HERZ thermostatic head with remote sensor 40-70°C, M28x1.5, 1742100

HERZ 1742100 / 1 7421 00 is a thermostat with a contact temperature sensor designed for boiler supply temperature control. HERZ defines this thermostat as a proportional controller that requires no auxiliary energy. It is intended for temperature control and/or limitation in hot-water circuits and air heaters.

The thermostat consists of a thermostatic head with a liquid-filled hydrosensor, capillary tube, pipe contact sensor and fastening material for fixing the sensor to the pipe. For the HERZ 7421 model, the set-point range is 40–70 °C, the capillary tube length is 2000 mm and the threaded connection is M28 x 1.5.

The operating principle is mechanical. Changes in temperature cause a change in the volume of the liquid filling inside the hydrosensor. This movement is transmitted through the capillary tube to a bellows system, which actuates the valve spindle. When the pipe temperature rises, the thermostatic valve closes. The temperature adjustment scale is located directly on the handwheel.

Technical information:

Manufacturer: HERZ

Product type: thermostat with contact sensor

HERZ series: 7421

Manufacturer code: 1742100 / 1 7421 00

Application: boiler supply temperature control

Control principle: proportional controller without auxiliary energy

Set-point range: 40–70 °C

Connection thread: M28 x 1.5

Sensor type: liquid-filled sensor / hydrosensor

Temperature sensor design: pipe contact sensor

Capillary tube length: 2000 mm

Handwheel colour: white

Maximum differential pressure: 0.75 bar

Recommended maximum differential pressure for low-noise operation: 0.2 bar

Hysteresis: 0.3 K

Effect of heating medium temperature: 0.15 K / 10 K

Excess-temperature safety function: 10 K above the maximum scale value

Maximum storage temperature: 50 °C

Power supply: not required

Compatibility: HERZ valves suitable for thermostatic operation.

Temperature setting scale:

Position 1: approximately 40 °C

Position 2: approximately 45 °C

Position 3: approximately 50 °C

Position 4: approximately 55 °C

Position 5: approximately 60 °C

Position 6: approximately 65 °C

Position 7: approximately 70 °C.

Installation:

Unscrew the screw cap or handwheel from the thermostatic valve body. With the thermostatic head completely open, place the union nut on the valve and turn the thermostatic head so that the handwheel scale can be read easily. HERZ specifies that the union nut should be tightened moderately using a 30 mm open-end wrench. After installation, test for proper operation and set the thermostat to the required temperature.

The contact sensor and its base are attached to the pipe using clips. HERZ also states that the sensor can be placed in an immersion sleeve. Proper heat transmission between the pipe and the sensor must be ensured.