Removing a Rad on Combi Boiler system

Postby rich31 » Mon Jul 30, 2007 9:11 am

Am in the middle of decorating and would like to temporarily remove a large rad in order to be able to get to the skirting boards. I have recently moved into a house that has a combi boiler (a Worcester I believe). I've removed a rad before but never where it is hooked up to a cmbi boiler system. I've read something about this fact making it much more difficult and that I might get pressure problems with the boiler afterwards. I don't want to save money by doing the rad myself only to then have to pay a professional to come and fix any resulting problems with the boiler! Can anyone out there explain how I can go about doing this myself or, is it something that really should be left to an expert on this occasion? Many thanks in advance.
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Simply Build It

Postby htg engineer » Wed Aug 01, 2007 4:17 pm

Turn off both radiator valves and remove the radiator. The pressure on the boiler may drop, when removing the radiator, but will definately drop when replacing it.

The pressure is shown on a pressure gauge on the boiler, this should be between 1.0 and 1.5bar. If the pressure drops to 0 normally below 0.5 then the boiler wont work.

The system can be re-pressurised by the combi fill, Sometimes an internal fill loop or can be an external loop that has to be connected with a flexible hose.

Does your boiler have a white key with it ? if it does then its a internal combi fill and it will tell you in the boiler instructions how to re-pressurise.

If you can find out how to re-pressurise the system then the rest is easy. Refit radiator, open valves and vent until water comes out of bleed point. whilst keeping the pressure on about 1.0bar. When the system is full pressurise to about 1.5 bar and check for leaks. Job done.
htg engineer
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Postby rich31 » Thu Aug 02, 2007 4:36 pm

Thanks, that's great. Yes it has a white key with it which is next to a grey dial with I assume is the thing to turn to get the pressure back up. The pressure is showing as somewhere between 0.5 and 0.7 so quite low already. You make it sound very simple, but I am sure I will do my best to mess it up! Should I cap the valves when I undo the radiator or can I rely on turning them off fully (there is a thermostatic valve at one end). Cheers.
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Postby muzza » Thu Aug 02, 2007 7:12 pm

Just turn them off, cap them if they continue to drip

Be careful when refilling, the system pressure varies with temperature. If the other rads are hot the pressure will be above 1 bar, 1 bar is normally the cold fill pressure. Would suggest turning off the heating and letting all rads cool, not a problem in the summer when heating is swithced off but something to bear in mind if you do it in winter
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Postby htg engineer » Thu Aug 02, 2007 8:25 pm

some thermostatic radiator valves will not turn off fully with the thermostatic heads, do you have a plastic cap that would have been on the valve when it was bought ?

if so put this on in place of the thermostatic head and the valve will be closed, if not, you may need to drain the system or get a cap to fit the valve.

ps. be careful with the grey knob on the combi fill, they snap fairly easy, don't over tighten when closing, had a job yesterday where the tenant had snapped one.

hope this helps
htg engineer
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Joined: Tue May 22, 2007 5:22 pm

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