We install the timer and it does not work automatically. We can switch it on only manually

This timer is rated for incandescent light bulb only.
With 40 watt minimum.
With 100' maximum distance between bulb and timer.
http://waterheatertimer.org/Intermatic-timers-and-manuals.html#ej351

EJ351 is not rated for CFL bulbs (or motors etc).
CFL bulbs are considered inductive loads (same as motors), while incandescent bulb is resistive load (same as a heating element).
Both types of loads use electricity differently.
Programmable wall timers are not ordinary on-off switch... unless you use the override switch.
... instead timers control electricity with electronic circuit board.
So when the manufacturer designs the electronics inside the timer, the design must anticipate how the electricity is used by the load.
Older designs like EJ351, and some modern timers, are not rated for CFL.
... however most newer timer designs are rated for both resistive and inductive loads.
Always read the specification sheet for load rating before installing programmable timer.

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You have line and load wires reversed on single-pole timer
Timer has black and red wires... switch connections with each other
http://waterheatertimer.org/How-to-wire-timers.html

Gene

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Something doesn't sound right.
I have two of these timers and cannot figure out what your timer is doing, unless wiring is wrong or timer is defective, or you connected timer to 3-way switch.

15070 is single pole analog timer that requires neutral wire.
Slide switch is set to 'Timer' for automatic timer functions.

Open following links to identify timer and see wiring and how to set analog timers:
http://waterheatertimer.org/GE-timers-and-manuals.html#15070
http://waterheatertimer.org/images/GE-15070-wiring-1-500.jpg
http://waterheatertimer.org/How-to-set-timers.html
http://waterheatertimer.org/images/Woods-59017-mechanical-timer-300.jpg
http://waterheatertimer.org/Woods-timers-and-manuals.html#59017

If manual override works, and dial rotates on time each 24-hours, then worn trippers are suspect.
http://waterheatertimer.org/Intermatic-trippers-and-parts.html#sprinkler
http://waterheatertimer.org/How-to-troubleshoot-Intermatic-timer.html

Upvote the help.
And take advantage of fixya expert assistance live.
For a price, expert works with you while you work on timer or any do-it-yourself project.
Fixya is always less expensive than a service call.

Sounds like the drive inside the timer switch. There is a timer motor that causes the timer switch to progress through the stages. When you manually progress the timer, it is physically turned to the next position and the switches all work as designed; it's just that the motor is incapable of doing that job for you as it should.
You need a new timer.

A) GE 15069 image at Amazon
http://www.amazon.com/60-minute-Automatic-Shut-Off-Timer-Switch/dp/B002DNAE7Q

15069 manual
http://www.jascoproducts.com/support/manual-downloads/applications/DocumentLibraryManager/upload/In-Wall-15069-Manual-eng.pdf

Manual shows GE 15069 countdown timer is rated up to 1/2 horsepower
Whole house fan is likely 3/4 horsepower >> check nameplate on fan motor.

B) work around:
Hook timer up to a contactor/relay.
Timer turns on 120 volt, 7 watt contactor coil.
Contactor turns on fan motor
http://waterheatertimer.org/H230A.html
Square D contactor at Grainger
http://www.grainger.com/Grainger/SQUARE-D-Compact-Contactor-5B132?Pid=search
http://www.pexsupply.com/Furnas-Controls-45EG20AF-2-Pole-30-Amp-120V-Contactor
I buy these contactors at local HVAC supply for $15
add a comment if you need help wiring this device.

C) List below shows countdown timers with horsepower rating:
GE15088 countdown timer is rated 3/4 hp
http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay

Intermatic spring wound countdown timers are rated for 2 horsepower
http://www.intermatic.com/products/timers/in-wall%20timers/decorator%20spring%20wound%20timers.aspx

Woods spring-wound countdown timer says bath/ ceiling fans, but doesn't give horsepower
http://waterheatertimer.org/pdf/Wood-59700-series--spring-wound.pdf
http://waterheatertimer.org/Woods-timers-and-manuals.html#countdown

Woods push-button countdown is 1/4 horsepower
http://www.amazon.com/Woods-59014-Decora-12-8-4-2-12-Hour/dp/B002C54GH4

Lutron MA-T51 countdown timer specifically says it cannot be used for motors, which says the electronics inside each device is Load specific
http://www.amazon.com/Lutron-MA-T51-WH-Maestro-Countdown-Timer/dp/B001EFV1DA
http://www.lutron.com/TechnicalDocumentLibrary/0301041A.pdf

Pass and Seymour RT1 countdown does not show rating for horsepower, so this timer will probably not work for fan motor
http://www.homedepot.com/Electrical/h_d1/N-5yc1vZ1xg8Zarcd/

Wattstopper RT50 at Grainger shows 1/6 horsepower rating
http://www.grainger.com/Grainger/WATT-STOPPER-Time-Switch-2HTE1?Pid=search

The Grasslin analog timer works same as GE 15070
http://waterheatertimer.org/GE-timers-and-manuals.html#15070

You can also download Grasslin manual:
http://www.intermatic.com/products/grasslin/electromechanical%20timers%20and%20timer%20modules/in-wall%20timers.aspx

If you can also manually turn the dial so that the load turns ON and OFF, then the timer motor is bad :-( Replacements are available here for about $30:
http://www.aplussupply.com/intermatic/timer.htm
Scroll down to "WG 1573", Timer motor 208-277"

Did you mix up the pointers? One of them is for off and one for on. Dont know any other reason. If the timer is working all the pointers do is manually trip the lever as it comes past. On and Off should be stamped on the pointer.

switch to malfunction YES HOMEDEPOT SELLS A ON OFF SCREW KIT CHEAP..VOTE..JAY