General Selection Considerations

Heating Products

General Information

Heating products protect electronic and electrical components from temperature problems that are below acceptable tolerances. There are obvious circumstances when extremely low ambient (outside cabinet) temperatures would require a heater, but there are also less apparent times that a heater should be considered. For example, a system may run all day having its components generate heat, but once the system shuts down for the night, the quick drop in temperature could cause condensation and possibly corrosion - a heater could maintain a safe, constant temperature.

Combined Cooling and Heating

Some components today are sensitive enough that both cooling and heating could be required in the same enclosure. When designing your system, be aware of the need to maintain a relatively constant temperature inside the enclosure as ambient temperatures swing from cool to very hot. Hammond thermostats (one for heaters and one for cooling products) can control both systems automatically.

Heater Sizing Information

PH = Total power required for this Application (W)
PV = Existing power from components (W)
DT = Temperature differential (Kelvin) ambient to cabinet interior (1° Kelvin = 1° C = 1.8° F)
A = Free-standing cabinet surface area (ft²)
k = Heat transmission coefficient (W/ft²K) convection in quiet air:
 
  • Painted Steel - approx. 0.51 W/ft²K
  • Aluminum - approx. 1.115 W/ft²K
  • Plastic - approx. 0.325 W/ft²
  • Stainless Steel - approx. 0.344 W/ft²K

Formula

PH = (DT x k x A) - PV
If enclosure located outside, use x 2 (DT x k x A)  

Sample with Solution

DT = 10K
k = Painted steel = 0.51 W/ft²K
A = 50 ft²
PV = 45W
PH = (10 x 0.51 x 45) - 50
= 229.5 - 50
= 179.5W

Recommend: FLHTF200A115