PVI Industries' MAXIM is a fully packaged gas- or oil-fired vertical firetube water heater. Combustion occurs below the water storage tank, and the hot combustion gases move upward through the firetubes, transferring heat by convection into the stored water. Baffles in the firetubes create turbulence in the gases, forcing more frequent contact with the tube walls and helping to raise thermal efficiency to 83%. Combustion is provided by a power burner with electronic sequencer and flame safeguard. Water temperature and burner operation are controlled by submerged upper and lower operating thermostats and a submerged high limit control. PVI Industries.