Cold Radiator

[fbg40]

Rather a long question but please bear with me. Back in May I asked about having my CH system power flushed - too expensive so decided against it. I have 2 rads in my lounge, one of which is always cold. I've had the valves changed, a new CH pump and a new motor fitted to the 3 way valve (It was giving up the ghost). Can anybody provide a possible cure for this cold rad ? As far as I'm concerned there must be a blockage somewhere, so would it help if I were to take the rad off and give it a good flush through ? I can only assume that if I did this and the rad was still cold there must be blockage in the pipework. Anyhelp/advice would be greatly appreciated. Many thanks.
FBG40

[bobbinwales]

Sorry if you already done all this.
Is it defintely turned on... you tried turning the valves on each side.
Have you bled the radiator.
Have you ballanced your radiators- tried turning down the ones before and after in the sequence

[fbg40]

B
Yes tried everything !! Thanks for replying.
FBG40

[Atheist]

When you bleed it, does water start to trickle out of the bleed valve?

[Togo]

Is the "inlet" or inflow pipework to the rad getting warm along any of it's length? I know that it may be under the floorboards or hidden behind boxwork. If it is warm it looks like a rad that is blocked. When you had the valves changed did you drain down? If you drained down did water (very dirty water) come from the inflow pipe? If it did you are back to the rad being blocked solid. Over time the iron rads deposit Fe₂O₃ into the sealed water circuit that settles in the low point or farthest point from the pump over the summer months. The particles can form a solid lump in the bottom of a rad which stops the flow entirely. When we had a new boiler fitted I had a magnetic filter fitted that collects all the fine iron particles and keeps the rads and the boiler free of the iron sludge.

[fbg40]

1) Atheist : yes, water does flow from the bleed valve.
2)Togo : The inlet is sometimes lukewarm, sometimes cold. When the valves were changed the plumber used rubber "bungs" in the header tank, opened the drain valve until no more water appeared. I do have a Magnatec Professional filter installed in the system. Many thanks for the answers folks.
FBG40

[Atheist]

fbg; Is there a thermostastic radiator valve on the radiator? If there is, it can sometimes stick in the off position. That can usually be resolved easily by removing the TRV head and pushing ior pulling the small metal pin which sticks up from the valve.

[fbg40]

Morning Atheist,
Yes there is a TRV on the rad - a brand new one !! Both valves were replaced. Thanks for asking.
FBG40

[The Builder]

Considering a possible bung-up fbg, do you have mini-bore or worse still micro-bore pipework?
(10mm, 8mm)

[fbg40]

Hi Builder,
No - it's normal 15mm.
FBG40

[davebro]

//do you have mini-bore or worse still micro-bore pipework?//

I have that - apart from one blocked rad about 30 years ago no problems whatsoever!

[The Builder]

Fair enough Dave. It was just a thought. If there's any sludge around, small-bore is susceptible.

Further to bobbin's post... I had just this problem in a previous house.
I went around the whole house and turned the TRVs down to nothing, except for the problematic one.
That effectively meant the pump was powering that one rad.
It came to life and started working perfectly.
One by one I turned each rad to "three". Everything was fine then.
(You can then turn each rad back to your desired setting.)

I can only assume it shifted an airlock.

[fbg40]

Thanks Builder, will give it a try.
FBG40