When sizing a boiler, how do you determine which size boiler to purchase? If a house calls for 80,000 btu's, what am I looking for? Example: Biasi SG2 Is it DOE heating capacity (79,000)? Or is it Net Output (69,000 MBH)? :confused:

I have a Utica (peg112cde) gas fired steam boiler that has a McDonnell uni-match (wf2-u-24) low water autofeed (better safe than sorry w/tenants). The low water shutoff is also made by McDonnell (ps-805 u-24). My issue is that when the boiler's water level goes down after around 30 or so heat cycles due to normal radiator steam release, the water level is sufficiantly low enough to trigger the autofeed but it overfills the boiler, ie, the water in the sight glass is all the way up & just into the valve on top when the steam condenses back into water. I've looked for some sort of adjustment but can't seem to locate one on either the autofeed or the low water shutoff. This can't be normal (it fills the boiler way above the recommended max water level sticker behind the sight glass). Any suggestions? Thanks, DAS :confused: