The temperature class and surface temperature, a monitoring unit (level, flow rate) if applicable and further operating conditions (ambient temperature range, self-heating, conduction of heat, mounting orientation, etc.) have to be fixed with the testing of the complete heating construction.
The used safety devices for limiting the temperature, monitoring the flow rate and/or monitoring the level have to be suitable for this purpose and have to be certified.
The heater with flow rate monitoring may only be used when the flow rate is above the minimum flow rate that was basis for the temperature measurement.
The heater with level monitoring may only be used when the level is above the minimum level that was basis for the temperature measurement.
In case of medium temperatures at the outgoing part that were higher than the temperature class of the heater, the thermal isolation has to be taken into account for the explosion protection measure.
In addition to the surface temperature of the box, other parts (e.g. flange, nameplate, valves and accessories, etc.) that can be heated impermissible have to be part of the isolation or the thermal conductance have to be suppressed.
The thermal isolation has to prevent the migration of gases and vapours of the surrounding environment to the hot parts.
The thermal isolation is not subject of this type examination.
The positioning of the temperature sensors for the temperature limiter has to be carried out in such a way, that the detection of a failure of one phase is included.
The conditions of safe use of the separately certified equipment / components have to be taken into account.