All Heavy-Duty Commercial Gas units have a glass coated internally-lined tank fired at 1600°F. This provides a tough interior surface for storage tanks and maximum protection against the wearing effects of high-volume and high-temperature water. Ideal for most medium to heavy duty commercial applications requiring a motorized flue damper. Motorized flue damper Non-CFC Polyurethane Foam to prevent heat loss and reduce energy costs Fused Ceramic Shield Tank for anti-corrosion protection 24-Volt Thermostat Control Electronic Thermister Sensor (Price subject to change without notice. Check stock before order)