High psi limit turns off the burner, when the psi exceeds a preset level, usually 5 to 7 psi it will turn the burner off. The low water cut off shuts down the burner when the water level is to low. Sorry so cranky I think I posted that around 4AM. I didn't have my Coffey yet beenthere. God bless.
Steam can be quite safe if controlled correctly however A Steam Boiler can become a Steam explosion in very short order if incorrectly controlled.
Call your local equipment supplier or supply house and see if they can get you the Armstrong or ITT Steam Boiler literature. As stated, apply for pro membership (It's FREE) and there are a wealth of experts that will be glad to help you in the pro forums.
(BTW, residential steam boilers seldom have aquastats)
It's not to frustrate you but to protect others with limited experience from possibly damaging equipment, property or even getting themselves and others hurt or , worse, killed !
There was a guy a couple of years ago (that lived 6 miles from my house) that got electrical advice off the Internet and nearly burned his house to the ground all because he didn't understand all the information. He wasn't dumb just ignorant !
Becareful with Steam, it can be dangerous !
If sense were so common everyone would have it !
All opinions expressed are my own. Any advice provided is based on personal experience, generally accepted fact or publicly available information. As such, it is worth exactly what you paid for it, not a penny more not a penny less !!