Hello all, 1st of all I am NATE certified and have a full EPA recovery license. I have been around refrigerants and propane/natural gas for 7 years. Then I got layed (2.5 years ago) off and dad passed away...... Fortunately, the boilers in 2 houses fired right off. The 3rd apartment house has 5 forced hot water (converted radiators) and 4 fired right off from cold ass they should. Those 4 all have original Honeywell controls. I tried to get a full flame on #5 and it would only do so if I closed the thermostat or put it on manual. Dad replaced the aquastat just last December (tenant said she froze) and I think he wired it wrong or has the wrong aquastat. Anyhow, we have Burnham boilers. The one that feeds the 3rd floor that Dad put an aquastat on is a high limit aquastat. Honeywell L8148J - Which appears to be a high limit stat. It seems to have no low limit or "Keep the boiler at 175-190 degrees" or it is the wrong stat and wrong application. I wonder what a high limit stat is actually for?? So, from dead cold, it won't go to operational parameters without me placing it on manual or jumping the stat. That means every time that tenant turned up her stat, it had to go from 20-40 degrees to circulating temperature. The boiler should be at 180 all the time........ Did Dad put in the wrong aquastat? Do hi limit aquastats have a low limit (is it cooked?) This boiler as the other 4 did should have run 20 minutes to start the season and then maintain there set points; However, something is wrong here. Thank you so much for any help. I am very use to a multimeter/gas/HVAC etc etc. I just don't know if this is broke or incorrect.