Integrating a humidifier with your Nest Learning Thermostat 4th Gen can enhance your home comfort, especially during dry seasons. However, improper wiring can lead to operational issues and potentially damage your thermostat. This guide delves into a practical approach to wiring your humidifier, drawing insights from the Nest Learning Thermostat operation manual to ensure a safe and effective setup. We’ll explore a configuration that addresses potential current load concerns and ensures seamless integration.
Addressing Potential Current Draw Issues with Solenoid Valves
One user encountered an issue where directly connecting their Aprilaire 560 humidifier’s solenoid valve to their Nest Thermostat seemed to cause problems. The solenoid valve, responsible for controlling water flow to the humidifier, exhibited “chattering,” indicating a potential electrical incompatibility. This ultimately led to damage to the Nest Thermostat, suggesting that the thermostat might not be designed to handle the current draw of certain solenoid valves directly.
While specific circuitry details for the Nest Thermostat are not readily available, the Nest Pro Installer Guide offers valuable guidance. This manual becomes a crucial resource for understanding recommended wiring practices, especially when integrating accessories like humidifiers.
Leveraging the Nest Pro Installer Guide for Optimal Wiring
Referring to the Nest Pro Installer Guide, specifically the configuration detailed on page 35 titled “Built-In Humidifier System, 2 Wire”, provides a robust solution. This configuration, with a slight modification, forms the basis for a safer and more reliable humidifier setup with your Nest Learning Thermostat 4th Gen. The key modification involves connecting the HUM2 terminal to the common wire, adapting the standard diagram for specific system requirements.
To mitigate potential current draw issues, implementing a relay is highly recommended. A White Rogers 90-290Q 24 VAC relay, as suggested in the manual, acts as an intermediary, isolating the Nest Thermostat from the direct current demand of the solenoid valve. This approach creates two distinct circuits: a low-current control circuit managed by the Nest and a high-current circuit powering the solenoid valve.
Detailed Wiring Configuration with a Relay
This configuration employs a relay to manage the higher current demand of the humidifier solenoid, protecting your Nest Thermostat. Here’s a breakdown of the two circuits involved:
Control Circuit (Low Current)
This circuit is responsible for activating the relay and is controlled by the Nest Thermostat. The wiring is as follows:
Nest * (Humidifier Output) to White Rogers 90-290Q Relay to Furnace COM (Common)
When your Nest Thermostat calls for humidification, it sends a 24VAC signal through its designated humidifier output (labeled as Nest *). This low-current signal energizes the White Rogers 90-290Q relay, effectively closing the relay switch and enabling the high-current circuit.
High Current Circuit
This circuit provides the necessary power to operate the Aprilaire 560 solenoid valve and is powered by the furnace’s HUM output. The wiring is configured as follows:
Furnace HUM (Humidifier Output) to White Rogers 90-290Q Relay to Aprilaire 560 Solenoid Valve to Furnace COM (Common)
This circuit becomes active when both the furnace HUM output is on (typically when the furnace burners are ignited) AND the Nest Thermostat activates the relay via the control circuit. The relay acts as a switch, allowing current to flow from the furnace’s HUM output to the Aprilaire 560 solenoid valve only when both conditions are met.
In essence: The Nest Thermostat triggers the relay (low current), and the relay, in turn, allows the furnace’s HUM output to power the humidifier solenoid valve (high current). This indirect control method safeguards the Nest Thermostat from potential electrical stress.
Additional Wiring and Configuration Notes
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Nest Configuration (AQ+/AQ-/*): While the example configuration utilizes the Nest * output for the humidifier, the Nest Thermostat operation manual may offer flexibility in assigning AQ+ or AQ- terminals for humidifier control. However, aligning with the manual’s recommended configuration is generally advisable for straightforward setup.
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Thermostat Wiring: Typical Nest Thermostat wiring includes terminals such as Y1 (Cool), W1 (Heat), G (Fan), C (Common), and Rh (Power). The humidifier control is added using the designated output (in this case, Nest *). It’s important to note that some systems may not utilize a common wire (C wire), and wiring configurations can vary depending on your specific furnace and thermostat system. Always consult your system’s documentation and the Nest Learning Thermostat 4th Gen Operation Manual for accurate wiring guidance.
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Furnace and Humidifier Wiring Compatibility: Identifying the furnace’s HUM output is crucial. This output typically provides 24VAC when the furnace burners are active. Using a voltmeter to confirm the voltage between the suspected HUM output and the furnace common terminal is a recommended safety measure before proceeding with wiring. The HUM output may activate concurrently with the burners or under slightly different furnace operating conditions, which should be considered for proper humidifier operation.
Conclusion
Properly wiring your Nest Learning Thermostat 4th Gen with a humidifier requires careful consideration of electrical compatibility and adherence to recommended practices. By referencing the Nest Learning Thermostat operation manual and employing a relay-based configuration, you can effectively manage the humidifier’s solenoid valve while protecting your thermostat from potential damage. This approach ensures reliable and safe operation of your home humidification system, contributing to a more comfortable and healthy indoor environment. Always prioritize safety and consult with a qualified HVAC professional if you have any doubts or complex wiring scenarios.
