Thermostat wiring with Honeywell K wire

Hi, the compatibility checker has me a little confused.
If I select R along with W and C then my system is not compatible but if I select RC (bridged with R) then it becomes compatible.
I’ve also noticed the lack of option for K which according to the knowledgebase below is specific to Honeywell thermostats without C wire.
Expert guidance appreciated


Welcome to the Wyze community @thangng3!
I’m not an expert but @WyzeChuan is! I’ll see if he has the answer.

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The jumper between RC and R is if you have one transformer powering the system. If there was two transformers, there would be a wire to RC, and another to R. The typical setup is one transformer (inside the furnace/air handler).

Honeywell wire saver modules combine the Y and G wires to form a single K wire that connects to the K terminal on some Honeywell thermostats. It’s used for systems that don’t provide a C wire but have a thermostat that requires one. You may have one inside your furnace/air handler which looks like the example below.

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