In message .uk, Ed
Sirett writes

I have no reason to doubt raden's belief that these boilers have
troublesome fans.

No, that's Fuelsavers, the Spacesaver has a completely different fan

... if any fan at all.

Well, yes

From where I stand, If I know there's a Fuelsaver fan, I don't
necessarily know that there's a version without a fan

--
geoff