A. GARELECK & SONS, INC.
PLUMBING & MECHANICAL
125 Arthur St
Buffalo, N.Y. 14207
They are also referred to as on demand hot water heaters because they don't usually store hot water, but rather create in on demand. They come in point-of-use and whole house versions and there are electric tankless water heaters and natural gas or propane models.
The boiler is essentially a closed vessel inside which water is stored. Fuel is bunt in a furnace and hot gases are produced. These hot gases come in contact with a water vessel where the heat of these hot gases transfer to the water and consequently steam is produced in the boiler