Boiler feed valve

cadec

So I understand the idea of installing the feed valve at the location of zero pressure change, but some guys however will argue this till they are blue in the face and insist on installing this feed valve on the return side at the bottom of the boiler. Arguing that it's better to feed from this location, that filling a boiler from the top has a better chance to shock it than feeding from the bottom and also that this is better for air elimination. Any help on this topic would be great.

Fred

The purpose of feeding water into the return is that cold supply water is tempered by the return water in the returns before it enters the boiler. Cast iron boilers are very susceptable to temperature shock and possibly cracking or developing hairline cracks. that little bit of tempering helps prevent that. Adding it at the top of the boiler, typically (at least for steam boilers) means adding it to an area of the boiler that can be steam hot and with no water in that area to temper the cold water as it hits the sides/top of the steam chest. I once put a cast iron skillet in the refrigerator and then took it out and put it into a pre-heated oven. Needless to say, that skillet cracked down the middle and about half way across.

cadec

Thanks guys very helpful.

j a_2

Obviously your speaking of a hot water boiler and not a steam boiler....Correct? The installation manual will show u exactly where they want it...in the piping section of the manual....The book available here is called pumping away and it's a good read...it explains clearly how and why boilers are piped....Fill valves are just that, fill the system and shut it off..

Fred

I agree @j a , The manufacturer specifies where the supply valve should go, and they do so for a reason, be it hot water or steam. Anyone stupid enough to do otherwise gets what they deserve, sooner or later, unless they are doing that work on some elses boiler and simply don't care and can walk away leaving that homeowner out on a limb. Most people know that hairline fractures can occur as a result of temp shock, even though they may not leak, immediately, they weaken the structure of the boiler block, not to mention the position of the homeowner when he/she needs to initiate a warranty call for a failed block.

j a_2

Yup, why take the chance being being Mr.Wizzard...go by the dam book and you can't go wrong....I love the people that think they know better, than the manufactures....