Radiator not heating up...yes again!

[Trent800tech]

Firstly my apologies for bringing up what is an already well debated problem. However I am stuck and the symptoms are a little unusual....

The system is open vented. All other radiators get hot within minutes of boiler firing up so I think the system is relatively healthy.

The rad in question has been bugging us so we called British Gas under our CH cover plan. They advised me that we needed a powerflush and quoted £620.

I decided that I would attempt to recover that radiator by introducing Fernox F3 (after a drain down) and circulating for a week. This worked wonders on the lazy rad and it was incredibly hot with the rest.

However the F3 had to come out so I reluctantly drained it down and refilled without additives initially. Problem is now that rad is not getting hot again. I have now drained the system several times to no avail.

Thinking it may be obstructed again I introduced Sentinel X800 and tried to attack that rad by shutting all the rest off. The feed pipe gets hot and the inlet to the rad is hot. The outflow and return is cold. I took the TRV off and checked the pin for movement which there is. I tried manipulating the lock shield valve and draining off at the bleed valve but still it gets only tepid.

What could be the issue here? Would it be a good idea to fetch the rad off the wall and inspect it? Or is there anything else I could try? Is odd that it was working like a dream before I drained it to remove the F3. I understand that this may have brought an obstruction to the radiator again but where could that be? In the rad itself? It seemed to fill up OK on the refill.

Any advice appreciated..

 

[jeff the gasman]

Air in one of the legs. Turn off all other radiators and it should gurgle back into life.

 

[gigz]

+1. Failing that, take the rad off and flush it with a hosepipe. While its off flush the trv and lockshield into a dish (better still bit 15mm pipe with a 15mm nut connected to a hose and let it run) you should get about the same flow from both. If you have a blockage you need to clear it for the x800 to flow round.

 

[Trent800tech]

Thanks folks - sorry for the delay in replying though.

I have tried the first option there already and if left on for a few hours the rad gets tepid.

not yet taken the rad off so will be attempting that over the weekend. Thanks again.

 

[ianmcd]

make sure you have completely flushed the X800 out of your system or it might damage your pump if left in

 

[Trent800tech]

I did exactly as advised here and tried to chase out any airlock.

So today I drained down the system again in order to remove the x800 and attempt to recover that radiator.

Whilst drained down I took the rad off and blasted it through with a hose outside until there was no black water coming out of it (I made a thorough job of this turning and up-ending the rad as I went. I did the same with another rad too). I didn't connect up a hose to the flow and return to check throughput as I didn't have the parts to connect it up.

I also removed the TRV on faulty rad and checked for any obvious signs of blockage - none visible - and rinsed it under the tap.

Reconnected and refilled the system but still the rad is not performing so I am as confused as ever. The refill on that rad was pretty quick so I cannot imagine there is a blockage in the flow pipe.

I am now hitting that rad with the pump on and all other rads off. The flow is getting slightly warm but nothing to write home about.

Given that I have done all the above where should I turn next?

Cheers....

 

[Terry lambert]

If it has a I/2 inch blank on the top.

Shut the rad valves

Take out the blank

Put in a 1/2 male iron to compression with a bit of copper.

Attach hose andrun to bucket or drain

Open return and see what flow you get or if it clears the blockage

Shut return

Then same with flow