I'm replacing a 23 year old manual Honeywell thermostat with a new digital Honeywell thermostat model RTH111. The old thermostat has two wires (colors white and red) but no designation on the terminals. This is for a hot water baseboard gas fired boiler.

Which terminals do these unmarked wires connect to on the RTH111? The terminals are marked O/B, Y, RC, R, G, W

Thanks,

Roy

R and W,
Turn off power/breaker,to boiler before installing, then back on


Just wondering if the old honeywell still working, why change it