How to Minimize Thermal Drift in Outdoor Electrical Enclosures
Temperature control of outdoor electrical enclosures is a tricky affair. The calculation of heat load in these enclosures has to factor in solar heat gain and heat due to ambient temperatures apart from the heat load from the electrical equipment inside. Due to fluctuations in ambient temperature and the day-night cycling of solar heat, outdoor electrical enclosures are subject to thermal drift, the temperature change caused by internal heat loads in equipment and changes in the external ambient temperature. Some electrical equipment such as relays and switches have thermal drift compensating circuits in their components. For instance, BJTs and Op-Amps have internal circuits that compensate for thermal drift due to internal heating and offer precise equipment operation even at increased temperatures.
Why Thermal Drift occurs
Thermal drift in outdoor electrical enclosures is due to equipment heat load and daily pattern of ambient temperature around the enclosure. Since some manufacturers design equipment to compensate for thermal drift due to internal heat, ambient temperature can be understood as being the major contributor. Thermal drift of equipment in an enclosure depends on several factors:
- The material of the enclosure
- Type of insulation used
- Altitude
- Wind flow parameters in the area.
Equipment performance may be affected by thermal drift, more so in outdoor enclosures since multiple factors contribute to increase in equipment temperature.
Impact of Thermal Drift on Equipment
Thermal drift is an undesirable phenomenon that particularly affects metrology and control equipment. These equipment are highly sensitive to temperature increase. Some manufacturers provide a compensating circuit that negates the effect of increase in temperature. However, thermal drift affects the optimum performance of most equipment. To illustrate an example, mechanical, solid-state and microprocessor-based relays have components with a certain resistance that have a high temperature coefficient. High temperature operation can cause setting drift of the relay thus preventing it from switching at the right time that can be harmful to the equipment being controlled.
How to Minimize Thermal Drift in Outdoor Enclosures
Use of Closed-Loop Cooling Systems
In outdoor electrical enclosures with equipment that are used for precise control, switching and measurement purposes for your business, it is wise to opt for enclosure air conditioners that can offer efficient temperature control. The use of an air conditioner with a digital programmable controller makes it easy for you to set your enclosure temperature to a desired value and ensure a quick response to fluctuating heat loads in the enclosure.
Factoring in Ambient Temperature Extremes
BTUH calculators can help size an enclosure air conditioner based on the heat loads in your outdoor electrical enclosure; however, the results of the calculator are only as good as the data entered. Many calculations are done based on the average solar exposure and average temperatures in a particular location; however it is extremely important to use the maximum values in your calculations to ensure that the enclosure air conditioner has enough cooling capacity to handle extreme conditions.
Choosing an Enclosure Air Conditioner with A Thermal Expansion Valve
An enclosure air conditioner with a thermal expansion valve is better suited for quick responses to changes in ambient temperature and solar heat gain in an outdoor electrical enclosure. It adapts the refrigerant flow to the fluctuating enclosure heat loads much better than a capillary tube. Some manufacturers provide enclosure air conditioners with thermal expansion valves as part of the standard design.
Changing the Enclosure Design
The color of the enclosure surface and the type of insulation provided in the enclosure can provide a dramatic change in enclosure temperature. Ideally, an outdoor electrical enclosure should be a NEMA 4 type with a light color surface and efficient insulation layering to reduce temperature increase due to external factors.
If you are planning an outdoor electrical enclosure and need to reduce thermal drift in your equipment, speak with our experienced sales team at Thermal Edge. They can assist you in heat load calculations, air conditioner sizing and provide additional ideas that can safeguard your enclosure against daily temperature fluctuations.
