Bleeding radiators with a Greenstar boiler

Our radiators needed bleeding to remove excess air (they were hot at the bottom, and cooler towards the top). But we need to get more water into the system via our Greenstar 24i junior (or 28i junior) boiler, as the panel was showing a pressure of around 0.5. Here’s how.

We had the installation instruction manual, which explained how to first fill the system, but had too much detail. We also have the User Instruction Guide which mentions nothing.

  • On the bottom cover of the boiler is a plastic tray with a recess that holds a white plastic tubular key. The tray comes off.
  • You’ll also see underneath the boiler, a plastic white square nut, next to a tubular hole.
  • Push the plastic key into the tubular hole. It should go up 3-4 centimeters. Twist it clockwise slowly, and when correctly aligned, it should go in another centimeter. Keep twisting about a quarter of a turn, until is stops. If you look careful on the outside of the tube, there is embossed a padlock symbol indicating the position when the key is in the open position
  • Now you can turn the white square plastic nut, anticlockwise with your fingers. You’ll hear water start to flow, and the pressure gauge will start to increase. The ideal pressure is about 1.5 bar (anywhere between 1-3 is in green). If you can’t move it with your fingers, a wide flat-blade screwdriver will help.
  • Update 19 Jan 2012: Thanks to Richard for noting that after turning the white square plastic nut back (clockwise) and hearing the water stop flowing, the key comes out when it, and the padlock symbol, is in the open position, which seems counter-intuitive!

With pressure in the system, you’ll be able to bleed your radiators. As you bleed them, the water pressure will drop, and you may need to refill them.

Details can be checked with the manufacturer’s, Worcester Bosch, Tel: 01905 754624. See also the Greenstar 24i/28i junior brochure.