator to see if they are warm though the whole run?

 

The pipe running under the radiators are both one. And the return pipe to the boiler is just as hot as the outbound flow! The radiator in the picture had the pipe adjusted and has 3 elbows forties might the cause the problem? I did take the rad off and ran a single pipe from flow to return and it got piping hot on both ends! I’ve seen some forums saying on a single pipe system they need full bore valves but I can’t find anything online

 

He has already confirmed it is a one pipe. Normal TRV's are too restrictive for gravity circulation due to the orifice size.