Troubleshooting, SCADA and Energized Work
This is a great followup and use case for a home energy monitoring system, something I wrote about on the blog last week.
My new ETS was broken, but how?
The electric thermal storage (ETS) unit mentioned in that post stopped doing what its supposed to.
When we had it installed I didn't tie it into the PLC because of time commitments, so the contractor put a programmable thermostat in as the charge controller. If its within the right time AND the temperature in the room is lower than the setpoint it start charging. The internal charge thermostats turn off the charging for the three rows of bricks.
This weekend we noticed that the unit didn't stop when it was supposed to. We also had a minor flood in the basement this weekend so I put the thermostat in manual to just get the heat going to dry it out, so we initially thought that was the problem. Turns out, no, it was something bigger.
Before we even had to break out the control schematics, we were able to figure out what was likely going on.
SCADA as a troubleshooting tool
By using the heating screen on the SCADA, the backbone of the Home Energy Monitoring System, we were able to troubleshoot the system without exposing ourselves to 208V. All the covers could stay closed.
To do that we monitored the power output from the unit modifying the various controls that would turn the unit off. When the only action that would shut it down was the breaker we took to google.
Turns out that these units have a failure mode that the charge controlling relay "sticks", and that is where I will get looking today to find out if there is anything that I can do to fix it.
Moral of the story
This isn't about the home energy monitor, basement floods, or even ETS; this is an example of using properly calibrated (and tested) SCADA and troubleshooting procedures to identify the likely culprit to an issue before opening a panel.
CSA Z462 and NFAP 70E have a provision where you don't need an Energized Work Permit for troubleshooting, because troubleshooting isn't "work". While troubleshooting energized isn't "wrong" that doesn't mean that its safe.
When you have input during a control system or SCADA upgrade, include provision for troubleshooting telemetry and using a platform like VTScada the cost per IO (in SCADA hardware and licenses) is minimal when compared to a safety incident.
This same telemetry can be used for advanced asset management which has other business applications.
Don't expose yourself to energized parts, unless there really is no other option.
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