We purchased a wall heater thinking the directions said it could be wired either 220 or 110 but when my husband started to install it he found that was not the case. It was special ordered from one of the big box stores and they won't allow a return. Any help?

If it said 220v or 110v there should be a wiring diagram for this in the unit or the box or there might be labeled connections on the units terminals.

If it is convertible then you can do it. If not then no, there is no way to make this work.

The voltage rating is on the label and in the instructions of the unit.

If only 240 volts, will need to install a 240 volt circuit with the rated amps for the unit.

If you provided the make and model number of the heater, perhaps we could help more.