TLDR: I think I need to flip R and W wires, and to splice the blue (C) wire to the brown wire coming of the transformer. Is this correct?
Long version:
Like many others on here, I'm trying to add a C wire to my thermostat, and to my furnace so that I can use a smarter thermostat.
The thermostat has the red and white wires connected to their respective R and W terminals. The blue wire is present, but not connected.
According to my understanding of how thermostats are supposed to work, the R wire is supposed to be connected to 24v, while the W wire is energized only when the thermostat is calling for heat.
On my furnace, however, P3-9, the always-energized 24v wire, which is white, connects to T2, which is connected to the W terminal on the thermostat, and P3-7, the 'energized with heat wire' is red, but is connected to the R terminal.
Shouldn't these be switched?
Using battery power it doesn't matter, but I'm concerned that if I add a smart thermostat I'll need this to be correct.
Similarly, I believe that I can splice the Brown wire that goes from opposite the white wire on the transformer to P2-2 to the terminal block and then to the B wire going to the thermostat.
Is this correct?
I've annotated the wiring diagram with what I think are the correct fixes.
Best Answer
The only things you need is a tap from
Pinkto connect to the B common wire and to flip theredandwhitewires on theThermostat terminals:block.Write down a big W above the
T1 conn.and R below theT2 conn.label so you or whoever has to look at it later doesn't get confused.