Just got my Honeywell wifi thermostat (5 wire) working with my 4 wire setup, but I do have a blue wire that seems to not be grounded (fifth wire was hiding in the wall)....

....So, I took the white (heat) wire and used that as the common (because it works and I don't need heat for a few months)

But I would like to use the obvious 5th wire (blue) to hook up to the common ground on the thermostat.

I haven't taken a look at the heating/cooling unit (forced air/heat(gas)/ac+compressor) in the attic/ceiling because I have to empty a closet to get to the access panel to get to the unit.

My question is this. Before I empty the closet, climb into the attic etc, if my heating/cooling unit doesn't have a C (common) port to put the blue wire (which is what I suspect) can I just ground it somewhere?

I assume for the thermostat to function etc it just needs the 24 AC volts between the Red and Blue.

I would assume the blue (common in my case) just needs to be grounded or hooked up to a C terminal on my unit if I am lucky enough to have one.

Let me know if there are any questions or concerns.

Please don't feel the need to dumb things down for me, EE and COE experience here.

submitted by /u/javi404
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