Draing down S plan central heating system

[Unregistered]

I have a standard vented S plan system and I'm about to increase the sixe of a couple of radiators. I'll also take the opportunity to refill with new inhibitor.

My question is whether I need to manually open both S plan valves when I drain the system. I see no reference to this in any guides I've read, but it seems to make sense to do this... or does it.
For reference, I only plan on draining down the feeds to the two rads that I plan to change. However, they are both ground floor and are fed from above (two separate feeds), so this will probably drain most of the system in any case.

I then plan to let the F&E fill while continuing to drain from the two new radiators in order to allow the system to be flushed.

Do I need to manually open the valves.

Thanks in advance for any advice.
T

 

[townfanjon]

Yes, but more so because it helps when you refill

 

[Unregistered]

Thought so. Many thanks for the quick response.

Terry

 

[Robert Tyrrell]

If you're flushing the system, put some system cleaner in and run it for a few hours before draining. This will help to loosen all the 'sludge' in the system, then flush with cold water to clear before filling and adding inhibitor.
It won't beat a power flush but something is better than nothing I suppose

 

[Dotty]

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