Is the T40K not as sensitive to this System Protect error? I have two T2000 Tstats but I only seem to get this error on our upstairs Tstat. Both the downstairs and upstairs systems work off he same furnace and AC unit. It’s bizarre.we have two zones but only one furnace and one 5 ton AC unit.
Neither the T40K or T2000 are affected by the sensitivity to voltage variation like the T3000 is.
This thread is referencing the T3000. The T3000 thermostats used digital relays which were extremely sensitive to it, requiring isolation relays in many cases.
The T40K uses mechanical relays like the T2000 and is not as susceptible to this issue.
If you are seeing issues on a T2000 though, it is likely to also occur on the T40K and would need resolved through an isolation relay most likely. It may be impacted by wiring, which may be why one encounters it and the other does not. It could also potentially be an issue internal with that thermostat in particular, but it’s more likely not.
The HVAC guy came today to do the annual AC check for the upcoming summer season. Both the upstairs and downstairs T2000 thermostats went into System Protect when the AC was turned on. He said after 5 minutes the AC turned on… and it stayed on, so it wasn’t going into any protect mode once it engaged. He spent along time verifying that the wiring was done correctly and tested the wires to verify they are intact (we have had mice). He said the wiring was correct. He didn’t have a relay on him, so he couldn’t install one. He was wondering since the thermostat control screen in the alarm.com app has the compressor set to a 5 min delay, would that cause the thermostat to read the draw funny and go into System Protect?
Looking at your account I see two thermostats, Upstairs and Downstairs, and they are both T3000s, not T2000s.
The official description of that System Protect message from ADC:
System Protect is a 5-minute delay prior to calling for heating or cooling to protect the system from short cycling. It is only applied if the thermostat has detected an unexpected relay state internal to the thermostat during a call.
System Protect is intended to cover rare cases of power issues with the HVAC system. If System Protect is being seen frequently or appears on every call for heat or cool, it points to poor HVAC performance or pre-existing incompatibility. If System Protect occurs while the thermostat is in cooling mode, and the R wire is in Rh, this may be resolved by moving the R wire to Rc and reconfiguring the thermostat.
Frequent or extreme System Protect delays can be resolved by installing an isolation relay.
Ok. I thought I have T2000 as I definitely have them at work. Interestingly I don’t have the same errors at work so that really does suggest that T2000 is less sensitive than the T3000. Since I’m already using the Rc it looks like I’ll need an isolation relay for the Y. I’ll double check the W (heat) before calling them back. Thank you for finding my error and providing advice 
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