I. Product Overview
The KSD309 series thermostat is a bimetallic strip temperature controller with a fully enclosed housing, designed specifically for high-power devices such as electric water heaters. Utilizing the principle of thermal expansion and contraction of a bimetallic strip, when the preset temperature is reached, the disc-shaped element momentarily jumps, causing the contacts to actuate rapidly through a mechanism, thus connecting or disconnecting the circuit and providing safety protection for the appliance.
This model is a manual reset type. When the temperature exceeds the limit and the circuit is disconnected, the reset button must be pressed manually to restore the circuit conduction. It is especially suitable for overheat protection and anti-dry burning protection of products such as electric water heaters, electric heating equipment, and boilers.
II. Product Features and Advantages
- Designed specifically for high-power loads: Optimized for high-power applications such as electric water heaters, the contact system has excellent current-carrying capacity.
- Three-pole single-throw (3PST) contact structure: It adopts a three-pole single-throw (3PST) contact design, which can simultaneously control the on/off of three circuits, and is suitable for application scenarios that require simultaneous switching of multiple loads.
- Rapid disconnection technology: A temperature-sensitive bimetallic strip is used to achieve rapid contact action (sudden snap action) to ensure that the circuit can be quickly cut off when the temperature exceeds the limit.
- High reliability and long lifespan: The speed and force of contact separation are optimized to effectively reduce arc erosion and ensure that the controller has a long and reliable lifespan even under high load conditions.
- Fully enclosed insulated housing: Made of bakelite (phenolic resin), providing excellent electrical insulation and protection.
- Manual reset safety mechanism: Manual intervention is required to reset the device after troubleshooting to prevent it from restarting automatically without supervision and improve safety.
III. Application
- Instantaneous electric water heaters and storage electric water heaters
- Electric heating equipment, electric welding machine
- Steam heaters, boilers
- High-power mechanical equipment and electrical products
IV. Main Technical Parameters
| Parameter Items | Specifications |
| Model | KSD309 |
| Contact structure | Three-Pole Single-Throw (3PST) |
| Reset method | Manual reset |
| Shell material | Bakelite (phenolic resin) |
| Rated electrical parameters | AC 400V / 35A, 45A, 63A |
| Operating temperature range | 50℃ ~ 150℃ (customizable) |
| Operating temperature tolerance | ±3℃ ~ ±5℃ |
| Contact resistance | ≤50mΩ |
| Insulation resistance | ≥100MΩ |
| Electrical strength | 1500V~/5mA/1min |
| Service life | Manual cycle life: ≥3,000 cycles |
| Wiring method | M4 screw fixing method |
| Certification | CQC (CQC19002223566) |
V. Installation Method
Installation method: Use contact temperature sensing installation, ensuring the metal cover is in close contact with the mounting surface of the controlled appliance. To ensure effective temperature sensing, it is recommended to apply thermal grease to the sensing surface.
Precautions:
- Do not deform or collapse the cover during installation, as this may affect performance.
- To prevent electrical leakage, avoid liquid from seeping into the thermostat and ensure that the casing is free of cracks.
- Please connect the wires correctly according to the markings on the casing.
