Combi boiler Q

[John Rumm]

Have you established if its losing water from the PRV yet? (use the bag tied over the outlet trick to find out)

[rick]

Established it was 'all right by dropping water pressure ... and checking the vessel pressure .. first no water on the air side (so diaphragm not ruptured) secondly it was charged to 0.95bar and thus no leak on air side.

Current thought is it could be the PRV ... so ordered one to fit

[Andrew Gabriel]

If you leave it permanently open, it will eventually leak. It relies on a water seal to keep it closed. This will dry from the air-side leaving a tiny amount of scale. This happens each time it operates and eventually the scale will build up enough to stop it from sealing.

Typically, leave it open for a day after refilling following a drain-down, and then momentarily open it periodically after that. Another good time is during or shortly after running at highest flow temperature you use (typically when winter gets cold if you vary the flow temp to compensate for outdoor temperatures), as that heat liberates additional dissolved gasses from the water.

[rick]

Yes it is ... and new PRV ordered - will pick it up tomorrow

[rick]

Boiler installation manual states to set to 1/2 turn open and leave it that way.

[Tim+]

I think you're ignoring good advice. Our boiler PCBs were ruined by water leaking down from an automatic air vent situated above our boiler.

Of course your bleed valve may be better sited but I think Andrew advice is sound.

Tim

[John Rumm]

You can sometimes resurrect old ones, by giving them a good de-scale in fernox DS3 or similar.

I had one that was letting by slowly on my unvented cylinder. Turned out to be a bit of scale. De-scaling helped, but did not quite fix it since the scale had pitted the sealing face very slightly. I needed to re-dress the edge with a bit of emery cloth, and that fixed it.

[John Rumm]

Yup, I would agree - once the boiler is vented during installation, there is no real need for it. Any extra gas will find its way to a rad where it can be bled easily enough.

[Roger Hayter]

Unimpressive shower but comparable with an electric one, even allowing for lower efficiency.

[Dave Plowman (News)]

It's more like what you'd expect to pay to have a new (cheap) boiler fitted to an existing system.