Issue
Controller loses data following power failure or mains noise (from transients or spikes).
Product Line
Andover Continuum
Environment
All CX, ACX, i2, bCX, b3 controllers
Cause
Controllers are exposed to operating conditions outside their operating envelope and tested limits. This can cause them to reset, go offline or lose data.
In extreme circumstances, poor installation can take controllers outside their operating envelope and cause damage requiring a repair.
Resolution
If a controller is setup on a bench with a clean power supply and the correct grounding, you will be able to turn off/ on the power and the controller will warm start every time.
This test will confirm the controller is operating correctly, not faulty and that the software settings are correctly set for warm starting. Also that the RAM backup battery is connected and operating.
If site resets, lockups, loss of memory or other corruption are seen on a site, then here are some of the installation issues to consider:
- Grounding - All controllers require a clean low impedance earth to sink all of the noise and emission energy a controller may be exposed to. The noise protection circuitry within a controller is designed to dissipate this energy down to earth, if this path is not low impedance the energy can cause a controller to reset or even be damaged permanently.
- Shared Ground - The earth cable to the Controller should not be shared with any other equipment that is a high inductive or capacitive load, these can generate noise spikes back into the controller. This includes motors (pumps/ fans etc) lighting circuits (capacitive loads), inverters (high frequency noise).
- Induced emissions - The controller should not be installed near any equipment that may induce excessive radiated emissions into the unit, the radiated emissions from Motors, inverters, radio & microwave equipment, lighting circuits, power wiring can all produce radiated emissions that could exceed the specified limits of the Controllers.
By fitting the controllers into earthed metal enclosures you can minimize the external emissions by effectively creating a Faraday cage protecting the controllers circuitry. - Power feed - The power requirements for every controller is defined in its datasheet with the defined tolerance, taking the power levels outside these limits can cause incorrect operation.
- Power spikes - Surges or spikes in power feeds or connection I/O cabling can cause controllers to reset, lose data or even become damaged. Fitting varistors to the power supplies and across any output loads can minimize the impact on the controller, See What Varistors should be used?.
- Shared Supply - The power feed to a controller should never be shared with other equipment that can generate electrical noise. Never use the same supply to power both controllers and field equipment like valve/ damper actuators in BMS systems or magnetic door locks in Access control, both actuators and the solenoids in Mag locks can generate large back EMF pulses into the controllers that can cause resets or even damage..
Fitting power filters or an external UPS on the controller can protect it from spikes on power up/ down, it is however always best to remove the noise spikes at source, so fit filters the generators, motors, contactors etc.
It is also possible for the above issues to cause Infinet networks to Reconfig as well as other networking problems.
Note: All controllers are approved and tested to the defined limits for FCC and CE induced and radiated emissions as detailed in the datasheets, for a controller to fail, restart or lose data it must be exposed to levels exceeding these specifications.
They are not however power equipment and cannot be exposed to the noise levels power and industrial controls equipment is designed to withstand.
