The Mystery of Timers and Photocells

There are two main reasons why your lights may not be turning on and off at the original programmed times.

  • Your timer may need to be adjusted for daylight savings time
  • Your timer may be incorrectly programmed

Daylight Savings Time

(See below for pictures)

If you have an Intermatic SS8, Intermatic ST01 Timer (See below for pictures) then the daylight savings adjustment happens automatically.

The K-15558 plug in timer, located in the Transformer has a manual daylight savings time adjustment. The screen should display an ‘S’ during daylight savings time and the ‘S’ will disappear during the winter period. To make an adjustment, look for the HOURS and MIN buttons and press them simultaneously.

The Leviton 1122 in wall timer must be reset to the correct time of day. Press and hold the lower right hand button until the black dot on the screen moves to the correct time. *This timer utilizes half hour time blocks

The TN811C Clamshell plug in timer must be reset to the correct time of day, by turning the dial clockwise and adjusting the pins.

Re-programming your Timer

If your timer has been adjusted for daylight savings time (see above), but still shows the incorrect time of day you may need to reprogram your timer. In order to do this, click on your timer picture and follow the directions in the manual.

Intermatic SS8

Intermatic ST01


Leviton 1122


Before programming your timer please also read this brief explanation about how timers and photocells work together.

In most automatic scenarios we use timers and photocells in combination. The timer may be inside (on the wall), or outside (in the transformer). The timer is used to control the power going to the photocell, and then to the lights. Usually the timer is set for 4:00 p.m. This is the earliest time that it could get dark. When it reaches that time, energy is supplied to the photocell. The photocell reacts to sunlight and will allow the lights to come on when it gets dark.

Having the lights come on only at sundown is extremely beneficial in lengthening lamp life.

The timer will turn everything off at the hour determined by you.

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