I have two unmarked wires leading from my thermostat to the furnace(gas fired steam).How do I set up the wires with the labels listed as: o/b,y,r and g,w? Thanks in advance for any information. New thermostat is a Honeywell RTH2300B which is a 5/2 day programmable thermostat.

Honetwell code for their letters on their web site says Rh is hot wire to heater and W is heat relay or neutral. In any case it's ac in a remote circuit so it doesn't matter which ( Rh or W gets which wire) Just went through the same hassle myself with little help from other web sites. So one wire to Rh and one to W.