Update to Sealed CH System

[andy.hide]

I'm in the process of converting my open vented system to sealed in readiness for installation of new condensing boiler. Plan is to run flow/return pipework to new location and get Corgi fitter to fit boiler and run new gas pipe. HW cylinder, controls etc already replaced and updated to latest building regs.

Existing (ancient) backboiler is a Glow Worm 240/6 or 246. My question is whether I can run this unit as a sealed system in the interim after converting to sealed but before fitting new boiler ?

I can't find any manuals on the Glow Worm web site (far too old) but neighbour downstairs has identical model and has been running as sealed from new (approx 20 years ago!). Mine was open vented from new due to loft space being available (top floor).

Ed's FAQ mentions the boiler needing "secondary overheat protection". Is there any way I can check? I can't see any reset button on the boiler itself ? Could this be an additional component that would only be fitted to the boiler in the event of it being used for sealed operation ?

Also, is it insanity to try and pressurise an old boiler? All existing rads have been replaced, underfloor pipe work in good condition so leaks there should not be a problem.

My only reason for wanting to run the old system temporarily is that when I get quotes for the new boiler the existing system is proven as working.

Thanks for any help with this.

[Ed Sirett]

I used to have a GW Galaxy BBU - in fact its still in place except for the gas valve and burner. It did not have any form of overheat cutout and I doubt yours has.

Operating this sort of boiler on a sealed system is outside the permitted use and therefore: a) illegal. b) possibly dangerous.

Thermostats can and do fail on these sort of boilers - let's say it had a

50% chance of going in the next 100 months? That's plausible given its current age. The boiler will then boil. Steam will be raised. The pressure fluctuations will be intense and could well do some damage - it'll let everyone know something BAD is happening. The steam will be sent out then the boiler is dry! So you will then have an empty boiler being roasted.

Also Gas valves could in principle jam on. The pilot valve would be able to shut the boiler down automatically but only if there is an o/h cutout.

The noise of a _vented_ boiler going uncontrolled is bad enough that all people it happens to (i've met so far) don't want the old one repaired! They view it with suspicion from then on.

[andy.hide]

Thanks Ed. I had my doubts about doing this hence my question so will hold off on the sealed conversion until the new boiler is fitted.

Andy.

Ed Sirett wrote:

[Set Square]

If your new boiler is a system boiler, it will duplicate many of the components which you would have to buy to convert to pressurised, anyway.

If you're worried about testing the existing system, could you temporarily disconnect the F&E tank and pressure test the pipework - cold, of course?