Why is it important to carry out a thermal audit?

Carrying out a complete, reliable heat balance allows you to consider which management solutions best suit your needs.

First of all, it is essential to identify the most delicate devices or functions: the ones that should be given protection priority. Delicate devices can be the cause of shut-downs or malfunctions of the installation.

Important to know:
– Critical temperature of device
– Critical humidity level for each device

Recommended operating temperature (in degree celsius) maximum temperature with the risk of malfunction granted
variable speed drives 35 50
programmable logic controller 35 40-45
contractors 45 50
circuit breakers 45 50
fuses 50 50
power supply 35 40
printed circuit boards (PCBs) 30 40
electric batteries (accumulators) 20-25 30
telecommunications equipment 40-50 55
battery of capacitors 50 55


Expert Tip:
The thermal management solution must be sized according to the critical temperature of the most delicate element of the enclosure. This temperature should never be exceeded.
The mean working temperature recommended for the inside of the enclosure is 35°C. This is the reference temperature for the control equipment integrated in the thermal solution.

Internal Analysis

1. Measuring the air temperature inside the enclosure. The measurement of air temperature inside the enclosure must be taken over a complete period.This data will be used to:
– Complete the overall thermal analysis
– Avoid exceeding the critical temperature of each device
– Calculate the loss of power (W) of each device

Expert Tip:
The temperature measurement inside the enclosure should be taken in three separate areas (T1, T2 and T3). Avoid the ventilated hot-air outlet.
Mean temperature of enclosure = (T1 + T2 + T3) / 3.

2. Measuring losses of power (W)
Before performing the thermal calculation, it is important to have detailed information of the dissipation value of each component. Generally speaking, this value is not easy to find.

External Analysis

1. Measuring the air temperature ( °C )To ensure reliable calculations, the external temperature measurement should be taken over a complete period.

What to measure:
– Max. mean temperature
– Min. mean temperature

2. Measuring the humidity level (%)
This consists of determining whether the environment is:
– Dry: Humidity level < 60%
– Humid: Humidity level between 60% and 90%
– Very humid: Humidity level >90%
Temperature variations detected in the environment will let you know whether or not there is condensation

3. Analysis of air quality
It is essential to measure and analyse air quality in the installation area of the control enclosure.
A prior inspection of the installation site is generally enough to identify the constraints to which the electrical and electronic devices will be exposed.

By analysing these factors, you can choose the right thermal solution. You are able to size properly, optimize performance and avoid local thermal issues.


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