Installing wifi thermostat to boiler system

Old 11-04-20, 06:42 AM
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Installing wifi thermostat to boiler system

Have a pretty basic Honeywell digital thermostat hooked up to my cottages gas
boiler system ( No AC) and would like to replace it with the Honeywell RTH6580WF smart thermostat. The existing wiring it connected to R and W no extra wires in the wall and the thermostat is battery powered, is a C wire needed and do I need any other connections from the furnace.
Old 11-04-20, 06:55 AM
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Yes, a C wire is required. See manual: Here is another option that doesn't require a C wire, but it is not WiFi enabled: Honeywell TH6100AF2004
Old 11-04-20, 07:07 AM
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Hi, yes you will need a 3rd conductor, it maybe best to pull a new 18/3 thermostat cable from the boiler to the Stat, post some pics of your boiler controls and we can assist with the connections, good choice for the Stat.
Old 11-04-20, 05:30 PM
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Electronic thermostats are powered with 24 volts AC on terminals C and RH.

There is a an alternative to installing new 3 wire cable.

Near thermostat install a 120 volt - 24 volt adapter and connect to C and RH. Existing two wires still go to RH and W.

It is an easy way to upgrade older home that have thermostats on 2nd and 3rd floors.

No other connections are need from boiler unless there is a fan on system.

Last edited by doughess; 11-04-20 at 07:19 PM.

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