Duty temperature decides the construction before anything else does. At 120 °c to 150 °c, ksd9700 bimetal thermostats is a candidate; the sections below set out what it will hold, what has to be true for it to hold it, and what fails first when it does not.
What the 120 °C to 150 °C Band Requires
Process and platen heating, adhesive curing, epoxy-encapsulated plates at their limit. Silicone and polyimide are comfortable here; the encapsulant, not the element, is usually what constrains the design.
| Band | 120 °C to 150 °C |
|---|---|
| This construction, continuous | 150 °C |
This band reaches the ceiling of the construction. At 150 °C there is no headroom left, so the control has to hold the set point rather than approach it from above, and the limit device has to be set where it can act before the insulation does. A duty that spends its time at the top of the band is a duty that should be quoted against the next construction up.
Why the Boundary Is Where It Is
150 °C is the ceiling of filled epoxy, and on an encapsulated plate the encapsulant fails before either the element or the plate is troubled. It is also roughly where acrylic pressure-sensitive adhesives give up, which matters on any heater that is held on by its own adhesive rather than clamped.
Silicone and polyimide are comfortable through this band with 50 °C of margin in hand; the constraint is usually the bonding system, not the heater.
What a KSD9700 Bimetal Thermostats Is
The small snap-action bimetal disc fitted inside most of the heaters in this catalog: it opens at a fixed temperature and closes again when the part has cooled.
A bimetal disc that opens a contact at a fixed temperature. It is not an accurate controller and is not meant to be one: it is the device that decides whether the heater around it survives a fault, and it is specified by its open temperature, its reset behaviour and the current it can break.
The heat leaves through whatever the component is clamped or bonded to; a sensing component adds no heat of its own and simply has to be in thermal contact with the thing it is reporting on.
| Total thickness | Component |
|---|---|
| Maximum size, one piece | Component |
| Continuous working temperature | 150 °C |
The continuous limit of 150 °C is set by the insulation system. The element alloy would run far hotter; it is never the element that decides.
Which Temperature Is Being Held
Three temperatures matter and they are not the same number: the element temperature, the temperature of the surface being heated, and the ambient. A heater rated for a continuous working temperature is rated at the element — the hottest point in the assembly, and the one nothing on the outside is measuring.
The gap between element and surface is the thermal path. Bonded to metal it may be a few degrees; across an air gap, a void in the adhesive or a dry clamped joint it can be tens of degrees, and every one of them appears at the element rather than at the load.
Control and Protection
This heater has no way of limiting its own temperature. Resistance heating draws roughly the same power whatever the temperature, so with the load removed, the fluid gone, the fan stopped or the sensor open circuit, the element keeps producing watts until something stops it.
The design must therefore contain a control device and, separately, a protective one: a controller with a sensor to hold the set point, and a bimetal thermostat or a one-shot thermal cutoff wired in series with the element to open the circuit if the loop ever fails. The two are not interchangeable — a controller that has lost its sensor cannot protect anything, which is exactly the fault the cutoff exists for.
Where This Construction Is the Wrong Answer
- Do not plan on running above 150 °C. That ceiling belongs to the insulation system, not to the element alloy, and it is not a figure that derating extends — past it the insulation degrades and the dielectric strength goes with it.
- Do not rate this component as though it were the heater. It carries a contact rating or a tolerance class; the heater next to it decides the power, the watt density and the temperature the assembly reaches.
Other Constructions That Hold 120 °C to 150 °C
Constructions in this catalogue that will hold 120 °c to 150 °c continuously:
How to Specify One
This is a made-to-drawing part, so there is no catalogue number to quote. A quotation is built from the following, and the more of it that arrives with the enquiry the fewer rounds it takes:
- The temperature to be sensed or switched, and the tolerance the application actually needs.
- Where the component sits — against the element, in the potting, on the load, or in the airflow.
- The electrical duty: for a switching device, the voltage, the current and whether the load is AC or DC.
- Lead length, insulation and termination, and whether the component is fitted by us into a heater assembly or supplied loose.
- The standard the end product is certified to, so the component chosen is one that fits inside that approval.
Lead time: Samples 7-10 days from approved drawing; production 15-20 days.
KSD9700 Bimetal Thermostats — Capability Table
These are process limits for the construction, not the specification of one stocked item. Every line is what the factory can hold; what your part holds is fixed on your drawing.
| Parameter | Specification | Limit / note |
|---|---|---|
| Type | Snap-action bimetal disc, normally closed or normally open | Normally closed is the protective configuration |
| Open temperature | +40 u00b0C to +150 u00b0C in 5 u00b0C steps | Fixed at manufacture u2014 it is not adjustable |
| Tolerance | u00b15 u00b0C standard, u00b13 u00b0C selected | On the open point, measured rising |
| Reset differential | 15 u00b0C to 25 u00b0C below the open point | Wide differential is deliberate: it stops the contact chattering |
| Switching rating | 5 A at 250 V AC resistive | Resistive only u2014 a heater is a resistive load, which is why this rating applies |
| Life | 10,000 cycles at rated load | Far more at a fraction of the rating |
| Mounting | Vulcanised inside the heater, bonded to the plate, or bolted | It must read the part it is protecting, not the air near it |
| Certifications | UL, VDE, CQC on the component | Component approval carries into the heater assembly file |
Figures are the published tolerance and rating bands of the standard sensor and control components fitted to these heaters. Sensor tolerance classes follow IEC 60751 for RTDs and IEC 60584 for thermocouples; thermostat and thermal cutoff ratings are the component manufacturers' own.
