Yes you need the cord.
Putting a timer on the controller itself, where you are turning off the controller at night, is not the best way to achieve a night-time drop (NTD). You don't want the controller off, you want the setpoint changed at night. The NTD cord and household timer enables the setpoint change, and that is much more desireable.
>>I am getting a proportional thermostat and saw that you have to buy a cord to attach to a timer for the night drop. Do I need to get that or can I just attach a timer to the unit since it stores the temps? If not,then I will buy the night drop cord.
>>Thanks
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Mark