Selectra® systems from Maxitrol maintain precise, stable gas-fired temperatures. Selectra's unique electronic Modulator or Modulator-Regulator valves control gas flow with instantaneous response and continual adjustment. They are the superior alternative to mod motors and butterfly valves. OEM or retrofit applications include environmental climate control, as well as industrial or commercial heating processes. Standard temperature adjustment range 55° to 90° F. All fuel gases are compatible - capacities to 30,000,000 Btu/h.