DIY Doctor

Worcester Combi - Dramatic pressure Increase when C/H on!

Postby HaveagoDIY » Tue Jan 08, 2008 9:45 am

Recently had a worcester bosch 28i installed and now when turn C/H on, pressure rises drastically from 1bar to ~3bar.

Also, when initially turn C/H on, can hear 'clicks' in pipes for about 1min.

Both seem to indicate air being trapped in system, but I have bled all radiators and each time, no air comes out.

Can there be an air block? Can air get 'sucked' into a combi boiler C/H system? Any ideas what could be wrong or how to fix?


Rank: Labourer
Progress to next rank:
Posts: 1
Joined: Tue Jan 08, 2008 9:06 am


Simply Build It

Postby htg engineer » Tue Jan 08, 2008 4:54 pm

If the pressure rises when the heating is on - this indicates a problem with the pressure vessel. It either needs re-pressurising or replacing.

The pressure will rise slightly when the heating or water is on. If the pressure is rising to 3bar with the heating on but it is not discharging to outside (overflowing) and returning back to 1.0bar when cool - it could just be the pressure vessel is too small for the size of the system.

If the boiler is under 12 months old - i'd get the manufacturers out and see what they say.

The clicking of pipes is normal as it is just expansion of the metal as there's hot water being pumped through it.
htg engineer
Rank: Project Manager
Posts: 3256
Joined: Tue May 22, 2007 5:22 pm

Display posts from previous
Sort by
Order by

  • DIY How to Project Guides
  • DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!

  • Related Topics