Removing radiators from Combi system

[MarvinMartian]

I'm looking for a little advice regarding removing some radiators for decorating. I have some patches of plaster coming away from the wall behind several rads that I want to repair. The heating system runs off a Vaillant combi boiler (don't have model no to hand at the mo).

I've looked up some general info on radiator removal which suggests its just a case of closing the valves at each end, then draining the radiator. I did a test at the weekend and whilst this seemed to work, I also lost all pressure in the boiler system so I had no hot tap water, so had to put it all back together again before the plaster repair was dry (and hence unpainted)

What I'd like to be able to do is tackle each radiator in turn, but still have the tap water side working throughout, but I'm not sure if this is even possible now?

Is there some way to completely isolate the central heating side safely for a number of weeks?

Also on a related issue, the rads all have thermostatic valves - I read these can open when cold even if "shut off" and should be sealed. I picked up a couple of capnuts from Wickes, one 15mm and one 22mm but once I'd got the radiator off, found neither of these fitted the valve. Are there other fitting sizes? My flat is about 20 years old - is it possible they could still be imperial fittings?

Many thanks in advance
Ant

 

[Red_Man]

Buy some decorator caps from plumbers merchants.

Unscrew top part of TRV

Fit cap.

Isolate radiator at other end

Drain radiator. (make sure bleed is open during this.

Remove radiator

Check pressure.

If low (shouldn't be) repressurize boiler and keep an eye on where you have removed the rad.

 

[MarvinMartian]

Thanks for the reply Red_Man - when you say unscrew the top part of the TRV, do you mean the collar at its base (looks a bit like a hose clip with a screw through it) or should the bit that you normally twist to set the temp come apart from the rest of the valve?

Cheers
Ant

 

[Whitespirit66]

Yes, loosen the screw and carefully pull the head of the valve upwards to remove.

 

[MarvinMartian]

Cheers

 

[MIGEM]

Be careful doing this, and dont leave like this for a long period of time, and for no more than it takes for the paint to dry.
Fill your system, if not already, pressurise the boiler, shut off the flow and return valves under the boiler, drain the system and the boiler should remain pressurised. You will still have hot water.