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I wqant to add a wifi thermostat to a millivolt system. I would like to keep the current thermostat in case of power lost so that it would kick in at a minimum temp say 45 degrees. How do you wire a thermostat in parallel? Thanks

marked as duplicate by Niall C. Aug 29 '16 at 16:04

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  • If i read the wifi thermostat directions it says all the battery does is keep it from loosing the settings and does not operate the thermostat. I have a vented heater with no electric to it which will operate if the power would go off. So my concern is if power goes off and the wifi thermostat does not work to statrt heater i need a backup thermostat to start the heater. I have a Honeywell wifi thermostat. Thanks – user59457 Aug 29 '16 at 15:15
  • How would the other thermostat work in case of power loss? If there's no power, your furnace won't kick in. – Chris Cudmore Aug 29 '16 at 15:41
  • Its a millivolt thermostat that controls a vented heater. No power to the heater just the pilot – user56392 Aug 29 '16 at 19:47
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First of all, most if not all "wifi" thermostats have a battery backup so the thermostat keeps working even if the wifi goes down.

Second, if you lose power, how do you expect your furnace to keep running? Your existing thermostat runs on electricity too.

  • In a millivolt system -- the electricity for the thermostat and gas valve is generated by the furnace itselsf – ThreePhaseEel Jul 15 '16 at 22:09
  • @ThreePhaseEel I'm not familiar w/ this-- so if the furnace shuts down, is there built-in battery backup? – Carl Witthoft Jul 15 '16 at 22:25
  • The thermopile that generates the power for the 'stat and gas valve sits in the pilot flame -- that way, the only way it'd shut off is if the pilot blew out, which should shut down the whole show anyway to avoid KABOOM. – ThreePhaseEel Jul 15 '16 at 22:38
  • @ThreePhaseEel ahhh... I'm more accustomed to non-pilot systems which depend on a spark to ignite :-) – Carl Witthoft Jul 16 '16 at 11:34

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