Baxi Expansion Vessel Query

[Syd Rumpo]

The expansion vessel integral to our Baxi Megaflo System 32HEA boiler has failed, and so the pressure varies wildly.

No problem, looked up the part number and bought one to fit today.

On opening the boiler, it became apparent that the existing vessel was

10 litres whereas the one I bought was 8 litres. I fitted it anyway, thinking that a working 8 litre vessel is better than a dead 10 litre vessel.

All seems to be well, but I do wonder why the original installer fitted a 10 litre part if the standard part is 8 litres. Am I going to die in some horrible revenge-of-the-corgis incident?

Cheers

[Tim+]

The expansion vessel should be sized to the water capacity of your CH system, not just to the boiler output so it's quite possible that different sized vessels are available for that boiler depending on it's application.

That said, if the pressure changes are okay, I wouldn't worry about it too much.

Tim

[Andrew Gabriel]

Maybe standard was 10 litres at the time.

The consequence of a smaller one is that you will get larger pressure swing between system being cold, and system running at max temp. Providing the swing is still within the operating range, that's fine.

You can always add an extra one anywhere on the central heating circuit. (There should be one near the pump inlet, as that reduces wear and noise on the pump impeller, but if the pump and expansion vessel are integral to the boiler, the integral one will serve that role.)

[Syd Rumpo]

Thanks Tim and Andrew. I thought it would be ok, and am encouraged that you both think much the same.

Cheers