On Tue, 7 Dec 2010 07:21:20 -0800 (PST), Jethro wrote:
Never noticed one on my Vaillant 820 TurboMax boiler ... can they be
internally fitted, or not always required ?
Only condensing boilers need one, I don't know if that particulary
boiler is a condensing boiler.
More info:
http://www.diyfaq.org.uk/plumbing/he...ngsystems.html
http://wiki.diyfaq.org.uk/index.php?...iler_Evolution
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Cheers
Dave.