Sensor 3 Overtemp Operation

Symptoms

Sensor CEM processor is displaying Overtemp Error for one or more dimmers.

Explanation of Issue

This issue is most often caused by one or more dimmer modules, rather than the CEM. The CEM circuitry receives overtemp signals from the dimmer modules; it does not generate these signals on its own. It is far more likely that a CEM would fail to detect an overtemp error than that it would generate a false one.

It is possible that corrosion on the CEM can generate an overtemp signal. However, in this case, there would likely be other problems with the CEM, and possibly the entire rack, if corrosion is found.

When a dimmer's internal sensors indicate it is running too hot, it sends the signal to the CEM, which then reports an overtemp error on that dimmer.

Dimmer modules which are reporting a true overtemp error can be hot enough to cause burns when touched. Please exercise caution if your rack is reporting an overtemp error.

Additional notes:

• Overtemp is not an AF function. Overtemp errors are generated independent of AF cards that are in the rack.
• Overtemp messages only appear after the dimmers are brought to a level above 0%.
• Overtemp is a bussed signal. This means that if a module is reporting an Overtemp error, it can cause Overtemp errors for adjacent modules to appear.

Solution

It is recommended to de-energize the rack to unseat and re-seat modules. Seating modules while energized could could cause damage to both the rack and the dimmer modules. Sensor racks cannot be de-energized locally; this operation must be performed at the upstream power feed.

1. Check the CEM overtemp error(s) to determine which module is reporting the signal.
2. De-energize the rack. Pull the CEM to check for any corrosion damage. If no corrosion is visible, put the CEM back in and proceed to step 3.
   1. If corrosion is found on the CEM circuit board, inspect the rack and modules to see if more corrosion exists and proceed to step 7.
3. Unseat the suspect dimmer module. Leave the module in the rack but pulled out about halfway so the slot isn't fully open. Open slots in a sensor rack pose a life-safety risk due to potential arc flash.
   1. If there are multiple suspect dimmer modules, unseat all the suspect modules.
4. Re-energize the rack and send a level greater than 0% to all dimmers (source does not matter, local control is easiest). If an error returns, clear the error on the CEM (may need to hold clear for 10 seconds) and check if the error returns again on any circuits. If errors appear again, return to step 3, de-energizing the rack as necessary until no errors appear.
5. Re-seat each dimmer module one at a time and set the dimmers to above 0% (20% is a good starting point), de-energizing and re-energizing as recommended.
6. If the error does return, note the dimmer module, de-energize the rack, unseat it again, then continue testing the remaining modules one at a time. Again, leave the modules in the rack but pulled out about halfway so the slots aren't fully open.
   1. Modules can also be swapped to other slots to see if the error follows the modules. If multiple modules are reporting errors, remove those modules together and move them to other slots, keeping them adjacent to one another.
7. Contact ETC to begin the RMA process for any problem units.