This part of ISO 23551 specifies safety, constructional, and performance requirements and testing of mechanical gas thermostat for gas burners, gas appliances, and similar use hereafter referred to as “thermostats”.

This part of ISO 23551 covers type testing only.

This part of ISO 23551 applies to mechanical gas thermostats of nominal connection sizes up to and including DN 50 with declared maximum inlet pressures up to and including 50 kPa for burners and gas-burning appliances using fuel gases as natural gas, manufactured gas, and liquefied petroleum gas (LPG).

This part of ISO 23551 applies to mechanical thermostats controlling the gas flow directly or indirectly through an integral gas valve and which do not require external electrical energy for their operation.

This part of ISO 23551 only applies to mechanical thermostats used on gas appliances where the thermostat is not directly exposed to the outdoor environment.

This part of ISO 23551 only applies to mechanical thermostats which are intended for operating control functions.