A solid state relay switches AC power with semiconductors instead of contacts. There is nothing to arc, nothing to wear and nothing to make a noise — which is why SSRs have taken over almost all temperature control duty from mechanical contactors.
Why heaters need solid state switching
Temperature control means switching frequently. A PID controller driving a heater may cycle the output every few seconds, which for a mechanical contactor means millions of operations in a year — far beyond its rated contact life. Contacts erode, then weld, and the heater fails on or the process fails cold.
A solid state relay has no contacts. It switches at the zero crossing of the AC waveform, so there is no inrush arc, no contact erosion and no electrical noise injected into the panel. Life is measured in semiconductor terms, not mechanical cycles.
SSRs generate heat in proportion to load current — roughly one watt per amp. Always mount on an adequately sized heatsink with thermal compound, and allow free air movement. Overheating is the single most common cause of SSR failure.
Key features
- No moving parts — no contact wear, no welding, no mechanical failure mode.
- Silent operation — no clatter in the panel, valuable in labs and clean areas.
- Zero-crossing switching minimises inrush current and electrical noise.
- Very high cycling life suited to PID temperature control.
- Low control power — driven directly from a controller output.
- Fast switching for tight temperature regulation.
Technical specifications
| Parameter | Value |
|---|---|
| Type | Single phase solid state relay |
| Load | Single phase AC — resistive heating loads |
| Switching | Zero-crossing |
| Control input | DC control signal from controller or PLC |
| Mounting | Panel mount on heatsink |
| Cooling | Heatsink required, sized to load current |
| Status indication | LED |
Typical applications
- Electric heater control on ovens, furnaces and extruders.
- PID temperature loops in plastics, packaging and food processing.
- Any resistive load requiring frequent switching.
- Replacing contactors that are failing prematurely from high cycle counts.
How to order
Tell us the sensing gap, the target material, your supply voltage and the output type your controller needs. If you are replacing an existing sensor, a photograph of the body markings is usually enough for us to identify an equivalent. We will confirm the specification and quote — normally the same day.
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Frequently asked questions
What size heatsink do I need?
Size it against load current — an SSR dissipates roughly one watt per amp of load. Tell us your heater current and panel ambient temperature and we will recommend a heatsink. Under-sizing it is the most common reason SSRs fail early.
Can an SSR switch a motor?
Standard SSRs are specified for resistive loads. Motors are inductive and draw a large starting current, so they need an SSR specifically rated for motor duty and generously de-rated. Tell us the motor rating and we will advise.
Does an SSR provide isolation?
The control input is optically isolated from the load circuit. However, an SSR fails short more often than open, so it does not provide safe isolation. Always fit a mechanical means of isolation for maintenance.
Need a quote for the Single Phase Solid State Relay?
Send us your application — target material, sensing distance, supply voltage and housing constraint. We will recommend a part, quote it, and ship from Mumbai.