Is it OK to do this on a Combi?

I've removed radiators (just as you are considering doing) and some have been out for a year during a renovation, no problems with the combi.

 

You usually get a screw-down cap along with TRV packs, so if you remove the TRV head you can screw this cap down instead to ensure the valve stays shut off.

You should be ok just closing off the TRV head all the way down to 'frost'. And provided you don't actually experience a frost, it should stay shut...

(Have plenty of low collecting dishes under these valves when you unscrew them and drain the rad, along with lots of towels/rags. The water that comes out could easily have black sludge in it, and you won't believe the inky mess that can make... )

 

Hi Fathands,make sure you cap the TRV off properly if the temp drops they will let by,it will be fine if your there working you can keep an eye on it,but I wouldn't leave it over night with out caping it properly I've seen a few puddles.

 

Quick tip for you FH, leave the bracket screws in their holes when you plaster, saves a lot of hassle trying to re hang the radiator afterwards. You will need to top up the system on the filling link when you have the radiator on the wall again.

 

Another tip Fats;

I usually whip of the rads when decorating and find a 9" roller tray is good for draining down (possibly one at each end of the rad)
The trays fit under even a low mounted rad and slide up tight to the skirting so you can catch all of the water - and that black sludge

Those TRVs look similar to mine and as above, come with a plastic cap which the instructions call a "decorating cap" - makes sense

I've had a couple of rad valves that haven't shut down completely and let the odd drip pass so have a couple of these in my decorating tools - gives a bit more piece of mind, especially overnight-http://www.screwfix.com/p/compressi...=Search-_-SearchRec-_-Area1&_requestid=276560

 

I use the 9" roller trays as well they work great.

 

Wet and dry hoover, but thats not an expense for a DIY'er never spill a drop

 

No worries fathands your welcome.

 

I've found some of those honeywell radplan trv's Let by a little bit when shut off and disconnected like you are intending. I usually use a compression nut olive and a little bit of 15mm pipe along with a push on stop end just to be on the safe side. has to be better than a puddle and a loss of system pressure.
I've got a triangular bowl that clips around the pipe for draining rads, I bought it at the local plumbers merchants.

 

All you need is a half inch blanking cap