If you’ve noticed that your ecobee seems to be constantly rebooting, there may be a few things to examine.
Problem with your furnace
If your ecobee is only rebooting when calling for heat, this is indicative of the high-limit switch on your furnace being triggered.
A high-limit switch is a protective part of a furnace designed to keep the mechanism from overheating itself. A furnace is at a risk of overheating any time airflow is limited from passing through the heat exchanger. Because ecobee thermostats require a C wire and run directly from the 24V supplied by the furnace, you may notice that your thermostat screen is black after several minutes of running the heat. This is because the high limit switch is tripping and cutting all 24V to the system.
When the high limit switch trips and the ecobee powers down, you will likely notice that the fan in the furnace continues to run for a short period without the burners before power is restored to the system. This ensures continuous airflow through the HVAC system and assists with cooling things down.
You may note that this never happened on your previous thermostat because your old thermostat was battery powered; if the furnace cuts out, there is no visual indicator to know that the high-limit switch has tripped and the furnace simply starts up again when the switch resets.
There are several things that could cause a high limit switch to trip. These include, but are not limited to:
Restriction of airflow
- Too many vents closed off in your home
- Damaged or dirty furnace filters
- Dirt in the blower motor housing
- Plugged secondary heat-exchanger (high-efficiency furnaces only)
- Plugged AC Evaporator Coil
Over-Amping of electrical components
- Failing fan motors can overall pull more amperage causing the switch to trip
- Any other part of the system pulling more amperage than normal
- The belt on a belt-driven fan motor may be too loose or too tight
Bad High Limit Switch
- It is entirely possible that the switch itself is bad. The switch is a very simple mechanical part and is prone to wear and tear.
Problem with your float switch
If your ecobee is only rebooting when calling for cooling, this is often indicative of your float switch being tripped.
You may have a safety device installed at your furnace to prevent damage to your equipment as a result of the condensation that's produced when you run your air conditioner. These safety devices include float switches, wet/safety switches, condensation pumps, and drip pans. They are usually wired into the R terminal on the furnace (you'll see an additional wire on the R terminal/spliced into the R wire and should be able to trace it back to the safety device).
When condensation begins to gather and has no way of draining properly, power to the thermostat will be cut. In order to restore power to the thermostat, check your safety device to ensure that water is draining properly. If you notice that the drip pan is full, empty it and clear any potential blockages.
An example of a safety switch An example of a condensate pump
An example of a drip pan—check to see if the pan is full of water