Patent ID: 7681536

Claim:
A fluid heater, comprising metal tubing edge-welded together to construct a combustion chamber floor through which fluid to be heated is circulated along a circuitous path until the fluid enters a bottom of a combustion chamber wall mounted to the combustion chamber floor and forming three sides of a combustion chamber with a fourth side formed by a combustion unit, the combustion chamber wall being constructed of rectangular steel tubing edge-welded together to form a circuitous flow path up through the combustion chamber wall, and a coil stack chamber above the combustion chamber constructed of edge-welded metal tubing, the edge-welded metal tubing of the combustion chamber floor, the combustion chamber wall and the coil stack chamber providing a first part of an uninterrupted flow path between an inlet and an outlet for the fluid to be heated, and a coil stack supported above the combustion chamber within the coil stack chamber, the coil stack forming a second part of the uninterrupted flow path and providing a circuitous path for the fuel to be heated through which flue gas is exhausted from the combustion chamber.