I have a Paragon 8145-20 D-frost-O-matic Time control installed in my walk-in freezer, how can I increase the time for derost. Now It runs for 11 minutes then stop for 3.5 minutes. I think 3.5 minutes of stopping is not long enough to defrost so the ice accumulated alot causing the freezer not cold enough.

http://waterheatertimer.org/Paragon-timers-and-manuals.html#defrost
Link has infromation about paragon 8145-20 240 volt timer
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1) Copy following links:
http://waterheatertimer.org/images/8145-work-image.jpg
http://waterheatertimer.org/Paragon-timers-and-manuals.html#defrost

2) Typically the 8145-20 defrost cycle is time-initiated and starts when tripper pin located on outer part of dial passes the time-of-day point.
Defrost cycle terminates or ends when pressure or temperature switch activates. This is also called the cycle limit switch.
http://waterheatertimer.org/images/8145-20-wiring-600.jpg

3) So your situation sounds like the pressure or temperature switch is not working correctly.

4) The 8145 timer also has 'time termination' setting. This red tripper is located on inner part of dial.
Usually the 'time termination' is used as back-up system if the pressure or temperature switch fails so that defrost cycle will not continue melting everything in freezer.

5) To solve problem until pressure-temperature switch is replaced, you can disconnect wire on terminal X, and then set 'time termination' for correct length of time by experimenting.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

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Abrir enlace en internet:
http://waterheatertimer.org/Paragon-timers-and-manuals.html#defrost

is it a Refr. or a Freezer for mthe freezer you can use a paragon model 8141-00-oem D-frost-o-matic timer control................good luck

Open following link to see wiring diagram and manual for Paragon defrost timers:
8145-20 is 240V time-initiated, pressure or temperature terminated, with back-up time termination.
http://waterheatertimer.org/Paragon-timers-and-manuals.html#defrost

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The adaptive derost control has gone bad a very common issue. It will work a couple of weeks before its back to its frosting over. It just plugs in but to get to it you must remove the controls at top of frigde section in the back right corner held in by two scewrs.

If the air flow and temperature are not being compromised leave it alone. If there is a gradual build up of ice on the evaporator you may have a defrost element or defrost limit switch problem. Set the defrost duration duration to 45 minutes and see if that solves the icing problem. 4 defrost cycles a day should be enough to keep the icing problem at bay. 3 defrost cycles at night about 1 hour apart may also remedy the problem. Experiment until you find the right combination of defrost cycles for your freezer. Watch for any thawing of the product in the freezer and adjust accordingly.
Bills Refrigeration/Montana.

Thanks for the question It looks like you have a no derost problem Open freezer door and reach in to the backwall if you feel a lot of frost build up you have a no defrostproblem check to see if the fan in freezer is running if not replace fan if the frost is there you could have a fefrost timer problem thanks for the question the appliance doc

Thanks for the question When this happens if the evaporator is all frosted up you have a derost problem could be your timer or your defrost thermostat which is located on the coils of the evaporator you can check this with a volt meter these meters are cheap you dont need a very expensive for ahout 20 dollars or the defrost timer one of the two is your problem thanks for the question The appliancedoc