Nice compact surface-mount timer module FOR THE PRICE:Size 1.25" x 2 3/8" x 2 3/8."3 Complaints: Buttons are boggy and often have to be pushed more than once to get a response. The manual shows countdown feature 1sec-99minutes plus timer display shows seconds, but this is evidently not a usable feature for on-off function because the manual shows no way to program countdown and no experimentation with buttons reveals method to activate countdown for on-off function. Manual shows pulse function 1-59 minutes but manual shows no method for setting the pulse feature.However the features and price make up for complaints. For example this timer is rated for 120 volt, but other models in the CN series are available for wide variety of voltages, 12 and 24 Volt AC-DC etc.Buy 2 for this price, and they still cost less than other timer modules.No timer module on the market today is immune to surge... so install surge protector and inline fuseFeatures of CN101ASimple programming steps. Will be able to figure ti out if you lose manual.1 to 17 programs. Up to 17 on-off programs per 7-day week, or repeat same programming each day.1 minute minimum set time.24 hour clock format.To remove a preset program: Can set programming to 0:00 to delete individual program without having to delete all programming.Reset button to clear all programming.Three year power carryover. Will not lose programming or current time.-10 to +40 degrees C temperature rangeThis is the A series timer and has 4 terminal connections on back of timer, two terminals marked Power and two terminals marked Switch.Switch is Normally Open or NO/ which means timer must turn ON for switch to be ON(Contrast the A series with the B series that has both Normally Open NO plus Normally Closed NC switch terminals.)Rated 8 amp at 120 volt/ 5 amp inductive motor loadWiring:Connect 120 Volt Hot and Neutral to Power terminals.The Switch terminals are 'dry' and have no power until you connect wires.Run jumper wire from Hot to one of the Switch terminals.Your Load will have Hot and Neutral: Run Load Hot to second switch terminal, run Load Neutral and connect to other Neutral.Wiring and manual posted on following link/ including other timer modules:http://waterheatertimer.org/Programmable.html#PB