SINGLE STACK 2 SWITCH SEQUENCE

What it is

• Brand: Supco (NSI Industries / Thermodisc lineage)
• Type: HVAC heat sequencer (relay timing control)
• Function:
  • Staggers electric heat strip activation
  • Controls blower/aux heat timing
  • Prevents inrush current spikes in electric furnaces

Key specs

• Control voltage: 24V
• Switches: 2-stage sequencing
• Timing:
  • ON delay: ~30–90 seconds
  • OFF delay: ~1–30 seconds
• Use cases:
  • electric furnace heat strips
  • air handler auxiliary heat
  • multi-stage resistance heating systems

How it compares in your list

• Q104 = 2-switch sequencer
• Q105 = 3-switch sequencer (more stages)
• Q107 = similar function but different staging/timing configuration