how to refill central heating system?

Thanks alot for that answer!

Matt
August 2007

It depends on whether you have an open vented or sealed system. Its more than likely open vented if you have a suprima. The way to check is to have a look in your loft. You should have a 2 tanks up there if your system is open vented, 1 for cold water which is quite big, and another to fill your heating, which is alot smaller than the cold storage tank. If you have this system then here's what you do. Either tie up the ball valve on the small tank to stop it from automatically filling when you start to drain the heating, or, and this way is alot easier, just turn off your mains water stop cock. Then drain the heating system. When you want to refill, simply turn the mains back on and vent your rads. A couple of important points to note though, check to see if there is a vent in your airing cupboard when you go to refill, if there is then vent it, make sure you cut the power to the system BEFORE you drain it as it will f**k your system if it fires with no water in it, when you go to refill, before you turn the mains water back on, open the cold tap on the kitchen sink and leave open untill the mains is back on. The reason for this is if you have any debri in the mains pipe it will come out the tap instead of shooting up to the ball valve on the tank and blocking the restricter.
If you find that you don't have 2 tanks in the loft then look for a round red expansion vessel, there is usually a pressure gauge near to it and more often than not, it will be found in the airing cupboard. If you have that type pf system then you don't need to turn anything off to drain, just drain the system. When you need to refill however, you will need to find the filling loop, this is probably near to the expansion vessel and is usually silver, flexible pipe with a a valve on 1 or both ends. The valve will either have a black handle on it or a flat screwdriver slot. Either way these are called quarter turn valves. Turn the handle or slot till you can hear water passing through it, only fill the system to 1 BAR, this is very important, bleed the rads, if air stops coming out while bleeding then put more pressure in, but make sure when your finnished bleeding that you have 1 Bar of pressure in the system, the pressure gauge is usually near the filling loop. THE END.

Neil (Baxi engineer)
August 2007