I recently posted and found the forum exceptionally helpful so decided to post again. Thank you everyone for your help and responses! We recently moved into a two-family building with two Burnham steam-fired boilers in the basement. Each apartment/unit is about 1,000 square feet. We live in the bottom unit and our monthly winter bill has been about a couple hundred dollars, but the upstairs unit has been nearly twice that. The building is not insulated (although the attic is), but I would imagine that should impact both of us relatively equally. I took a look at the upstairs' unit boiler, and the water level was below the bottom level of the look-through glass (see image below) while it was running; as in, I couldn't see any water in it (in our boiler, I can always see water in the glass, even when it's running). As soon as the boiler turned off, the water level rose a bit, I would say two inches from the bottom (see second image). I also noticed the auto-feeder light is not on, while the low-water cut-off light one is on, so I'm not sure if the auto-feeder is not working (see third image).
I was wondering if the forum could help us with a couple questions:
1. What is the appropriate amount of water that should be in the system while it is running? Should I be able to see it in the glass while it's on?
2. How do I know if the auto-feeder is working or not? Should I press the "reset" button?
3. What might be other causes of this significant difference in heating costs between the two units that I should investigate?