Thermostat with ST when Internet goes out

Hey guys, I live in a very remote and cold area. My home has an older furnace (no C wire or a/c) and I’d like to use a smart thermostat to save money in the winter. My question is, if I get one of the cheaper “dumb” Z-Wave thermostats and I lose internet while out of town (happens from time to time due to ice/snow), will my thermostat basically lose all functionality? My worst fear is pipes freezing and bursting. If I get an ecobee instead, does that have a fall back that can run without Internet?

It will lose any remote functionality. Whether or not your schedule will run or any rules will activate will depend on the DTH you use. As I understand it, if you use a custom DTH it will be running in the cloud so without internet it will become a dumb thermostat until you get internet back. If you use a ST DTH it may run locally so schedules and rules may still function. Still no remote capability without internet though.

It should maintain the last temp set in any case.

The Ecobees are true “smart” t-stats in that their normal programming and processing is all on-board, and internet connectivity is needed only for remote control and/or monitoring. If you lose that connectivity they will continue to operate per their programming.


Plus, they have a 5 wire to 4 wire converter for the furnace to get you that C wire.

I’m not sure that’s true.

Since only smart lighting can run automations locally, even if one were using a stock thermostat DTH that was eligible to run locally, it wouldn’t be possible for a smartapp to change thermostat modes or set points when the internet is down. I suppose if the thermostat has a switch capability, smart lighting automations that turn the thermostat on or off could still run, but that doesn’t seem to be that useful.

I think that’s correct.

Even if you get a basic one with remote access, the local programming (that which is stored directly in the unit) should run as a normal “dumb” therm.

SmartThings “could” be used to override the internal settings but I think most smart therms should work regardless if remote access becomes unavailable because of the internet or lack thereof.

I did say “may” run, as I was not sure since I don’t run a thermostat on ST and I am not 100% sure what does or doesn’t run locally.

I think rontally’s assessment is correct, Most are just going to become like a normal thermostat once internet connection is lost and only manual intervention is going to change it, unless the dumb thermostat has internal abilities that can be programmed at the thermostat itself.

No worries. I don’t have a thermostat either, but I am quite sure that smart lighting, and some functions of smart home monitor, are the only smartapps that can run locally.

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