A burner unit includes first and second burner assemblies supplied with a gas mixture via first and second valves, respectively. A first valve control assembly controls the first and second valves between open and closed positions. Third and fourth burner assemblies of the burner unit are supplied with a gas mixture via third and fourth valves, respectively. A second valve control assembly controls the third and fourth valves between open and closed positions. The first and second valve control assemblies are separate assemblies that are configured to cooperate to simultaneously provide a gas mixture to the first, second, third and fourth burner assemblies in respective high power settings of the first and second valve control assemblies.