not plumbing /heating really but maybe of interest,been to do landlord safety cert today front and rear lounge fitted with identical cannon tacotta brass effect ilfe's, passed flue & spillage on both fires ok,however the ffd on the rear fire was just about slamming shut barley just under 180 secs,and the front one shut at 42 secs,nothing in the mi's so rang canon they told me that (quote) "it didnt have a set time to go off" and in any case they don't give out that kind of information,they were as much use as a chocolate fireguard!!! anyway i left it turned off till i can clarify the specs for the ffd. BETTER SAFE THAN A DEAD BODY !