Cut-in confusion

William Faust

My 2-pipe steam system was installed around 1950. It now uses a boiler feeder. The design pressure drop, using pgs. 12 and 128-130 of Holohan's TLA, was almost 3 ounces on the nose.

1) Does the cut-in have to be double the pressure drop on pumped systems?

2) If so, why? Hollohan's book mentions the "safety factor" at the top of pg. 130, but I don't understand that issue.

3) If not, Hollohan says on pg. 106 that a cut-in should not be less than 1/4 lb. = 3 oz. Why? What effect would there be if, say, I used a cut-in of 1 ounce?

In a nutshell, I want the lowest Vaporstat cut-out possible but I also want the lowest possible cut-in, my purpose being to maximize the differential so that boiler short cycling is minimized.