My boiler settings

Leonard

Wondering what temp I should set my aquastat hi/low and differential settings at ?
Also wondering what "differential" setting on it refers to.
( #'s from under aquastat cover L8124A,C L8151A)

Few months ago had cool shower, I compensated by upping the aquastat temps. Now I tracked down problem to leaking DHW mixing valve and fixed it, but didn't mark the original settings.

I also notice the temp/pressure gauge on top of boiler reads about 25 degs higher when burner shuts off than the aquastat high setting. Sounds like one of them is off.

Have force hot water heating with tankless DHW ( copper coil in water jacket), cast iron base boards running perimeter of house ( ~12inch high x 2 thick, cast fins on backside), monoflow system (boiler supplies far end of loop and water returns along both sides of loop). I only heat 1-st floor, 1-st floor alone is 1,500 SF. 2nd floor is unfinished and not heated

59 year old oil fired boiler , National Sunray IV , boiler # 5-19A/O/OP , rated 128k BTU/hr 1.6 gal/hr
Original oil burner National -US model NB2-K2, firing rate .85-2.0 gal/hr , nossle is either ~1.26 or 1.35 gal/hr

Boiler is on cellar floor, chimney extends from cellar floor thru 1-st & 2nd floor , and another ~ 5ft thru peaked roof, plus another ~ 3 ft over roof.

Len
Mechanical Engineer