The boiler is a Delco DB4S...I'm getting mixed info from the heating museum and the old booklets as far as the BTU's...ranges in books and brochures.....121000 to 160080 boiler output..with 39.5 boiler capacity. This is a 2 family house...there are no vents in the system...the expansion tank has a drain faucet on the tank and no other gauges attached...There are 15 radiators in the house....there is one taco circulator feeding the system.
The burner is a Beckett AF with and F3 head 1.25 gph 80 degree Hollow. The burner is running fine. I just installed new vent pipes and barometric damper...brushed and cleaned the boiler...checked everything.
I drained the tank....which is an old B & G tank on ceiling....diameter is 12 inches and length is 30 inches...I figure it was just under 15 gallons. I tested it using the B & G dual valve instructions...The boiler was off for a few days...refilled the tank and the valve filled it up to 12 lbs on boiler pressure gauge.
Started the boiler and after 10 or so minutes the pressure went to 15. The book said if it's over 10% of total boiler pressure cold that the the tank is no good.
I've seen the safety valve leak some water last heating season when the pressure was in the high twenties. and figure this tank is no good anymore..unless I'm wrong...I'll change all those valves if necessary if the tank turns out to be the problem here.
I'm figuring all radiator volumes, pipes, boiler volume...etc...but it seems when I call to ask for a replacement I'm told anywhere from 4 gallons to 20 gallons..Some say the diaphragm type is smaller...none that mount on the ceiling...
Is all this math and calculation the best way to go..or is it just overkill?
Just read the below article on this site written by Dan...good and informative info here. After the responses from this post and reading this article it looks like there is hope for this tank.https://heatinghelp.com/systems-help-center/why-compression-tanks-waterlog/
(The comment below is about a steam system I worked on and has nothing to do with this post)
I did have to measure every steam pipe in a house and figure out all the capacities to figure out the proper venting for the basement as well as all the radiators so I know how to figure out the formulas on that kind of stuff. I read about all that here on this site thanks to information leading to Gerry Gill's information...and also attended a Steam Lecture by Dan Holohan in NYC.
How should I proceed with this please?