Pressure too high on gauge of combi boiler

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mwrmusic | 14:04 Tue 17th May 2005 | Home & Garden
11 Answers
I recently noticed that the pressure on the boiler was 0.6 bar. I opened the top-up valve but the gauge suddenly jumped to 2.5 bar! When the boiler is in operation, the needle on the gauge keeps rising past 3 bar until I stop it. How can I release the pressure? The boiler is a Powermax 155x. Please help...


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Please don't quote me on this but my dad is a plumber and I had problems with my boiler as couple of months back and I remember my dad talking about the pressure gauge and what to do. I think you need to release the pressure by using a filling loop which is a little tap and it will be found somewhere on your boiler.  It releases pressure and water.  Sorry I haven't been helpful, I hope you get some posts on here which are.
You can release pressure by simply bleeding a rad. If you do not have one buy a key from a diy shop and the bleed a rad until you reach the desired pressure
Normally if the pressure has got too high the overflow on the boiler will automatically go to relieve some of the pressure by itself.

You opened the top up valve too quickly and let too much mains pressure water into the closed system.  Your mains water pressure must be 2.5 bar or more. As above reply, the best way is to let a little water out of one of the rads to reduce the pressure again.  It is unlikely to do any immediate harm, but you should do it because the system is designed to work at 2.5 bar and you are stressing the internal components.

The reply above that suggests leaving it alone is ill-informed.  It is true that combis have a pressure-relieving circuit. Depending on the system design it is usually set around the 6 bar mark.  But this is designed the stop the thing blowing up under fault conditions - it doesn't mean that it is alright.

Sorry - there is a missing NOT in the last sentence of the 1st para - the system is not designed to operate at 2.5 bar.
ah hem! normal working pressure= 1.5 bar, with an automatic water discharge at 3 bar! sometimes the pressure will top 3 bar without this happening but thats just because the  valve will be stuck!
i am a heating engineer if you set pressure to 1 bar (when cold) then apply heat to appliance & pressure goes above 2.5 bar you will need expansion vessel re-pressurising by corgi only engineer
wait a minute!you are all wrong.when your system is running check to see were temp is at its highest point and then check your pressure!it should reach its highest temp then you can remove some pressure,but it should be done BY a licenced oiler boiler mechanic!you can really hurt your self or someone esle!
I have a Ferroli combi boiler. The pressure gauge is quite high. I've bled the radiators and topped it up. However, when the heating is on, the pressure gauge is alarmingly high again. I then turn off the heating, but overnight, the gauge goes right below normal by which time I repeat the process of topping up etc. Any advice please? Thank you.
I had the same problem with my Ariston Combi boiler about 3 yrs ago, It seems to be doing the same thing again. 1st you notice when you use the hot water sometimes the boiler shuts down espectially if your bath room is farther way from your boiler. In my case the boiler is down stairs in the litchen and bathroom is upstairs. It does not shut down if I use the kitchen tap.

1. Switch off the power ro Boiler
2. Drain some of the water till the guage registers "0" on the boiler guage
3. At the back of the boiler where the flue comes out, there a metal ballaon ball behind the boiler with a bike pump screew
4. unscrew the cap, place a biycele pump, pump it till the pressure is 1 mm bar
5. Measure the pressure where you place the pump.
6. Do the pressure and measure the pressure at intervals etc
7. Replace the cap and refill the boiler and switch the power on.
8. please note, do not use motorised pump. it will also be better if you buy a pressure meter guage which registers not more than 5 bar (Halford or carprts shops).

Good luck, as am going to do my agian today
You have to go outside to your drain for the central heating and let some water out until the pressure drops to about 1-1.5bar.This will be a sealed system and there is too much water in the system.
Do it gradually getting someone to check pressure at boiler when you are letting water out.
At 3 bar the safety pressure release valve is ready to operate to vent water outside.
If you have it at 1.5bar when operating it may rise to 2 bar max.
If it keeps rising after draining water out you may have a faulty diaphram in your expantion tank along water to bypass and repressure system

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Pressure too high on gauge of combi boiler

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