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Thermal Protector F09

Power class: 4,0 A to 25,0 A
Type series: 09

  • normally open
  • resets automatically
  • with connector cables
  • fully insulated in a Nomex® cap
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Thermal Protector F09
Thermal Protector F09
Thermal Protector F09
Thermal Protector F09

Switchgear consisting of a movable silver contact (1), a contact bearer (2), a spring snap-in disc (3) and a bimetallic disc (4) which is riveted into one another, undetachable and fixed in a positive lock and self-aligning between a conductive, heat-transferring housing (5) and a contact cap made of steel (6) that is insulated from it, plus a stationary countercontact (7). At the same time, the switchgear is held open by the spring snap-in disc (3) used as a transfer element for electric current which is held between a supporting collar and a circumferential ring. As such, the bimetallic disc (4) underlying it, that is also stuck out from the movable contact (1), can continuously work (exposed) by mechanical loads. As soon as the bimetallic disc (4) reaches its rated switching temperature, it effectively springs against the throw force of the spring snap-in disc (3) into its inverted position. The contact is abruptly closed. The spring snap-in disc (3) is now a transfer element for electric current and as such, it enables the bimetallic disc (5) to continue to work on a continuous basis. When the spring back temperature is reached, the bimetallic disc snaps back into its start position and the contact is opened again.

Technical specifications

Nominal switching temperature (NST) in 5°C
50 °C - 180 °C
Tolerance (standard)
±5 K
Reverse switch temperature (RST)
≥ 30° C (≤ 75° C NST)
-30 K ± 15 K (≥ 80° C ≤ 180° C NST)
≥ 35 °C
(defined reset temperature possible on customer request)
Installation height from
6.5 mm
11.4 mm
Resistance to impregnation
Suitable for installation in protection class
Pressure resistance to the switch housing
300 N
Standard connection
Lead wire 0.5 mm² / AWG20
Operating voltage range AC
up until 500 V AC
Rated voltage AC
250 V (VDE) 277 V (UL)
Rated current AC cos ϕ = 1.0 / cycles
6.3 A / 10,000
Rated current AC cos ϕ = 0.6 / cycles
4.0 A / 10,000
High voltage resistance
2.0 kV
Total bounce time
< 1 ms
Contact resistance (according to MIL-STD. R5757)
≤ 50 mΩ
Vibration resistance at 10 ... 60 Hz
100 m/s²


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