Page 122 - General_Purpose_Enclosures _Aria, APO,Polysafe

122 GENER AL PURPOSE ENCLOSURES HE AV Y DUT Y AND INDUSTRIAL ENCLOSURES

—
Accessories
Heater units

Function Advantages
Small heaters for electrical enclosures are • Energy efficiency
important accessories for ensuring the • Dynamic heating
operational safety of control and distribution • Self-regulating
assemblies. • Self-limiting
They are essentially used to prevent the • Quick clip-in fitting
formation of condensation or to ensure that • Zero maintenance
a minimum temperature is maintained inside the • Long service life
electrical enclosures, i.e. at a few degrees above • Compact unit
ambient temperature.
Standards
Operating principle EN 60335-1 / EN 62233
The small heaters are equipped with PTC heating UL
resistors (semiconductors with a positive EAC
temperature coefficient). The self-regulating and
self-limiting semiconductor heating elements Applications
maintain a constant temperature over the heating Electrical enclosures, instrumentation units,
surface of the small heaters. The aluminum body display panels, control cabinets,
transfers heat to the surrounding air through ATM machines, access control system for parking
natural radiation. Special extruded profiles lots, etc.
guarantee perfect heat radiation.
Installation
Calculation model for determining the power re- Quick installation on 35 mm DIN rail (EN 50 022).
quirement Recommended installation in the lower section of
According to the formula: P = A x ∆T x k the enclosure, at least 40 mm from the equipment
P = power to be supplied via the resistor (W) itself.
A = exterior free surface of the enclosure (m2)
∆T = temperature difference between the
interior temperature after heating and the
exterior temperature in °K.
k = thermal radiation coefficient:
steel: 5.5 W/m2K
polyester: 3.5 W/m2K

3
Rule of thumb: recommended value 100 W/m of
enclosure volume. The calorific value must be
doubled for an exterior installation. Multiple small
heaters are preferable to a single heater unit.