hi

i have a Worcester Bosch 24i RSF boiler and pressure bar is about 3-3.5 bars now. it usually was about 1-1.5. yesterday we had some problems with the tap, so i turn the mains off to fix it. after we turn the mains on, the pressure went high to 2-2.5. after couple of hours later it is 3-3.5 now. we still have hot water and heating with no problems, but i dont know why the pressure is so high. when i turn the mains off - it goes down.

Thomas, November 2009

hi its unlikely that the HW is leaking into the CH , this would require two damaged pipes and a leap across a gap. ,so unless someone has recently been altering your pipe work ,its more likley to be the filling loop , this is something close to the boiler , probably a braded hose with an inline tap , which should be off. it should also have a nut to disconnect it comletly, but if you take it off to check, do it with the mains water off, only other thing is could you be confusing the natural increas in preasure that happens when the CH goes up in temprature , usualy to a max 3 bar.

warren, November 2009

As before - there isn't (or shouldn't be) any connection between the DHW and the central heating - its only the CH that uses the pressure gauge. So, water must be passing from the DHW into the CH side - due to a heat exchanger fault. Not recommended! I think I'd be giving the boiler repair men a call, really.

John, November 2009

when i turn the mains on - the pressure rises. the washing machine is on now, so the pressure went down to about 1.5-2 bars now. so, what do you suggest now ? thx

Thomas, November 2009

OK so when you turn the house mains on, the pressure in the boiler rises, right? So, this points to the filling loop not fully off, or this leak between the heat exchangers that I'm going on about. It sounds like the latter, unfortunately, as you say that the pressure falls again with the mains water off.

John, November 2009

it was nothing really, i was installing new hot water knob in the kitchen sink tap, so thats why i turned the mains off

Thomas, November 2009

Combi boilers have a sealed central heating system which is filled with water via a special tap called a filling loop. Once the water is in there it is left alone - unless the system is disturbed in some way. There is no connection between the central heating circuit and domestic hot water which you use at the taps. Therefore, turning the house mains water off and on should have no effect on the boiler pressure. However, as the pressure is increasing and you haven't disturbed the filling loop, it does look like the domestic hot water heat exchanger is leaking into the central heating heat exchanger, unfortunately. The pressure release valve should lift at 3 bar and allow water to escape outside. You mention having had problems with 'the tap'.....which tap?

John, November 2009

filling loop ? sorry but im a complete noob in these things...the thing is - i didnt mess around with the boiler at all. the tap thing wasnt boiler related. i was just installing new tap, so ive turn the mains off and after that turn it back on and pressure risen. it also makes souns like its releasing air or water or something. can you tell me where can i locate that filling loop thing ?

Thomas, November 2009

The filling loop tap is still letting water pass...check thats its fully off, and disconnected if possible.

John, November 2009