There are a couple of alarms you can set up.
For heaters, wattage drop works well. Here's one of my heater failure virtual outputs:
[Heat1FailLoc]
Set OFF
Defer 000:10 Then OFF
If Output Heater1 Watts < 75 Then ON
Defer 000:10 Then ON
When On > 000:05 Then ON
Then in your alarm output:
If Output Heat1FailLoc = ON Then ON
What this will do is send you an alarm and lock it ON if your heater wattage drops below 75 for 10 seconds.
To determine what wattage to use, look at the Input Log graph for each heater wattage; it will be labeled 'HeaternameW'.
The alarm then won't stop until you switch the VO to OFF for a few seconds (and then back to AUTO to re-arm it.)
Another thing you can do is set an alarm if your heater or heaters stay on continuously for longer than they ever normally would. Another VO:
[HeaterErr090]
Set OFF
If Temp < 70.0 Then ON
If Output Heater1 = ON Then ON
If Output Heater2 = ON Then ON
If Output BackupHeater = ON Then ON
Defer 090:00 Then ON
Then in your alarm output:
If Output HeaterErr090 = ON Then ON
For my system if any heater or combination of heaters stays on for more than 90 minutes continuously, something is wrong.
For this one, it's a good idea to look at your Output Log to determine the longest period of time that your heaters ever normally stay on.
This will also alert you if your temperature probe fails. When temp probes fail, they will read an impossibly low number.
fantastic, thank you!