Purposly leaving air in CH system - rad in attic?

[JoeA]

The previous owners thought it would be a good idea to put a radiator in the attic of our house, which we have now insulated meaning the attic will get much colder in the winter.

I always keep both valves on this radiator turned off so as not to waste heat in the attic! So this means the water in most of the length of the feed and return pipes is never heated - the radiator is right at the end of a spur in the CH system.

Because of this I have been worrying about the pipes freezing in winter. Then I had the idea of draining the whole CH system, and then keeping all the valves to the attic radiator closed when I re filled the system - presumably leaving a big air lock right at the top of the system, and meaning most of the length of the feed and return pipes to the attic rad will be empty of water. Is this a good or a bad idea?

Is it possible that some of the air will find its way into the rest of the system? Logic says it shouldn't as the attic and the pipes to the attic rad are the highest point in the system...is there anything else I haven't thought of that could cause a problem with this idea?

Cheers.

 

[avonmouth]

Drain system and put two isolation valves on the pipes where they T off or cut them off completely using stop ends.
Your way won't work.

 

[JoeA]

I knew it couldn't be that easy! I was hoping to avoid more work. I think I'll just fill the system as normal and get some pipe insulation for the exposed bits of pipe in the attic.

Cheers.

 

[mogget]

Pipe insulation will not stop freezing in and of itself. Unless at least some water flows from time to time, the pipe will eventually drop to the surrounding temperature. If this radiator has no purpose it would be better to remove it properly. Air will eventually dissolve into the water and pop up somewhere else.

But I wonder why there is a radiator in a presumably unconverted attic. Possibly there was a condensation problem, for which the proper solution is to draught proof the attic hatch and ensure adequate roof space ventilation.

Avonmouth's solution is the correct one re the heating.

 

[ScottishGasMan]

Yup, the air eventually dissolves into the water and then contributes to system corrosion, as well as the inside of the radiator rusting away.

If its not going to get used then cap the pipes and remove it. If it is then insulate the pipes and use a Thermostatic rad valve to ensure warm water flows throught it when its cold enough, but as already said, youd be better getting rid of.