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Discuss Combi boiler: water pressure question. in the Central Heating Forum area at UKPlumbersForums.co.uk.

  1. Max Tout

    Max Tout New Member

    My son recently moved house;...the CH boiler is an Ideal Logic Combi ES30 and it’s about 2 or 3 years old.

    When the system is cold the water pressure shows approx 1.9 bar,...when the CH has been on for a while and everything is fully heated-up the pressure gauge rises to approx 2.9 bar.

    If the boiler is then turned off the pressure returns to 1.9 bar within 15 mins or so.

    Is this pressure range normal?...is 2.9 bar too high?

    The CH and hot-water appears to be functioning perfectly.

    As ever, all advice gratefully received.
  2. Craig Watson

    Craig Watson Plumber GSR

    When your heating is on, pressure rise is Normal, but your sons pressure is set to high to start with, it should be set to 1bar when boiler is cold. Go round and bleed the radiators and make sure they're all full. If they are then attach a hose to the drain off valve and drain a little water out the system until it's around the 1 bar mark, but only do this when the heating is off and cold.
    • Agree Agree x 6
  3. Max Tout

    Max Tout New Member

    Many thanks for the reply Craig,...greatly appreciated.:)

    I’ve read a suggestion that it might be an expansion vessel pressure problem.

    However, there are no error codes of any kind on the display and everything appears to be functioning normally.

    I will reduce the water pressure as you suggest but in the meantime is 2.9 bar dangerous?...the water pressure gauge doesn’t show any ‘RED’ warning sectors.
  4. scott_d

    scott_d Plumber GSR Top Contributor!!

    Drop the pressure a bit now
    Get a full service. Not just a 15 minute check over
    • Agree Agree x 2
  5. Craig Watson

    Craig Watson Plumber GSR

    2.9 is just on the limit before the prv will open, not particularly dangerous but if the valve opens, it may not re-seat and will want replacing.
    Your expansion vessel is not at fault, pressure just set too high, that's all.

    And yeah, as Scott says, get a full service done.
    • Agree Agree x 2
  6. Max Tout

    Max Tout New Member

    Many thanks for the swift and helpful replies guys.:)

    Is a 1 bar fluctuation in pressure acceptable when going from cold to hot?;...or would you expect the difference to be less than 1 bar,...or maybe expect the pressure the remain stable?

    Does it vary from boiler to boiler manufacturer?
  7. rpm

    rpm Trusted Plumber Top Contributor!!

    Please see answers given above.
  8. Craig Watson

    Craig Watson Plumber GSR

    The pressure fluctuation varies depending on system size, when water heats up, it expands so the bigger the system, the bigger pressure increase. On a typical 10 rad system I would expect the pressure to increase from 1 bar to around 1.5 bar when heated. However because your system was already at a higher pressure, there is less room for expansion so when your system heats up, the pressure increase is greater.

    Drop the pressure, get the boiler serviced and it will be fine.
    • Agree Agree x 1
  9. Max Tout

    Max Tout New Member

    Thanks for the comprehensive reply Craig. Greatly appreciated.
  10. Max Tout

    Max Tout New Member

    Hi guys,

    As recommended, I reduced the water pressure to 1 bar in its cold state;...probably about 0.95 bar actually, but it’s difficult to be any more accurate given the vagaries of the gauge itself and the difficulty in actually reading it!..not the cleverest placement of an indicator gauge tbh.

    Checked all rads (10 rad system) for any air and and switched on. The CH temp selector was on its max setting.

    The water pressure climbed slowly and eventually settled at about 1.6 bar when fully heated-up and the burner had clicked off. When the burner was active the pressure climbed slightly to 1.7 bar but dropped back to 1.6 bar when the burner switched off.

    I’ll get a GSR engineer to give it a service this week but in the meantime any comments on the above info?..i.e. is it an indication of anything untoward etc?
  11. Craig Watson

    Craig Watson Plumber GSR

    By what you've said, everything sounds to be working normally, glad it's all sorted.
  12. Max Tout

    Max Tout New Member

    Many thanks Craig;...your expert opinion and guidance has been of great value.

    I’m presently trawling through the GSR list to book an engineer service visit,...it’s probably not had a service for a couple of years.
    • Like Like x 1
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