The SC30-SM2 Series signal conditioner, used with the M420, M520, and M620 series modulating gas valves, is designed to modulate atmospheric indirect fired heaters that have a sectioned gas manifold and 2-speed inducer.

The sectioned – or split – manifold design operates as two independent manifolds sharing a single 2-speed inducer. One manifold section is fully modulating and the other section operates as a 2-stage. Typical applications achieve a turndown of approximately 10:1.

SC30-SM2 Series System Features

  • Fixes the modulation output voltage and SPDT inducer relay for a predetermined time after receiving EST VDC input.
  • Conditions temperature control signal to:
    • Control Maxitrol M Series modulating gas valve.
    • Energize/de-energize SPDT Relay 1 – sets inducer speed to high or low position.
    • Energize/de-energize NO Relay 2 and Relay 3 – activates high and low stage of non-modulated section.
  • Maintains 100% modulation rate for selected time after Relay 2 is energized.
  • Limits minimum VDC to modulator when non-modulated section stages become active.
  • SC30-SM2A Models: Fixes M Series modulating valve VDC and de-energizes Relay 3 when desired AFS VDC input is not present.

For more information or to schedule a product demonstration, please contact your Maxitrol Company Sales Representative.


Signal Conditioner SC30-SM2
SC30-SM2 Signal Conditioner