KSD thermostats (also known as Klixon Safety Devices or bimetallic disc thermostats) are commonly used in electric water heaters due to their reliability, safety features, and cost-effectiveness. Here's why they are widely preferred:
1. Over-Temperature Protection (Safety)
KSD thermostats act as fail-safe devices that cut off power if the water temperature exceeds a set limit (typically around 90–95°C).
This prevents boiling, excessive pressure buildup, and tank damage, reducing the risk of scalding or tank rupture.
2. Manual Reset vs. Auto Reset Options
Some KSD thermostats feature a manual reset function, requiring user intervention after tripping, ensuring the issue is checked before reuse.
Others are auto-reset, but they still provide critical thermal cutoff protection.
3. Simple & Durable Design
They use a bimetallic disc that snaps open/closed at a specific temperature, requiring no external power.
No complex electronics mean long lifespan and resistance to electrical noise.
4. Compliance with Safety Standards
Many electric water heaters must meet UL, CE, or IEC safety standards, and KSD thermostats are certified for such applications.
5. Cost-Effectiveness
Compared to electronic controllers, KSD thermostats are cheaper while still providing essential protection.
6. Redundancy with Primary Thermostat
Most water heaters have a primary adjustable thermostat for regular temperature control.
The KSD serves as a secondary backup in case the primary thermostat fails (e.g., contacts welding shut).
Common KSD Models in Water Heaters
KSD301 (fixed temperature, auto-reset)
KSD302 (manual reset, higher safety)
KSD305 (adjustable trip point)
Where Are They Installed?
Typically mounted on the tank's surface or near heating elements to detect overheating quickly.
