Ravenheat RSF 820/20 T Part Identification

Would someone be kind enough to identify the spherical part in the photo of my Ravenheat boiler (and its purpose).


And from another angle


My thanks in advance.

HI

hot water expansion vessel ?

It's a mini expansion vessel to prevent excessive high pressure buildup in the DHW circuit when the heating is used. In reality the majority of these vessels are completely flat after a few years and if your stopcock is fully open (and doesn't have a loose jumper) you're unlikely to have any problems so leave well alone.

If there are any non return valves before the boiler the vessel should be checked for pre-charge. However you need a compressor to pump it up or take the unit it to a garage....you can't use a foot pump.

Thank you. Makes alot of sense. And yes I have no intention of interfering with it. Would be interesting to know however what the symptoms would be if it were faulty.

Reason for asking was when I examined the boiler schematic there seemed to be no reference to it. Even now I'm struggling to see it.

Ironic it's an expansion vessel as I've only just repressurised the main expansion tank (with a foot pump) due to fluctuating boiler pressure. Done the trick nicely; I really am hoping the vessel just lost pressure over the many years it has been installed rather than the rubber diaphragm has a slow leak. Time will tell.

Once again many thanks for a comprehensive reply.