Cold patch on new radiator

[Markham]

Hi
I need some help and don't know what to try next.
I've fitted a new compact double pannel rad. It has a TRV( direction dependant but fitted in right direction of flow) on the exit pipe and standard lockshield on the inbound.
With the heating on, even when all other rads are turned off only the top and less so the sides get hot. The inbound valve gets hot. Out bound stays cold. Pipe work is 10mm plastic 14yrs old.
I can drain water back thru both valves if opened when disconnected. I know its not sludge in rad and removing the TRV makes no difference...can anybody please advise. Many thanks

 

[Timmyturtle]

Double check the trv flow is right way round

could be air stuck in pipe somewhere if its been drained?

Something in the rad that shouldnt be (possibly from factory)

How big is the rad?

 

[Markham]

Thanks for getting back. Really apprecite it.
The rad is 700x1000.
Its a repalcement radiator and I had the same probs with the original but thought it was rusted up.
The TRV has gone back the same way. When it came to filling the rad I opened the TRV(on the exit pipe) and it filled. Should this not happen if its a unidirectional valve.
Thanks again

 

[Nige F]

Thanks for getting back. Really apprecite it.
and I had the same probs with the original but .....Thanks again

10mm pipe won`t help, either

 

[Agile]

It sounds as if it may just be a balancing problem.

Does it get hot if you turn all the others off?

Tony

 

[Markham]

I've tried shutting all the other rads down and just leaving the problem one open but with no real improvement.
I know it used to work as the radiator did work briefly when we first moved in.
Thanks for all the advice. Keep it comimg. I'll try anything.......well almost.

 

[JohnD]

sludge in the pipe.

http://www.diynot.com/search/forum....t=3&author=&search=Search+Forum&mode=advanced

 

[Markham]

Thanks again all. I'm starting to think that JohnD is right and sludge is the only poss cause in the feed/exit pipes. Its a closed system and I would consider a power flush after a couple of weeks cleansing.
I cleaned the system chemically last year (no PF) with some improvement overall and water in system now runs clear but may not have shifted all of it.
Worth trying again? Is the powerflush going to help?

 

[JohnD]

I'm starting to think that JohnD is right

eek!


I know nothing about plastic pipe, but I believe that some of it was permeable and air can get in and cause corrosion.

Someone will know how to identify it.

When you bleed the rad, what colour is the water?

Have you got any copper pipe in the system?

 

[Markham]

Thanks John. There are the usual main feed/return pipes around the boiler and tank that are copper in standard sizes. I've fitted a boiler buddy since the cleanse that traps some black stuff.
Water is clear on draining rad.

I susp that some of the plastic pipe is gas permeable. The system does loose water from somewhere but I can't find any leaks anywhere.
One of the diverter swithches my not be working well either as some rads get hot even when CH off but HW on.

 

[JohnD]

glad to hear you have a Buddy on it. If you slosh in some X400 it will loosen any black sediment from the pipes and you should be able to see it in the Buddy. That will give you an indication of the size of any sludge problem. You can leave it in for weeks if you want, but you need an inhibitor to prevent future corrosion.

 

[Markham]

Shows my joined up thinking. Having been convinced it was the rad I've just topped up with Inhibitor. Do I need to drain completely with the X400 or can I add it to the system with ihnhibitor in it?
Thanks. Markham

 

[croydoncorgi]

If the problem only affects one rad, you might try a 'cheap flush'. Even if it doesn't do any real good, it should give some indication of where the problem is and how bad. (It'll work best if you have a pressurised, sealed system, OK if you're on the ground floor with an F&E tank in the loft and probably a waste of time with a 'low-level' F&E in an apartment or bungalow).

Turn off the boiler and heating. Close the rads valves at BOTH ends of the affected rad. If it's a TRV, ideally use the 'isolating knob' that replaces the TRV head. Slacken the nut on the 'tail' between the valve and the rad and drain the rad contents using a paint tray or whatever. Carefully undo both tails and remove the rad, avoiding black sludge on the white Axminster. Make up a fitting that will attach to the valve and convert to 'hose-size' (15mm copper). Fit a hose onto the valve WITH a jubilee clip. and open the valve with the end of a hose in a bucket (preferably outside). See what (if anything) comes out with the water. With only 10mm pipes, you should get a good flow-rate even relying on just the pressure in a sealed system expansion vessel. Re-pressurise the system and repeat on the other valve. If you get lots of black crud (or, worse, Brown Windsor soup) you'll need to circulate some heavy duty cleaner for up to a week, then do some major flushing.