Adjustable Capillary Thermostat (0–90°C / 32–194°F) for Durvela Solar Aeration Fan System

• Designed for the Durvela Solar Aeration Fan System.
• Compatible with the Durvela 12 VDC, 6 W aeration fan.
• Controls fan operation from either the solar panel or DC backup adapter.
• Compatible with the maintained SOLAR/OFF/ADAPTER selector-switch circuit.
• Intended for installation inside the Durvela solar aeration fan enclosure.
• Replaces the original adjustable capillary thermostat used in the Durvela system.
• Not intended for AC mains wiring or unrelated heating and cooling equipment.

• Adjustable temperature range from 0°C to 90°C (32°F to 194°F).
• Automatically starts the aeration fan when the selected temperature is reached.
• Mechanical capillary sensing requires no separate electrical power.
• Remote sensing bulb measures temperature away from the thermostat body.
• SPDT switching contacts with COM, NO and NC terminals.
• Supports both solar and DC backup operation.
• Simple mechanical adjustment without programming or electronics.
• Designed for reliable low-voltage fan control.
• Replaceable and serviceable using standard terminal connections.

• Product type: Adjustable mechanical capillary thermostat
• Temperature range: 0°C to 90°C
• Fahrenheit range: 32°F to 194°F
• Sensing method: Liquid-expansion capillary bulb
• Contact configuration: SPDT
• Contact terminals: COM, normally open (NO) and normally closed (NC)
• Durvela control connection: COM to NO
• Control action: COM-to-NO closes on temperature rise in the Durvela wiring configuration
• System voltage: 12 VDC
• Controlled load: Durvela 12 VDC, 6 W brushless aeration fan
• Normal fan current: Approximately 0.5 A
• Adjustment method: Manual temperature-control dial
• Electrical power required for sensing: None
• Installation location: Inside the solar aeration fan enclosure
• Fan negative connection: Direct common-negative return; not switched by the thermostat
• Intended service: Low-voltage temperature-controlled ventilation

1. Move the source selector to OFF.
2. Unplug the DC backup adapter.
3. Disconnect or completely cover the solar panel.
4. Photograph and label the existing thermostat connections before removing any wires.
5. Mount the replacement thermostat in the original enclosure location using the supplied mounting hardware.
6. Route the capillary tube carefully without kinking, crushing, cutting or sharply bending it (wet hose with a mild detergent in water to help lubricate it if the bulb is difficult to insert) .
7. Position the sensing bulb in the original sensing location or thermowell, if fitted. 
8. Connect the selector’s COMMON output wire to the thermostat COM terminal.
9. Connect the thermostat NO terminal to the fan-positive wire.
10. Leave the NC terminal unused and individually insulated.
11. Keep the fan, solar-panel and DC-adapter negatives connected to the separate common-negative return.
12. Reinstall all enclosure covers, gaskets and seals before restoring power.
13. Test operation using both the SOLAR and ADAPTER selector positions.

Turn the temperature dial toward a higher setting to delay fan operation. Turn it toward a lower setting to make the fan operate at a lower sensed temperature.

• Durvela Adjustable Capillary Thermostat Replacement Instructions
• Durvela Solar Aeration Repair Help Guide
• Durvela Adjustable Capillary Thermostat Specification Sheet

• Disconnect both the solar panel and DC adapter before opening the enclosure or servicing the thermostat.
• The thermostat is a dry-contact mechanical switch; it does not generate or regulate the 12 VDC supply.
• The Durvela system uses the COM and NO contacts so the fan turns on as temperature rises.
• The NC terminal is not used and must remain individually insulated.
• Do not route the negative return through the thermostat.
• Never cut, puncture, crush or tightly bend the capillary tube or sensing bulb. The capillary system is sealed and cannot be repaired if damaged.
• Avoid placing the capillary tube against sharp edges, hot surfaces or moving components.
• Temperature markings are approximate. Mechanical thermostats normally have operating tolerance and switching differential.
• Test the fan at the intended temperature setting before returning the system to service.
• Use only with the Durvela low-voltage fan circuit unless the thermostat’s contact rating has been independently confirmed for another load.
• Do not connect this thermostat directly to AC mains voltage.