This is an old photo of the garage which also shows the furnace room already in place. The furnace room was constructed during fall of 2003, in preparation for winter. Its walls are insulated with fiberglass to keep cold air out and maximize the use of the warm air the furnace produces.
When you enter the furnace room this is what you will see: the furnace (which Gary covers with insulation materials as well), and the oil burner (blue, on the left). The two are connected, with the hot water coursing through the copper pipes. The silver pot-like thing above the furnace is the expansion tank. It has a rubber valve inside, with air on one side and hot water on the other. It serves to "absorb" the fluctuations in volume (since the furnace goes from cold to hot to cold, creating volume expansion/shrinking depending on the temperature). The expansion tank maintains the pressure at 10 psi. Without it, there is the danger of explosion secondary to very high steam pressure if water/air gets too hot.
This is a better view of the side where the oil furnce is, with its own expansion tank. During the early days we placed our upright freezer inside the furnace room (I asked hubby if it would not do harm that the freezer is placed in the hot furnce room. He said the freezing cold air in the garage would do more damage.) Those circuit boxes behind the expansion tank are relays getting signals from the low-voltage thermostat to the high-voltage furnace. (I'm not sure if I got it right...that's what I got from hubby's explanation...haha!)