Honeywell t822d 1255 replacement wiring

[Dee0011]

Hello i have three zone heating to an oil burning boiler only the middle zone thermostat will fire up the system, i was thinlking my thermostat was bad so i purchase a new thermostat to replace my bottom zone thermostat it a honeywell T822D 1255 only two wires are attach to this termostat a red and white but the thermostat does not have r or rh marked on the back so i dont know which is which ..... Any help would be appricated