What is a normal temperature for a x20CP0484?
There is an maximum of 105 degree in the specs.
But what is a normal temperature window of CPU of the PLC?
On what temperature do you need to set a warning to the operator?
Greatings, Luc
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That is a limit where the CPU will protect itself by changing into service mode!
So any time before that would be a good time to warn I guess?! 
Considering normal circumstances that shouldn’t happen imho. At least if you stick to the max allowed specs:
hor: -25 bis 60°C
vert: -25 bis 50°C
Edit: The actual temperature of the CPU depends highly on your environment temperature, so if you have around 20°C the CPU will probably be around 40-50 °C, assuming air flow is not blocked.
Best regards,
Well our CPU is never under the 70 degree, even on my desk with nothing that can block the cooling of the CPU…
So what should it be normally?
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Well you can’t say “normally” I guess. The PLC running here in the cabinet has 39 °C…
Second biggest influence beneath env. temperature will probably be the CPU load…
I don’t know of any charts provided by B&R for load / temperature…
So now you could setup a test environment with variable temperature and load values to record the “normal” values 
But as mentioned above, normal is relative…
Best regards,
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1: typical ambient temperature
At an ambient temperature of 25°C, a temperature of 70°C measured on the CPU is quite normal.
In the IO Mapping of the controller, two measured values ​​are provided in this regard. One measuring point directly on the CPU and a second inside the housing in the vicinity of the circuit board. A meaningful measurement of the ambient temperature cannot be provided.
If the ambient temperature rises by 10 degrees, the CPU and housing temperature also typically rise by 10 degrees.
Note. The CPU temperature also depends on other factors such as the installation position and the CPU load.
2: integrated protective function
The control has an integrated protective function that protects the device at a component temperature of 105 °C.
Controller Datasheet:
3: application area of ​​a control system
However, as a user of controls, you “only” have to pay attention to the actual control cabinet or ambient temperature outside the housing. B&R carries out numerous climate tank tests to ensure the following ambient temperatures:
Datasheet X20CP048x
If the device has been installed correctly and the distances to the cable ducts and control cabinet walls described in the user manual are correct, you can rely on safe operation within these limits.
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Thanks for your answer,
I am wondering what then the right limits are. For example we give a CPU warning at 89 degree. But is that a good temperature? I dont know what the temperature in the cabinet is at that moment. But we have many customers that have the CPU on that temperture.
It doesn’t feel good that the CPU reach that temperature but what is good?
If ambiant/cabinet temperature is below 60 degree is the PLC then also 70 degree? I dont think so…
If the ambient temperature rises by 10 degrees, the CPU and housing temperature also typically rise by 10 degrees.
So if its 20 degree at my desk and my cpu is now 70 degree… At 60 degree my cpu will rise by 40 degree so my cpu will be 110 degree? 
1: switch off temperature
The switch-off temperature of the safety function is 105 degrees. That is below the specified temp in the data sheet and thus protects the HW.
2: operation Temp
I am wondering what then the right limits are. For example we give a CPU warning at 89 degree. But is that a good temperature?
That’s OK. The customer’s control cabinet will probably be around 40 degrees.
I dont know what the temperature in the cabinet is at that moment. But we have many customers that have the CPU on that temperture.
The temperature provided in the IO assignment is only a guideline. If the suspicion that the customer has a temperature problem in the control cabinet is confirmed, the control cabinet environment should be measured. B&R provides the X20 modules: X20CMR010, X20CMR011, X20CMR111,
X20CMR100 for the analysis. These modules were designed for this application.
https://www.br-automation.com/de-at/produkte/io-systeme/x20-system/sonstige-funktionen/x20cmr010/
To show that these temperatures are typical for CPUs and to allay any fears, I have another example. I have just read the temperatures of my notebook:
So if its 20 degree at my desk and my cpu is now 70 degree… At 60 degree my cpu will rise by 40 degree so my cpu will be 110 degree?
yes, at an ambient temperature of 60 degrees, the CPU temperature will also be just below the shutdown limit.
Note 1:
The CPU is lying flat on the table? That is actually not a permissible mounting direction. The air cannot circulate.
The control cabinet temperature is also important if the control system has not yet switched off because the service life can then no longer be guaranteed. This also applies to the housing plastic.
In summary:
If you want to do absolutely the right thing, you have to monitor the control cabinet temperature and check the installation position of the X20 components.
Do you need a quick, cheap solution? Look at the CPU temperature in a control cabinet at 50 degrees and use this temperature as a limit for the warning.
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Hi Luc, welcome in our community. You got a lot of good ideas about your topic. Please in the end, do not forget to mark one that helped you the most as a solution. So others can use it later on as well. 