What Is a Heating Thermostat? Operating Principle and Selection Criteria
A heating thermostat switches on the panel heater through its NC contact when the panel temperature falls below the setpoint and stops it as the temperature rises.
A heating thermostat is a thermostat with an NC (normally closed) contact that keeps its contact closed and runs the panel heater while the temperature inside the panel is below the setpoint, then opens the contact and stops the heater when the setpoint is reached. In outdoor panels, cold stores and unheated buildings it prevents condensation and freezing and so protects drives, PLCs and relays.
How does it work?
In a KTO 011 type mechanical thermostat, a bimetal element changes shape with temperature and opens or closes the contact; no supply is needed. After the contact opens, the temperature has to fall a few degrees before it closes again. This difference (hysteresis) stops the heater from switching on and off constantly. An electronic thermostat measures temperature with a sensor, switches the heater with an output relay and needs a supply voltage.
Heating thermostat types in the catalogue
| Type | Example in the catalogue | When to choose it |
|---|---|---|
| Mechanical NC thermostat | KTO 011 type (Gwest, Isıso, KSN), Schneider Electric NSYCCOTHC | Heater control by temperature only |
| Dual thermostat (NC + NO) | Schneider Electric NSYCCOTHD | Heater and fan from one device |
| Electronic thermostat | Schneider Electric NSYCCOTH230VID | When temperature should be measured by an electronic sensor |
| Hygrostat (humidity meter) | Schneider Electric NSYCCOHY230VID | Places where humidity rises without a temperature change |
| Hygrotherm (temperature and humidity) | Schneider Electric NSYCCOHYT230VID | One device against freezing and condensation |
Mechanical heating thermostats are identified by their red housing; the KTO 011 type and NSYCCOTHC are red. Blue-housed models with an NO contact are cooling thermostats used in fan circuits.
Selection and setting criteria
- Setpoint: KTO 011 type thermostats are adjustable from 0 to 60 °C. Set it above the lowest operating temperature of the devices in the panel. If the same panel has a cooling thermostat, the heating setpoint must stay below its setpoint; otherwise the heater and fan run at the same time.
- Contact current: If the thermostat switches the heater directly, the heater current must not exceed the contact rating; for example, a 400 W heater at 230 V draws about 1.7 A. PTC heaters briefly draw more current when cold, so leave a margin on the contact rating. If the current exceeds the contact, the thermostat drives a contactor or relay.
- Position: Fit the heater in the lower part of the panel and the thermostat at a point away from the heater and from heat-producing devices. A thermostat directly above the heater switches it off before the panel has warmed up.
- Humidity: Condensation forms when relative humidity rises and the surface temperature drops to the dew point; while the temperature is above the setpoint, the thermostat does not see this. In coastal areas, wash-down areas and cold stores, use a hygrostat next to the thermostat or a hygrotherm in one device.
- Supply: Mechanical thermostats need no supply. The Schneider Electric electronic thermostat and hygrotherm in the catalogue run on 220–240 V AC, the humidity meter on 110–240 V AC.
Common mistakes
- Connecting the heater to an NO cooling thermostat: The heater runs when the panel warms up and stops in the cold.
- Running the heater without a thermostat: The heater draws power continuously and heats the panel unnecessarily.
Heating thermostats in the Welibaba catalogue
The Heating Thermostats category has 8 active products:
- KTO 011 type NC thermostat (3): Gwest 6682, Isıso KTO-011 and KSN6051; the price is shown on the product page and they can be added to the cart.
- Schneider Electric (5): NSYCCOTHC NC thermostat, NSYCCOTHD dual thermostat, NSYCCOTH230VID electronic thermostat, NSYCCOHY230VID humidity meter and NSYCCOHYT230VID temperature and humidity meter. These products are supplied on a lead-time basis; for price and lead time, use the product advisor, WhatsApp or email option on the product page.
Heaters to connect to the thermostat are in the Panel Heaters category, and thermostats for fan circuits in the Cooling Thermostats category. For a side-by-side comparison of heating and cooling thermostats, see the Panel Thermostats page.
Frequently asked questions
What temperature should a heating thermostat be set to?
There is no single value. Set it above the lowest operating temperature of the devices in the panel and, if there is a cooling thermostat, below its setpoint; add a hygrostat against humidity-driven condensation.
What contact type does a KTO 011 thermostat have?
NC: below the setpoint the contact is closed and the heater runs; when the setpoint is reached it opens. Its NO counterpart used for fans is the KTS 011.
Can a hygrostat replace a heating thermostat?
A hygrostat monitors humidity only; a panel at risk of freezing also needs temperature control. Use both together or a hygrotherm that combines them in one housing.