Draining the CH system

4 Feb 2006
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United Kingdom

I have installed one radiator and moved another. Now I am ready to connect up to the CH system. I have found the drain valve no problem so I went in to the loft to the expansion tank to secure the ball valve so the system did not fill up while I was emptying the water.
This is where I get confused. There are 3 pipes to the expansion tank, a cold top up, cold feed to the hot water tank and the overflow and that's it. There is no feed for the CH system although there is an expansion pipe that goes up to the expansion tank.

Where does the feed to the CH come from. I don't think it is a sealed system as there is an expansion pipe. Do I refill the system through the drain point? Also is it safe adding rust inhibiter to the system as there is potential for this to expand in to the tank that feeds the hot water supply?

God I'm confused....
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cold feed to the hot water tank
That is probably the 15mm feed and expansion pipe for the heating system. It joins the CH system pipework near the cylinder, but is not the cylinder feed, which will be a 22mm pipe to the very bottom of the cylinder. Locate this and follow it back up for the hot water cold feed tank.

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