How to reduce comb boiler pressure??

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ks_lee13 | 21:43 Fri 22nd Dec 2006 | DIY
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Hi, my boiler gave up yesterday. I managed to fix the fan and now it works. however the pressure gauge is now 2-2.5bar. It use to be about 1bar. How can i reduce the pressure. Which valves do i open?? thanks


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It is normal to be around the figure you quoted if the heating is on and the radiators or hot !! Water expands when it is hot and so the pressure will rise . But if it is at 2 - 2.5 Bar when the system is cold then if you get a suitable container and place it on a few old towels under a rad, and open up the bleed nipple on a radiator as if you where bleeding it. But just let the water flow out till the pressure has fallen to approx 1 Bar. The correct pressuer When Cold and static is 1.0 Bar + 0.1 of a Bar for every additional meter of head.
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is there a way to relive pressure from the boiler instead of the radiators. Im looking at a CH flow , CH return **** to adjust, but dont know which one. I have a pipe comming outside of the house , presumably releasing pressure the water will flow out there

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by the way, does it matter which radiator i bleed out to reduce pressure? will the water redistribute itself amongst the 7 other radiators i have at home??
By doing as i have suggested the pressure in the boiler will fall as the whole system ie. the rads the boiler and all the pipework are as one and all at the same pressure. Best not to touch anything on the boiler especialy the saftey valve pipe as they have a tendancy to not shut down properly after they have been disturbed. And remember 1 Bar when COLD...
No it will not matter but as good practice we will always vent the highest rad in the system ( usualy the bathroom ).
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thanks gasman, I will try this as soon as the heating in the house has cooled down. But why did the pressure increase in the first place (how did extra water enter the system?)
Very good question, the filling loop may have been left in place and if it is faulty or has not been shut off all the way then it will allow the water to get into the system. The filling loop should never be left connected it is only a temp device for filling up a system so remove it when you have finnished. If there a problem occours and it is in position you could end up polouting your drinking water..

Also if the expansion vessle has failed then this will also make the pressure go up as it is not compensating for the pressure rise. So if there is nothing wrong with the filling loop and it is diconnected. You could be looking at expansion vessle failure.

Then again you could just have a faulty pressure guage
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lastly, do i need to turn off the main water supply before proceeding to bleed the radiator

thanks for your help
No the water in the system is totaly independant from the mains water and therefore there is no need to do anything apart from what i have suggested.
Good luck. and a merry christmas to you.
Is it normal to hear the water running all the time in the boiler after pressurise it??

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