I have an existing old Homart thermostat for a old gas furnace. Only 2 wires enter the thermosat. I purchased a Honeywell RTH2510 programmable thermostat that seems to need more than 2 wires. Can this be used on my system and how to hook it up?

Follow the directions in the thermostat box. All you need to connect is the R terminal to one wire and the W terminal to the other wire. Install batterys and follow the setup schedule.

http://customer.honeywell.com/techlit/pdf/PackedLit/69-2381ES.pdf

http://customer.honeywell.com/techlit/pdf/PackedLit/69-2380ES.pdf