40,000 to 220,000 BTU/h. Natural Gas and LPG. Configurations of U and L, horizontal or 45°. Separate controls compartment – electronics out of air stream, the burner can run during servicing. Self-diagnostic ignition module. Parabolic aluminum reflectors - most efficient in the industry. Direct spark ignition. Vented or unvented. Operating status lights. 24v direct wire for the thermostat.