I am trying to wire a tranformer into a lennox furnace, unfortunately , though she would not admit to it, the girl where I bought the transformer , pulled off at least 2 of the wires on the primary side of the old transformer, of course I wrote down which color wire came off from where , not where they were on the transformer. I need to know what connects to the following on the primary side. COM - This is Wht 120 This is blk 208 this is red, and 340, this is orange. These are the markings on the primary side. I am comfortable I know where the wires on the secondary (24 v side go) Thanks

If it is a standard gas/oil furnace you will use the white and black for 110 volt operation. If it is a electric furnace setup you will need to use th wires for 220 volts.

Is there A COM? Or is that your signoff. Com normally refers to the common wire that you use with any of the other tap points from 120 up. I would say com and 120 if that's what voltage you are using.. An ohm meter would prove this out as you would see the most resitance on the highest voltage tap and you could confirm the COM

Most multi tap transformers use Black as common, with the white wire for 120 volt, red for 208, orange for 240, and black/red for 480.

Thank You for your help. Here is the latest. I realized the lady actually gave me back a completely different transformer. I went back and she did find the right one. Now she gave me a replacement. The old one had Red and Black for the primary side, one went to one side of the power in, the other to the other side. On the secondary side , it was blue and yellow. On the new one, the secondary side was the same, no problem, on the primary side , in addition to the red and black, there was also a white and orange. I figured I would follow color code so connected the red where the old red had went and black to where the old black went. Flipped on the breaker and pow, it blew the transformer. I am assuming this means the red and black on the new one are different then the red and black on the old one. What I need to know is which of the 4 wires on the primary side should go to primary power, and Is it OK to just cap off the two wires not being used? Thanks fyi , this is strickly an electric unit, heat inside, air outside. Wiring on new primary : wht=com, Blk=120 red=208 org=240. Sorry I am a novice so I am not sure which should go where, as stated the old one only had black and red and both went to input power from the breaker box, one on one 120 side and the other on the other 120 side.

You most likely have a 230 volt unit. If so, you need to use the black & orange lines. Are you sure you don't have a short on your secondary (24 Volt ) side? Is there a fuse in the secondary line? If not you should install one, this could be what's taking out the transformer.