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- 7 Apr 2007
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Hi - Made the fatal mistake of bleeding air out of a couple of radiators and now my sealed cental heating system fails to start every morning. Brrr.
I have refilled the system to just over 1 bar, and it works fine all day, but by the next morning the pressure has dropped to 0.8 bar and the boiler locks out. No obvious leaks anywhere.
What I *think* is happening:
The system volume is quite large (old victorian house with 4 floors and approx 25 rads). When it gets hot the pressure gets up to nearly 3 bar and tapping the pressure relief valve causes a pressure dump. I think this is happening during the day, then overnight when the system cools the pressure drops below 1 bar and the boiler locks out.
Before I drained the radiators of air, the pressures went from about 1 bar cold to about 1.5 hot. Haven't needed to top up the system for quite a while.
It could be due to a leak only revealed by the higher pressures in the system recently... but I have no sign of it.
I figured the radiators full of air were probably working as an expansion vessel, helping to limit the pressure rise in the system. After I bled them, no air to compress therefore higher pressures and pressure relief valve dumping. So... should I just fit an extra expansion vessel (8L or so). The boiler's expansion vessel is 7L.
If I do fit another expansion vessel, does it need a filling loop if it is not the primary method of filling the system? How do you get the new vessel to fill with water from the system initially? Is there a bleed valve or something?
I am quite up to the job of fitting a new vessel, but have never had to use one before.
Regards,
Oz
I have refilled the system to just over 1 bar, and it works fine all day, but by the next morning the pressure has dropped to 0.8 bar and the boiler locks out. No obvious leaks anywhere.
What I *think* is happening:
The system volume is quite large (old victorian house with 4 floors and approx 25 rads). When it gets hot the pressure gets up to nearly 3 bar and tapping the pressure relief valve causes a pressure dump. I think this is happening during the day, then overnight when the system cools the pressure drops below 1 bar and the boiler locks out.
Before I drained the radiators of air, the pressures went from about 1 bar cold to about 1.5 hot. Haven't needed to top up the system for quite a while.
It could be due to a leak only revealed by the higher pressures in the system recently... but I have no sign of it.
I figured the radiators full of air were probably working as an expansion vessel, helping to limit the pressure rise in the system. After I bled them, no air to compress therefore higher pressures and pressure relief valve dumping. So... should I just fit an extra expansion vessel (8L or so). The boiler's expansion vessel is 7L.
If I do fit another expansion vessel, does it need a filling loop if it is not the primary method of filling the system? How do you get the new vessel to fill with water from the system initially? Is there a bleed valve or something?
I am quite up to the job of fitting a new vessel, but have never had to use one before.
Regards,
Oz