Fitting a thermostatic valve to a rad on a combi system?

[Redditchmick]

The smallest bedroom in our house gets too hot if the radiator's on, so that our son falls asleep instead of doing his college work!

We have a combi system with a Potterton Combi 80 in the garage. How can I fit a thermostatic valve to this bedroom radiator in place of the existing one?

Won't water come pouring out when I unscrew it, or will shutting off the lockshield at the other end be enough, providing the heating's off and I catch the water draining out of the rad itself?

There's clearly no header tank, so the 'bung' method's a non-starter.

Any help much appreciated.

Regards,
Mick

 

[gas4you]

Turn the boiler off and via a drain cock under a radiator or the boiler drain the system down, opening the air bleed valves on each upstairs rad.

When water stops coming out of drain you should be able to remove the old valve and fit the new one.

Don't forget to add new inhibitor before refilling the system.

 

[Redditchmick]

OK thanks, gas4u.

There are two valves under the boiler, 1 with a black plastic 'flag' handle, the other with a red iron wheel. My guess is the black one's the feed and the red iron one's the drain, so I'd turn off both, disconnect the linking pipe from the black one and connect it to a hose leading to the house drain, open the rad bleeds and then turn on the red one.

How/where do I add the rust inhibitor?

Sorry to be a pain.

Regards,
Mick