Draining Rad system with expansion vessel questions

9 Aug 2008
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United Kingdom
I was after abit of advice,

I have decided to put an extra radiator in downstairs as the room currently does not have one.
I am going to connect it via T joints from the radiator on the other side of the wall for flow and return.

On going upstairs to the bathroom cupboard to have a look properly (only been in the house a few months) I have noticed that I have an expansion vessel that is mounted right next to my hot water cylinder and the cold water storage tank is directly above the hot water cylinder. There is a gatevalve on the cold mains coming up to the cold water tank and then it is T'd off for a cold supply to the expansion vessel (which has a dial on it reading 2.5 bar and another needle set to 3 bar in red on same gauge) There is a filling loop connected to the expansion vessel, one end is connceted to the cold feed pipe which is positioned on and the expansion vessel end is positioned off. (isolating valve with lever type)
Do I need to turn off the cold water mains when draining my system and do I have to do anything to the expansion vessel at all? When draining the system?
And when re filling the system do I use the filling loop from the rising main to expansion vessel (like you would do on a combi system).

I have drained and refilled combi system and F+E tank systems in previous houses But have never come across a expansion vessel type one.

My second question is this... I dont have any TRV valves at all on any of the rads. The ones currently on are similar looking to the locksheild valves. Can I just put some on? There is a motorised valve, sorry if this sounds abit dumb and Im pretty sure I can, but just want to make sure.

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its no different to draining a combi, except the expansion vessel is an add on instead of being integral to the boiler, no problem adding TRVs but dont put one in room where room stat is fitted. When refilling 1bar should be enough.

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