I have a bunn stf35 that is wired for 120V. To use it on 220V do I just connect the heater to red instead of neutral?

Does it show rated for 240VAC? If so, black and red plus a ground. You can also run a 2 conductor using the black and white. Just recode the white with black tape or a magic marker.

Here is the manual: https://dl.dropboxusercontent.com/u/8010163/Bunn_Coffee_Maker_S%2CSA%2CST%2CSTA%2CSTF%2CSTFA.p df
Also you need this: https://dl.dropboxusercontent.com/u/8010163/How%20to%20use%20Test%20Equipment%20Service%20Manu al.pdf
Never try to wire this without following the procedures in the manual. This is necessary because some commercial buildings have 3-phase delta electrical service and it has three hot wires coming in, but one is a high leg at 200 volts which will tear up any equipment using it if it single phase. Other, newer buildings usually have a "Wye" electrical service with three 120 volt legs to ground and 240 across any two legs. You will not know unless you test the service. Never, ever hook up something without testing the voltage on the wires you will use. That model can use 120 volt service or 240 volt service at 20 amps. You have to test the wiring to make sure that neither hot wire is 200 volts to ground as this tears up equipment in two ways: (1) It's too much voltage for device, (2) 200 volts is too much voltage for the insulation and switches in appliance and power will arc to ground (You can see it at times because it looks like little lightning bolts. Very dangerous and destructive.). Always check all the equipment in your restaurant if you have delta service to make sure nothing is on a high leg except three-phase air conditioning/refrigeration units. You should get a good digital clamp meter like the Commercial Electric model MS2002 found at: Commercial Electric Digital Clamp Meter-MS2002 at The Home Depot (http://www.homedepot.com/p/Commercial-Electric-Digital-Clamp-Meter-MS2002/202353289) for $42.38 plus any taxes. You will see on page 36 of the Bunn manual that your model should use 240 volts, but check it out before applying power.