Markings on older gas valves

Mike Kusiak_2

Looking a the photos of older diaphragm and solenoid gas valves on this site and elsewhere. I noticed markings like 1/2" SM, 3/4" small, 3/4" large, 3/4" LG, etc. What do the small and large designations refer to? Gas carrying capacity, thread or physical size?



Were there published ratings based on these designations?

Tim McElwain

These had to do with the

size opening internally in the gas valves at the gas valve seat area. This determined what today we call standard capacity valves and the larger internal openings high capacity valves. Many times the actual size of the valves would be say 1/2 " by 1/2" and the internal opening would be 3/4". Thus we have a 1/2" by 1/2" valve with a higher capacity than a 1/2" by 1/2" with only a 1/2" valve seat opening. A lot of this was done so OEM's could meet testing standards set by ANSI for size versus capacity.



We have had valves over the years for residential design purposes that went as high as 1", 1 1/4" and 1 1/2" giving as much as 600,000 BTU's. It was always an issue in certain areas as to the higher capacity valves being commercial/industrial valves but that is not so just higher capacity valves. The American Gas Association determined that any system over 400,000 with Flame Safeguard Controls was commercial industrial. You could however have much more BTU and stay within residential standards. I in fact have an old BRYAN boiler in the East Side of Providence that I care for that is 1,250,000 and is classified residential. It has three pilots and two gas valves all of which were converted by myself many years ago to Powerpile. Those valves are 1 1/2" valves. 



Mike I do not know exactly what valves you are referring to but yes some had published maximum BTU or CFH (Cubic Feet per Hour) ratings in the catalogs.

Mike Kusiak_2

Ratings

Thanks for the explanation Tim. I guess my question regarding ratings was a bit ambiguous. What I really meant to ask was did a size like 1/2" small imply a specific BTU rating of the valve. For example did a Honeywell 1/2" small valve have the same BTU rating as a White Rodgers 1/2" small?



Sure seems a lot less confusing these days when valves are specified directly by their BTU capacity.

Tim McElwain

No they are not

all the same. Different valve manufacturers listed max and min capacity based on allowable pressure drop through the valves. There are charts for all gas valves today which give such information.



If you had the old catalogs they would be listed.

Tim McElwain

Mike, that valve

White-Rodgers F 26A02-204 would pass 340 Cubic Feet Per Hour at 1" W.C. allowable loss.

Mike Kusiak_2

Ratings

Thanks for looking it up Tim.



I am glad you still have your old catalogs, as info like this doesn't seem to be available anywhere else.

Tim McElwain

Mike actually

I could not find it in my old catalogs.I have a contact at White-Rodgers who helps me with these questions so it came direct from him. I ask him if they had any cross references that give that info and he said no. He got the info off the old spec sheet for the valve which he told me should still be in the box with the control unless someone took it.