York S1-THEH21NS Thermostat

Upgrading or replacing a residential control interface requires a reliable, no-nonsense solution like the York S1-THEH21NS Thermostat. This Source 1 OEM thermostat is a non-programmable heat pump thermostat engineered for single-stage cooling and two-stage heating (2H/1C thermostat) applications. Designed to meet strict original equipment specifications, it ensures precise temperature regulation without the complexity of modern scheduling interfaces, making it the preferred choice for tenants or homeowners who prioritize simplicity and consistent performance.

The S1-THEH21NS is versatile regarding power, operating on 24VAC system power or dual AA alkaline batteries for reliable backup. It features a large, high-contrast LCD for easy legibility in low-light environments and includes an auxiliary heat indicator to notify the user when the second stage of heating is active. For technicians, the unit is straightforward to commission, with standard terminal designations (R, C, Y, W, G, O, B) that simplify heat pump thermostat wiring during field replacement or new installations in light commercial and residential settings.

• OEM Reliability: Genuine Source 1 component ensures exact compatibility with York, Coleman, and Luxaire heat pump systems.
• Dual Power Capability: Flexible installation using 24V hardwire or battery power for systems without a common wire.
• Simplified Interface: Non-programmable logic eliminates "reset" service calls caused by user programming errors.
• Robust Stages: Optimized for 2 Heat / 1 Cool configurations, including emergency heat management.
• Permanent Memory: Setpoints are retained during power failures, preventing the need for site visits after local outages.

Is the York S1-THEH21NS compatible with dual fuel systems?
This thermostat is primarily designed for standard 2H/1C heat pump systems. For dual fuel (fossil fuel kit) applications, verify your specific wiring requirements, as this model utilizes standard O/B reversing valve logic.

Does this unit require a "C" wire?
No, a common wire is optional. The unit can be fully powered by two AA batteries, though connecting to 24VAC is recommended for long-term maintenance-free operation.

Can I use this for a 2-stage compressor?
This specific model supports 2 stages of heat (typically compressor plus auxiliary heat) but only 1 stage of cooling. It is not intended for two-stage cooling equipment.

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.