Custom controller for Whirlpool FP313 ELT

[Harshana]

Hi all,

I bought a Whirlpool Protton 3door refrigerator (FP313 ELT) last May. I was replacing a 20yr old Sisil refrigerator still in working condition, but it was old. New fridge controller got fried in less than a week, it was replaced free as it was under warranty. Last November also the controller got fried. This too it was replaced after calling many times to the local agent. Weeks after it got fried again, clearly I should be having lot of electrical spikes. However, none of my other equipments TV, DVD player, washing machine, computer etc are not effected, but only the fridge burns. So I figured its bad supply and bad controller design.

When I closely looked at my controller cct, I realized they have simply used a cheap RC circuit to drop 240V to 5v and using it to run the PIC 16Fxxx uController. Obviously, any electrical spike large enough to jump through the capacitor will hit the ucontroller with high voltage.

Ignoring the offer by the agent to return the refrigerator and go for a new model, I decided to build my own controller.

So I made a simple cct with a uController that reads the temperature from the two thermistors and switch on and off the compressor. With little bit of experimenting, I realize that I should leave the compressor off at least for 5 minutes between each run.. If not, there's risk of compressor being switched off from the protection switch at the compressor.
I think when the compressor runs for sometime, then there's pressure built up at the output. When stopped, we need to keep it for sometime till the pressure drops. If I start the compressor too soon, It will not be able to start-up and it gets stuck, so the protection switch goes off.
So far, I have better power consumption than with the original controller (roughly 1kWh / day, freezer @ -12C).

My question is : Does the min off time depends on the amount of time the compressor runs. Eg. Running the compressor for 5minutes should have 5minute off time and if I run it for 2minutes, will the min off time drops ?

I have attached a wiring diagram with little bit of additional information.

Thanks,
Harshana

PS: To the admin. Please make docx also a valid file format.

[Tesla]

Hi Harshana and welcome to the forum
The minimum off time is rated by how many starts per hour the compressor motor can handle. You will have a motor that requires the pressures to equalise before starting. This gives things inside time to cool down a little before starting again. So there needs control for minimum time to start after stop - delay on and a limit of how many starts per hour. For a larger appliance (chiller) had a rate of 5 starts per hour so I set the delay on timer for 20 minutes incase the compressor started and run for only one minute or so. If you run for one minute or 10 minutes the delay time should be a minumum of x minutes regardless of the time it has been running for. Check the name plate of compressor and search on the model for compressor data to find max starts per hour.

[Harshana]

Thanks Tesla for the quick response.
As per my software (firmware), It can't cycle below 6.5 minutes (ie, 1.5min running and 5 minutes off). But I have seen cycle averaging between 7~7.5 minutes and going up to 8.5 at night.

I have built bit of intelligence on deciding the ON time (between 1.5-5 minutes) and sometimes OFF time goes beyond 5min. (minimum 5min or till temperature goes to max allowable). Which means my starts should be always below 9.2/hr, averaging between 8.5~8/hr and 7/hr at night. I will see what the spec sheet says about starts/hr for my compressor

Thank you again.
Harshana

[Tesla]

Realistically I would think the
(minimum 5min or till temperature goes to max allowable)
should be more like
(minimum 5min and till temperature goes to max allowable)
This would give 20 starts per hour but could be adjusted to suit starts. Then a little time could be added to account for the function of a door opening, even incorporating the door open switch.

[Harshana]

You are correct on the interpretation of my "minimum 5min or till temperature goes to max allowable", sorry about that.
So it will not start for 5mints for sure. If the cool is there, it will stay longer in OFF. My worst case cycles go as 1.5 ON - 5 OFF - 1.5 ON - 5 OFF - 1.5 ON - 5 OFF - ... So maximum 60/6.5=9.2 starts per hr. not 20 per hr. Let me know if I misunderstood the starts/hr calculation.

When calculating the ON time, if the cool drops before 5mints, my next ON time will be 30secnds longer (starting at end of 5mints). If the cool keep longer than 5mints (more than 310seconds), I reduce the next ON time by 30 seconds. This way ON time can go up and down between 1.5mints and 5mints limits.

Hope this is clear.

[Harshana]

Hi all,

My compressor is ADW66A. I can't seem to find the number of starts per hour for this on web. Can someone help me with this?

http://sporlan.en.alibaba.com/produc...frigerant.html

Thanks,
Harshana

[Tesla]

You could use this general guide http://www.joliettech.com/allowable_...-intervals.htm or email the manufacturer.