New to site and think this is fantastic. Thanks in advance for any help.

I have searched and found postings close to my issue but not exactly. Even on this climatouch c3.

I have a white rodgers 4 wire single transformer set up. I tried to install my new c3 and hooked it up the same as the white rodgers. It powers up then dies off as soon as the first load is energized (green fan or white heat). The rules talk about needing to hook up to the common. I tried to use the extra blue wire and connected it to the blue c on the furnace terminal strip. At the stat I connected it to the RC and removed the jumper between the RC and RH. This blew the 3 amp fuse immediately.

It looks to me like the stat is connecting the 24 volt hot from the red wire to the common and that's obviously a short blowing my fuse. I can't find what is supposed to be the common on this stat? It only has the RH and the RC and no common? The rules also talk about adding resistors between terminals but I am still believing there is a simple way to use this extra blue wire and tie in the common. I could even run it to the common side of the transformer at the furnace but I don't know what's common for the stat?

I have some 100 va transformers with resets on my van. Can I just install a bigger transformer to carry the load of the stat and still use the 4 wire single transformer?

Again thanks in advance for any help.

David

After some further investigation I saw the thermostat has a C (common) screw on the thermostat. I don't know how I missed it the first time around. I ran the blue wire from the furnace terminal strip C to the C on the stat and everything is fine.

David