ISI Marked Stem Type Thermostats - Technical Details

Contact Rating : 230 V, 20 Amps. Temperature Range : 25 - 75 °C. Tolerance on Operating Temperature : Within ±6 °C. Maximum Differential Temperature : 10 °C. Insulation Level : 1.0 KV for 1 minute. Stem Lengths available : 175 mm & 275mm.

‘BIS’ Standard. The product is covered by Bureau of Indian Standards vide IS 3017-1985 (Specification for Thermostat for use with Electric Water Heaters).

‘ISI’ MARKING LICENSE.
Our stem thermostats of 25-75º C, having stem lengths of 175 mm & 275 mm are covered under Marking License No. CM/L - 7059270

PRINCIPLE OF OPERATION.
Differential linear thermal expansion available from a combination of stem of brass tube (high thermal expansion alloy) and nickel-iron wire (very low thermal expansion alloy) is used to operate a high-precision micro-gap switch. Switch contacts open when temperature of brass stem exceeds the set temperature & close when temperature drops by the differential temperature.

As the mechanism is operated by linear thermal expansion, tolerance on operating temperature and differential temperature improve with increase in stem length.

CONSTRUCTION.
Switch is provided with heavy-duty silver cadmium oxide contacts. Contact spring is made of Beryllium Copper & scientifically heat-treated. Steatite component is used for insulation between stem & live terminals. Extra large brass terminal pillars are used for use operstion Switch base is made of high quality electrical grade material. Brass tube and nickel-iron wire are brazed together using silver alloy. 

This construction gives following advantages.

• Closer differential temperature and better repeat accuracy.
• Terminal Screws are recessed to ensure safety from electric shock.
• Terminal Screws cannot fall off.
• Specially designed Knob prevents shift in Temperature Setting during transit & vibration.
• Improved design prevents shift in Temperature Setting due to external pressure on knob.
• Contact Spring made from imported Beryllium Copper and scientifically heat-treated.
• Large size Terminal Pillars ensure cool operation at full load.
• Large size Silver Cadmium Oxide contacts give high current carrying capacity.
• Contact Insulator made of Steatite for good electrical, thermal and mechanical properties.

APPLICATION.

These are designed for use in electric water heaters & geysers, water baths, oil baths, space heating in switchboards and panels and similar other applications where temperature need to be maintained automatically. 

Note: Manufacturer reserves the right to modify specifications, design & materials of the product without notice.