Johnson Controls W43A-14 Humidistat

The Johnson Controls W43A-14 Humidistat is a commercial-grade dehumidification controller designed for precision moisture management in HVAC systems. Engineered for high-voltage applications, this SPDT electromechanical humidistat supports 120, 208, and 240 VAC circuits, making it highly versatile for various field installations. It features a broad 0 to 70% RH range with a fixed 5% RH differential, ensuring stable cycling and preventing equipment short-cycling. The W43A-14 utilizes a high-sensitivity cellulose nylon sensing element that provides reliable accuracy even in fluctuating environmental conditions. The unit is designed for flexibility, supporting both vertical and horizontal mounting to accommodate tight mechanical spaces. This model is a direct replacement for the W43A-14C, sharing identical technical specifications and footprint. Contractors typically utilize this control for exhaust fan activation, power damper operation, or interfacing with commercial dehumidifiers to maintain optimal indoor air quality and structural integrity.

Technical Specifications & Key Benefits

• Universal Voltage Compatibility: Operates on 120/208/240 Vac for seamless integration into diverse electrical layouts.
• SPDT Switch Action: Allows for "make-on-rise" or "make-on-fall" wiring, supporting both humidification and dehumidification sequences.
• Robust Sensing Element: The human hair/cellulose nylon element ensures consistent calibration and long-term stability.
• Flexible Installation: Features a dual-scale dial for easy adjustment regardless of mounting orientation.
• Commercial Build Quality: High-impact plastic cover protects internal mechanics from dust and debris found in mechanical rooms.

Common Questions from the Field

Is the Johnson Controls W43A-14 compatible with low-voltage systems?
The W43A-14 is primarily a line-voltage controller designed for 120V to 240V AC. For 24V applications, ensure the current draw does not exceed the inductive rating of the SPDT contacts or use a transformer-relay combination.

How do I calibrate the 5% RH differential?
The differential on the W43A-14 is factory-set at 5% RH and is not field-adjustable. This fixed range is optimized to provide a balance between precise humidity control and mechanical longevity of the switching components.

Can this humidistat be used to control an exhaust fan directly?
Yes, the SPDT action allows you to wire the fan to the contacts that close on a humidity rise, making it an ideal choice for moisture-triggered ventilation in commercial kitchens or storage facilities.

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.