I am trying to replace my old robertshaw thermostat which an honeywell, the problem is from my wall there is only two cables coming out blue and white, there are two letters too close to a wire and all the videos and manuals how to install it shows four it is confusing . We have heater but no cooling system. T

I am trying to replace my old robertshaw thermostat which an honeywell, the problem is from my wall there is only two cables coming out blue and white, there are two letters too close to a wire and all the videos and manuals how to install it shows four it is confusing . We have heater but no cooling system. t

Usually a two wire heat only circuit uses W and R on the thermostat.