Omron K8AK-TS1 100-240VAC — PTC Motor Thermistor Relay
SKU: K8AK-TS1 100-240VACUSD 27.00
K8AK-TS PTC thermistor motor protection relay, trip ~3100 Ω, SPDT 5 A output, 22.5 mm DIN-rail, 100-240 VAC.
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Product Overview
The Omron K8AK-TS1 100-240VAC is a thermistor motor protection relay from the K8AK-TS / PT family. It sits on a DIN rail next to the motor contactor, watches a PTC (positive temperature coefficient) thermistor that is embedded in the motor windings, and trips a single SPDT output when the winding temperature rises past the trip level. The trip threshold is fixed by the PTC curve: the relay operates at about 3100 Ω, resets at about 1650 Ω, and also flags a thermistor short (0–10 Ω) or open circuit.
Where the K8AK-TS1 sits in the cabinet
Wire the PTC thermistor leads to terminals T1 / T2 on the relay, and the SPDT output to the motor contactor coil, a PLC input, or an alarm beacon. When the motor overheats (locked rotor, single phasing, blocked ventilation, excessive load), the PTC resistance rises sharply and the relay drops the contactor. This is a different protection than a thermal overload relay, which only senses current — a PTC relay catches a stalled blower or a slow-rising blockage that the overload relay might miss.
TS1 vs PT1 within the K8AK-TS / PT family
The K8AK-TS1 (this SKU) only monitors temperature. The K8AK-PT1 100-240VAC adds phase-sequence and phase-loss detection on top — three-phase monitor plus PTC, in the same 22.5 mm wide body. If the motor is three-phase and you want phase protection from one relay, pick the PT1. If the motor is single-phase or you already have a separate phase monitor, the TS1 is the lower-cost option. Both share the same TEST/RESET button, the same auto / manual reset dip switch, and the same DIP-switched trip behaviour.
Before ordering
Confirm the supply is in the 100-240 VAC range; for 24 VDC-fed cabinets, order the K8AK-TS1 24VAC/DC instead. Use a PTC thermistor that follows the DIN 44081 / IEC 60947-8 standard (most motor manufacturers embed these as standard). For a wider DIN-rail cabinet of monitoring relays, the K8DS-PU2 (three-phase voltage) and K8AK-AS1 (single-phase current) share the same 22.5 mm body and slot in side by side.
Key Features
- K8AK-TS PTC thermistor motor protection relay
- PTC trip ≈3100 Ω; reset ≈1650 Ω (DIN 44081 / IEC 60947-8)
- Thermistor open and short detection (0–10 Ω)
- SPDT output, 5 A at 250 VAC / 30 VDC resistive (1250 VA / 150 W)
- Operating time ≤0.2 s on PTC trip
- Manual reset via TEST/RESET button; auto / manual selectable on front
- 22.5 mm wide DIN-rail body, 90 x 100 mm
- 100-240 VAC supply, 3.5 VA max
- Operating temperature -20 to +60 °C
- SKU: K8AK-TS1 100-240VAC
- Series: K8AK-TS / PT thermistor motor protection relay
- Voltage: 100-240 VAC
- I/O: 5 I/O
Best-Fit Applications
- Winding over-temperature protection on a pump or fan motor where a thermal overload alone is not enough
- Stator overtemperature trip on a small inverter-fed motor where the drive alone cannot detect heat rise
- Backup protection on a critical motor alongside a thermal overload relay and the K8AK-PT1 phase monitor
- Single-phase motor protection in a cabinet that already has its own phase-loss detection upstream
- PTC monitoring for a heater band, transformer, or bearing-temperature sensor that follows DIN 44081
Buying Checklist
- Pick K8AK-TS1 for temperature-only protection — pick K8AK-PT1 if you also need phase-sequence and phase-loss from one relay.
- Confirm the supply is 100-240 VAC; for a 24 V cabinet, order the K8AK-TS1 24VAC/DC version instead.
- Use motors with embedded PTC thermistors that follow DIN 44081 / IEC 60947-8 — most name-brand motors ship with these.
- Plan a 22.5 mm-wide DIN-rail slot — the K8AK-TS1 slots next to K8AK-AS1 and K8DS-PU2 relays for compact panels.
- Use the manual reset (TEST/RESET button) during commissioning to confirm the output contacts drop on PTC trip.
Technical Specifications
| Model | K8AK-TS1 100-240VAC |
|---|---|
| Series | K8AK-TS / PT thermistor motor protection relay |
| Monitoring | PTC thermistor temperature (TS suffix) |
| PTC Trip / Reset | Trip ≈3100 Ω; reset ≈1650 Ω (DIN 44081 / IEC 60947-8) |
| Short-Circuit Detection | 0–10 Ω (±5 Ω) |
| Output | SPDT relay, 5 A at 250 VAC / 30 VDC resistive (1250 VA / 150 W max) |
| Operating Time | ≤0.2 s on PTC trip |
| Reset | Manual (TEST/RESET button) or auto (DIP switch) |
| Power Supply | 100-240 VAC 50/60 Hz, 3.5 VA max |
| Dimensions (W × H × D) | 22.5 × 90 × 100 mm |
| Operating Temperature | -20 to +60 °C |
| Approvals | UL 508, CSA C22.2 No.14, EN 60947-5-1, CCC |
Resources & Downloads
FAQ for K8AK-TS1 100-240VAC
What is the difference between K8AK-TS1 and K8AK-PT1?
K8AK-TS1 (this SKU) only monitors the PTC thermistor for temperature. K8AK-PT1 adds three-phase voltage monitoring on top — phase-sequence error and phase-loss detection in the same 22.5 mm-wide body. Pick TS1 when the motor is single-phase or you already have a separate phase monitor; pick PT1 when the motor is three-phase and you want both functions in one relay.
What kind of PTC thermistor does the K8AK-TS1 need?
Any PTC that follows DIN 44081 / IEC 60947-8. These are the standard motor-protection PTCs with a rated trip temperature chosen by the motor manufacturer (typically 130, 145, or 155 °C for insulation class B / F). The relay evaluates the thermistor resistance — it does not need a specific trip-temperature setting. Three PTCs are typically wired in series inside the motor.
Can the K8AK-TS1 detect a broken thermistor wire?
Yes. An open circuit (very high resistance) is flagged as a fault and the output drops the same way as an overtemperature. A short circuit (0–10 Ω across the two PTC terminals) is also detected and flagged. This means a broken or shorted thermistor lead does not leave the motor unprotected — the relay treats it as a trip condition.
Does the K8AK-TS1 need a separate power supply?
Yes — this SKU runs on 100-240 VAC 50/60 Hz and consumes up to 3.5 VA. If the cabinet is 24 VDC-fed, order the K8AK-TS1 24VAC/DC variant instead. Power consumption on the 24 V variant is about 1.8 VA at AC and 1.0 W at DC.
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