I have read most of the posts here and have a specific question about my install. In the picture you can see the 3 blue wires coming off the 24v side of the transformer. One goes to the side and than another blue wire is connected to the metal and goes to the ac unit outside. One goes up to what I believe is the exhaust fan. The last one connects to the circuit board. There is also a 24v HUM screw on the board. My question is should I connect to the 24v Terminal on the board or one of the wires that are screwed into the metal next to the transformer. Thanks for any help.
Best Answer
You should be able to connect to any of the blue wires, or to the chassis where the transformer is bonded. I wouldn't use the HUM terminal, unless you've looked at the schematic and determined that it's connected directly to the transformer. If you include the model number, or a photo of the schematic. We'd be able to tell you for sure.
If you're supplying an A/C unit contactor, the furnace circuit board, and an exhaust fan from this transformer. You may find that it doesn't have the power to also supply a thermostat. There may be no problem at all, but it's something to be aware of.