One cold radiatior...

[RoryJ1978]

So I have a 2 bed house, with gas central heating. Upstairs are 2 bedroom and 1 bathroom radiators (on 15mm pipe), downstairs 1 big lounge rad and one small one in hallway, both on 10mm pipe (no idea why they are different).

Anyway, the 2nd bedroom upstairs radiator never heats up, at all. Both valves turned full on.

I have been round all radiators and bled them, then round all again.
So, maybe its full of sludge? I have turned off both valves, removed radiator, flushed through in the bathtub - not blocked. Put back on, refills and all bled - still nothing.

Maybe its the feed to the radiator? Checked downstairs, the big one in the lounge (also lowest) is a big cooler in one corner - maybe sludge there? Drained whole system, took off and flushed it through with hose in the garden - not blocked but happy that i've flushed it anyway. Reattached (with new 10mm valve as that broke when turning it off), refilled system with tub of new inhibitor too.

Still no heat to the bedroom radiator.

Thinking about it overnight... I have tested that the bedroom rad's valves will shut off (as I could take that rad out without a flood), but I haven't actually tested that those valves will both open...

so apart from changing those valves - next weekend
Is there anything else I should be thinking about doing??

 

[terryplumb]

Is one valve a thermostatic on the cold rad ? May be pin is jammed closed ?

 

[RoryJ1978]

Pin seems go to in & out -- well will be replacing both valves anyway.

 

[jackthom]

Is the pin hard to push in against the spring and does it spring back out readily?

 

[terryplumb]

You could turn both valves off ,drain rad and remove. Connect hose to valve open valve and establish if water is flowing free thru valve ,test both valves.if they both allow flow no point changing as problem is elsewhere ,maybe just a balancing issue. Do you have a combi boiler ,or is it a gravity fed system boiler ?

 

[RoryJ1978]

Its a gravity fed system, boiler is downstairs in the kitchen. Connecting valves via a hose is a new idea, however just as easy to just open one with a towel over it and i'll soon see if its not working?

What's a balancing issue? This hasn't come up in my reading, what needs balancing and where??

 

[RoryJ1978]

Found a good diagram here--
www.kermi.com/en_com/thermal-comfort/hydraulic-balancing/

well thats worth a try too before the weekend - i would guess i have an upstairs 15mm circuit, and a separate 10mm downstairs circuit.
And the offending radiator is the furthest from the boiler...

 

[terryplumb]

Better with a hose directed to a bucket ,you can see the flow better ,and you need to do both valves. Balancing the CH is to ensure each rad is getting its fair share of hot water from the boiler.

 

[JohnD]

turn off all the hot ones. Does the cold one now heat up? If so, you do not have a blockage, but probably a balancing error.

Balancing means you restrict the flow on the radiators, so it doesn't all take the easy path, but is forced to go through all the rads. You do it by adjusting the lockshield valves, not the ones with a knob that you use for turning them on and off.

Correct setting will be in the region of fully closed, then about half a turn open. You may be surprised that it is so little.

 

[RoryJ1978]

Well I tried the radiator balancing, no joy (but interesting - had not thought about this before).

This morning have just completed hot swap of both valves (very little water spilt - good fun) - problem was definitely the thermostatic one not opening fully - and now all rads hot again.

THANK YOU all for your help!