Unvented drain down

[bennettp23]

Hi,

I need to move a filter and do a little radiator work. I have an unvented system which also hjas a solar feed too - please see pictures.

I believe it is a 'S' plan set up? There are several taps installed which may help?

Now, when I drain down the radiators does that also drain down the unvented cylinder? I'm wondering about how much inhibitor will be required. Going to use Flomasta concentrated inhibited antifreeze. I have 16 rads. The cylinder is 210 litres so need to know if I have to take that into consideration? If not, I think 1.5 litres will work, if the cylinder does drain I will need more.

Also, I appear to have an F&E tank which is confusing as the system is unvented. Is this feeding the central heating side only which implies they are separate systems and I can then add the inhibitor to the F&E tank and the cylinder won't drain?

Thanks for any help!

Paul.

 

[ianmcd]

you seem to have an S plan open vent heating system with an unvented HW cylinder, not common but have seen some, you wont need to drain the cylinder to work on the heating system

 

[bennettp23]

Thanks Ian.

So:

1. Tie off the ball cock
2. Turn off heating at breaker/switch by boiler
3. Do I need to manually open the CH valve in the S config so it drains?
4. Will I need to use any of the taps to isolate the cylinder? I can follow the pipes so can identify what is what.
5. Will only be working upstairs so attach hose to downstairs drain point and raise end to downstairs ceiling height (does that work?)
6. Drain from downstairs drain point - opening bleed points on upstairs rads.
7. Do work
8. reverse above, add inhibitor before letting ball cock go.
9. Bleed rads.

Thanks so much!

 

[ianmcd]

Yes you have got it all correct , but rather than tie up the ball cock have a look and see if there is a stop valve on the inlet and close that , much more secure, looks like a decent installation so would expect one to be there , make sure there is not crud in the bottom of the F&E tank as this will be drawn into the system when draining, if there is clean it out before draining

 

[bennettp23]

Thanks Ian - can I just clarify points 3 and 4?

• Do I need to manually open the CH valve in the S config so it drains?

• Will I need to use any of the taps to isolate the cylinder? I can follow the pipes so can identify what is what if needed.