Series-DFS2

Supported Applications

The Series DFS2 Low Limit Freeze Protection Switch protects the cooling coils in air handler systems by preventing frost build-up. Its capillary sensing element provides an antifreeze function by sensing the lowest temperature along any one-foot section of capillary, so a localized cold spot along the coil face triggers a response even if the average temperature is higher.

The switch integrates into building management systems: its DPDT relays signal the building management system while also cutting off the fan when the sensed temperature drops below the set point. Automatic and manual reset options let the switch be matched to installations that either recover on their own or require a deliberate operator reset after a freeze event.

Operating Conditions & Performance

The switch operates over a process temperature range of 14°F to 54°F (-10°C to 12°C) with a fixed hysteresis of 1.8°F. The low-level set point is factory set at 39°F (4°C) with the safety lock secured, and is adjustable through a screwdriver slot.

Ambient and storage temperatures both span 14°F to 158°F (-10°C to 70°C), and the humidity limit is 0 to 95% RH, non-condensing. The vapor-filled copper capillary tolerates a capillary overload temperature of 392°F (200°C) for a maximum of 60 minutes.

The enclosure uses a galvanized steel base with an ABS cover and carries a NEMA 1 (IP40) rating; the product is CE marked. The electrical rating is 24 to 250 VAC, 15 (8) A, and the output consists of two sets of NO/NC/Common contacts. Field wiring lands on terminals with wire-retaining screws sized for a maximum of 14 AWG, and cable entry is provided through one M20 compression fitting. Each unit weighs 1.6 lb (0.7 kg).

Configuration Options

All four models share the same vapor-filled copper capillary sensing element, DPDT contact arrangement, 14°F to 54°F (-10°C to 12°C) operating range, and NEMA 1 (IP40) enclosure. They differ in two respects: reset action and capillary length.

The DFS2-DA models and DFS2-DM models provide the two reset actions, automatic and manual, so the switch can be specified to either recover automatically once the freeze condition clears or hold until manually reset. The trailing digits, 10 and 20, denote the two capillary length options, allowing the sensing length to be matched to the coil face being protected.

Key Product Differences

The series consists of four models:

• DFS2-DA10
• DFS2-DA20
• DFS2-DM10
• DFS2-DM20

An optional accessory is available:

• A-DFS2-C — capillary mounting clips (6 pieces)