Instructions for Electricians

The function of the fan controller is to turn the fans on when the air is cold enough to cool the grain, turn them off when the air gets too warm, and record the hours of fan operation.

Components:

• A common thermostat: The Honeywell T6031A1136 (Grainger #2E834) and the Sunne TRF115 (Grainger #4MY93) are appropriate.¹
• An hour meter
• Contacts, Relays, Delays (if the fans don’t have them)
• A main control that provides the options “manual-off-auto”

Thermostat:

• Must be easy to read. The operator will have to re-set the thermostat every year.
• Must have a wide differential. The difference between the “activate” and the “de-activate” temperature should be 3ºF to 5ºF to avoid frequent on-off cycles when the air temperature remains for long periods of time near the set-point temperature.
• Must have a temperature sensor that can be located outside the enclosure. The fans must respond to the ambient temperature, not the temperature inside a control box or an electrical room.
• Must operate as a high-limit switch to eliminate fan operation when the air is too warm. It must be wired or set to operate as though it were controlling a home furnace, not an air conditioner. It must NOT be set to “cool”.
• Locate the temperature sensor out of sun and rain, but not inside an enclosure or in contact with metal or concrete walls. The sensor must sense the outside air temperature without undue interference from heat stored in walls, floors, or roofs.

Electrical Box:
Must be easy to open without tools. The operator must check the hour meter often, and must re-set the thermostat every season.

Delays:
If multiple, large fans are controlled, they must not be activated at the same time. A 30-second delay is long enough to avoid the peak demand issue.

Hour Meter:
A reset function is helpful, but not required.

Extraction Fans:
If the bin has extraction fans on the roof, they must activate whenever the aeration fans start.