the house is a 3 family apartment built in i think 1908. there are 3 floors. The furnaces are in the basement.
There are 3 of them one for each floor. There are 4 hot water tanks in the basement as well one for each floor and one for the wash machine i believe. We just turned the furnaces on for the winter. The landlord likes them off in the spring + summer. The hotwater tanks are like this but this isnt a picture of my tank its like that one.
http://www.cpsc.gov/cpscpub/prerel/prhtml08/08241A.JPG
In a furnace, flue gas acts on a heat exchanger full of air that is then circulated directly through the house. That's not what you have.
In your building, the space heating is done by gas boilers. The hot flue gas acts on a heat exchanger filled with water. The water is then pumped to the radiators.
The tank that you showed me is a domestic hot water tank. It heats your water that you use for washing. These systems are unrelated to the space heating systems.
Does the boiler heating your floor have one zone or several. I'm guessing that it is one. You could, however, have two or more loops as I described for my ranch home. Each loop should have an air release valve located at its highest end, as well as a separate hand-operated valve that can be used to reduce the flow through that loop. These can also be used to diagnose and sometimes solve problems.
