Omron K8AK-AS1 24VAC-DC — Current Monitoring Relay, 2-500 mA
SKU: K8AK-AS1 24VAC-DCUSD 58.00
K8AK single-phase current monitoring relay, 2-500 mA over three DIP-switched ranges, SPDT 5 A output, DIN-rail, 24 VAC/DC supply.
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Product Overview
The Omron K8AK-AS1 24VAC-DC is a single-phase current monitoring relay from the K8AK series of DIN-rail monitoring relays. The "AS" suffix means current monitoring (overcurrent or undercurrent, selectable on the front panel); the "AW" suffix covers undercurrent + overcurrent in one unit. The "1" in K8AK-AS1 picks the low-current sub-family, with three DIP-switched current ranges from 2 mA to 500 mA. This SKU runs on 24 VAC/DC, which fits neatly next to other 24 V control gear in a cabinet.
Where the K8AK-AS1 earns its keep
Use a K8AK-AS1 to watch a low-current load and trip when the current goes too high (overcurrent) or falls too low (undercurrent). Typical uses include heater-band open detection, signal-lamp burnout detection, small-pump dry-run detection (via the undercurrent side), and conveyor current-stall detection on a sub-amp drive. The adjustable operating time and start-up lock let you suppress nuisance trips at machine start, where inrush current is normal. For 1 A through 8 A loads, step up to the K8AK-AS2; for 10 A through 200 A with a current transformer, use the K8AK-AS3.
Setting up the relay
Setup is via four front-panel elements: a current-range DIP switch (I1 / I2 / I3), an operating-value knob (10-100% of the chosen range), a hysteresis knob (5-50% of the setpoint), and an operating-time knob (0.1-30 s). The start-up lock (0-30 s) deliberately ignores overcurrent during the first seconds of machine start. Output is a single SPDT contact rated 5 A at 250 VAC, wired to a contactor, alarm lamp, or PLC input. Manual reset vs auto reset is a front-panel switch.
Before ordering
Plan a 22.5 mm wide slot on the DIN rail — K8 series relays slot in neatly next to each other and next to K8DS series monitoring relays. Power consumption is about 2 VA / 1.1 W at 24 V. For a higher-current load, pick a K8AK-AS2 (up to 8 A direct) or K8AK-AS3 (10-200 A with the K8AC-CT200L current transformer). For phase-loss and phase-sequence protection of a three-phase motor, use the K8DS-PM or K8DS-PH series instead.
Key Features
- K8AK series single-phase current monitoring relay
- Overcurrent or undercurrent selectable on the front panel
- Three input ranges via DIP switches: 2-20 mA / 10-100 mA / 50-500 mA
- Operating-value knob 10-100% of the chosen range
- Operating time 0.1-30 s; start-up lock 0-30 s (overcurrent only)
- SPDT output, 5 A at 250 VAC
- Manual reset or auto reset — front-panel switch
- DIN-rail mount, 22.5 x 100 x 95 mm
- 24 VAC/DC supply; K8AK-AS1 100-240 VAC variants also exist
- SKU: K8AK-AS1 24VAC-DC
- Series: K8AK single-phase current monitoring relay
- Voltage: 24 VAC
- I/O: 1 I/O
Best-Fit Applications
- Heater-band open detection or signal-lamp burnout detection in a sub-amp control loop
- Dry-run protection on a small pump where a falling current under-load signals an empty tank
- Conveyor motor-stall detection on a sub-amp gearmotor (current rises when the belt jams)
- Light-load process alarming on a small mixer or stirrer where the in-process current should sit in a band
- PLC-side current limit check on a small packaging machine's vacuum or solenoid circuit
Buying Checklist
- Choose K8AK-AS1 for a low-current (2-500 mA) single-phase current monitor; step up to K8AK-AS2 for 1-8 A direct, or K8AK-AS3 for 10-200 A with a CT.
- Use the start-up lock (0-30 s) to ignore the inrush at machine start, especially on motor loads with capacitor banks or heater bands.
- Pick the K8AK-AW1 if you need both overcurrent and undercurrent tripping from one unit; the K8AK-AS trips on one direction only.
- Plan DIN-rail space — the K8AK is 22.5 mm wide and 95 mm deep, and slots in next to K8DS phase monitors and other 22.5 mm-wide K8-series relays.
- Verify the 24 VAC/DC supply is available in the cabinet; for 100-240 VAC, order the K8AK-AS1 100-240VAC SKU instead.
Technical Specifications
| Model | K8AK-AS1 24VAC-DC |
|---|---|
| Series | K8AK single-phase current monitoring relay |
| Monitoring Function | Overcurrent or undercurrent (front-panel switch) |
| Input Range (DIP-switched) | I1: 2-20 mA (~5 Ω) / I2: 10-100 mA (~1 Ω) / I3: 50-500 mA (~0.2 Ω) |
| Setpoint / Hysteresis | 10-100% of full-scale; hysteresis 5-50% of setpoint |
| Operating Time | 0.1 to 30 s adjustable |
| Start-Up Lock Time | 0 to 30 s (overcurrent only) |
| Reset | Manual or auto reset (front-panel switch) |
| Output | SPDT (1 Form C), 5 A at 250 VAC |
| Power Supply | 24 VAC/DC (this SKU); 100-240 VAC variants also exist |
| Mounting / Size | DIN-rail, 22.5 (W) x 100 (H) x 95 (D) mm |
| Approvals | UL, CSA, CE, CCC |
Resources & Downloads
FAQ for K8AK-AS1 24VAC-DC
What is the difference between K8AK-AS1 and K8AK-AW1?
K8AK-AS1 monitors for either overcurrent OR undercurrent — the direction is set on the front-panel switch. K8AK-AW1 monitors for both overcurrent AND undercurrent at the same time, with separate setpoints. Pick AS when you only need a single-direction trip; pick AW when you need to detect both an upper and a lower bound on the load current.
How does the K8AK-AS1 measure current?
Direct input — the load current passes through the relay's input terminals (I1 / I2 / I3 depending on range). For low-current ranges, the internal impedance is high enough that no shunt or CT is required. For higher currents, the K8AK-AS2 handles 1-8 A direct, and the K8AK-AS3 takes a current-transformer signal (10-100 A or 20-200 A with the K8AC-CT200L CT).
What supply voltage does the K8AK-AS1 need?
This SKU runs on 24 VAC/DC (the "24VAC-DC" suffix in the part number). If your cabinet supply is 100-240 VAC, order the K8AK-AS1 100-240VAC variant instead. Power draw is around 2 VA at 24 V and 4.6 VA at 100-240 V.
Can the K8AK-AS1 ignore inrush current at start-up?
Yes. The start-up lock timer (0-30 s) is set on the front panel and ignores overcurrent for that many seconds after power-on. After the lock expires, normal monitoring resumes. This is useful for heater-band or motor loads where the inrush is much higher than the steady-state current.
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