Schneider Electric (Barber Colman) AT-603 Subbase

The Schneider Electric (Barber Colman) AT-603 Subbase is a precision-engineered mounting platform designed for single thermostat selector switch applications. Built for professional HVAC technicians and contractors, this dual switch thermostat subbase provides the essential interface for complex environmental controls, specifically accommodating most single electric room thermostats. The unit features a robust architecture housing one DP4T switch and one DPDT switch, allowing for versatile manual or automatic changeover between heating and cooling stages. When performing a field replacement or new installation, this subbase ensures a secure foundation for 24V or 120V AC control circuits, supporting high-load ratings such as 5.8 Amps at 120V. Its integrated selector switch subbase design is ideal for unit ventilators, fan coil units, and packaged terminal air conditioners (PTAC) where localized multi-stage control is required. The beige plastic housing is UL approved and designed for flush or surface mounting on standard electrical boxes, streamlining HVAC thermostat accessories integration while maintaining strict compliance with national and local electrical codes.

• Multi-Switch Flexibility: Features a dual-switch configuration (DP4T and DPDT) to manage complex multi-stage heating and cooling sequences.
• Broad Compatibility: Engineered for use with nearly all single electric room thermostats, excluding only specialized models like the TC-114 and TA-121.
• Professional Electrical Capacity: Rated for pilot duty (125 VA) and non-inductive loads up to 6 Amps, meeting industrial performance standards.
• Rugged Reliability: Constructed with high-industrial-grade materials to withstand the heavy-cycle demands of commercial climate control systems.

Which switches are included with the AT-603?
The unit comes equipped with one DP4T (Double Pole, Four Throw) and one DPDT (Double Pole, Double Throw) switch. Note that legend plates for labeling (e.g., Heat/Cool/Off) typically ship blank and are configured during field installation.

Is this subbase compatible with all Barber Colman thermostats?
It is compatible with all single electric room thermostats except for the TC-114 and TA-121 series. It is a direct replacement for the legacy AT-603 and AT-603-756 models.

What are the voltage and amp ratings for the AT-603?
The subbase is rated for 24V to 240V AC applications. At 120V AC, it handles 5.8 Amps full load and 34.8 Amps locked rotor. At 240V AC, it is rated for 2.9 Amps full load and 17.4 Amps locked rotor.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.