Thermostat Replacement with PID/SSR

[Mackey1981]

Gentlemen,

I have been a longtime lurker on the forums and really do not like posting to forums to build my post count, only comments that add to the knowledgebase.

I purchased a freezer from CL and want to replace the thermostat with a PID/SSR. I had it set up as a simple on/off control but I want to the fans and light to still function when the compressor is not running. I thought this would be a simple fix, replace the thermostat with the PID/SSR setup and it would work. But once I started drawing out what was happening in the freezer before I started wiring, I could see this was getting well out of my league.

Electronics gurus, I need your help. Below is the current wiring schematic for my freezer and the PID/SSR. I know this has been done countless times, but I cannot figure this one out. Thanks in advance gents. I WILL post the final solution in the form of a wiring schematic.

Rich L.

PID: TET612, JLD612

 

[reynolds5520]

Are you sure about the connections at the compressor?

The way you have it drawn, looks like the compressor will run constantly.

Can you take a picture of the compressor connections?

 

[Mackey1981]

Are you sure about the connections at the compressor?

The way you have it drawn, looks like the compressor will run constantly.

Can you take a picture of the compressor connections?

Reynolds,

Thanks for taking a look at my schematics. The freezer is running properly as it is wired, and the compressor does not run continuously, which is one of the reasons I am not quite sure what is going on and how I would put my PID/SSR into the mix. Here are the pictures of the terminal block on the compressor, the terminal block to the thermostat, and the thermostat. I have a multimeter and can check whatever terminals you think I should to help.

In the first picture, the power from the wall is the bottom cable and attaches to the terminal block on the compressor. The white insulation wire housing the red/white/black/green wire departs the compressor terminal block and connects at the second terminal block in the second picture. The white insulated cable housing white/black/green at the bottom of the picture goes to the thermostat, pictured in picture 3. Thanks again for looking at this, spent the whole day looking at this scratching my head.

 

[IPA-Hole]

That has to be the cleanest CL freezer I've ever seen!

Can't wait to see the finished schematic. Good Luck!

 

[reynolds5520]

Based on what I can see in the photos, it looks like the terminal 2 on your SSR should connect to the compressor at the black wire that runs between the two terminal blocks. It looks like there is a label there, but I can't read it in the picture.


In your schematic drawing, the black wire of the compressor motor should also be shown connecting to terminal 3 of that terminal block. Can you confirm that is where it goes?

 

[Mackey1981]

Reynolds,

There is only one wire connecting to terminal 3 on the compressor, and it is the black wire. The black wire at terminal 3 on the compressor connects to terminal 2 on the second terminal, which connects to the white wire to the thermostat. The black wire on terminal 3 at the compressor/terminal 2 at the other terminal is hot when the compress is not running and is cold when the compressor is running. Also, the little black wire in picture 1 that is surrounded by the ground wire at terminal 1, looks to be connected to a relay on the compressor, it is also hot when the compressor is not running and cold when it is running.

I have no idea where the hot wire that starts the compressor is. It must be in the box behind the compressor terminal block. I can see some wires behind the block in the housing, but I am not sure if I can/need to get at them.

Thanks again for the help.

Rich

 

[reynolds5520]

Yes, the wire that "looks to be connected to a relay" is what is running the compressor. It will be connected to the back side of terminal three.

Terminal three is where you want to connect your SSR output.

In the picture you can see that the terminal strip is labeled L (line) N (neutral) and probably terminal 3 is labeled C for compressor (or maybe thermostat or protector).

Something that may be confusing for you as you test with the meter, you are expecting to see that black wire be hot when the compressor is running and your test shows it isn't. That will be because the white and black of the incoming power cord are reversed. Black should be the L and white the N. You can verify by testing between white and green and between black and green. Black should read hot when tested to green and to white. White should read hot when tested to black but not when tested to green.

It may have been changed by the previous owner, or it may have come from the factory that way. It works, just can be confusing. You will need to swap them for your PID/SSR to work properly - if you power the PID/SSR directly from the incoming black and white wires as you show in your schematic.


If you decide to swap those wires, also test at the light to make sure it is connected correctly at terminal strip 2 - the center pin of the socket should go to L (line), terminal 2 on strip 2 and should be hot (through the door switch).


I found a schematic of your compressor:
www.irepair.com/ipod-video-parts.html

Where the factory schematic shows "SUPPLY" is your N and terminal 3. The relay looking component in picture 1 is the "OVERLOAD" in this factory schematic.



I hope all of this is making sense to you, let me know if anything doesn't.


Kevin

 

[Mackey1981]

Kevin,

That makes perfect sense to me about the wiring from the wall being incorrectly attached to terminal block 1, and I verified this by checking the loads per your instructions; added that to my bag of tricks. I am currently making a new schematic with the fixed wiring before I start disconnecting and reconnecting wires to terminal blocks 1/2. Block 1 will be a simple change of the Red/White wire to line up with the correct positions of the black/white wires from the outlet. The tricky part will be changing the light/fan/thermostat/compressor on block 2, which is just going to take a little time. I was not able to find the schematic at the link you provided, but is the black wire on block 1/terminal 3 supposed to be neutral or hot when I have this wired correctly?

Well after typing that last part, I decided to disconnect the wires entering block 2 just to see what was happening with terminal 3 on block 1. Well now both the wire on terminal 3 and the one on the relay are now Neutral. I hope that is the correct wiring because now I wouldn't be able to connect my SSR output to block 1/terminal 3. It will have to plug in somewhere else. Oh, and the Block 1/Terminal 3 is labeled "1".

Thanks again for the help Kevin.

Here is the picture of the rewired Block 1. Note terminal 3 and black wire on relay are now both Neutral.

 

[Mackey1981]

After a little more work with the multi-meter, I have discovered that block 1/terminal 3 and the relay wire are connected to whatever is connected to the N post on block 1 (terminal 5). I disconnected the black wire at terminal 3 and the relay was still showing voltage when checked with black wire at terminal 4. The same was true when I disconnected the white wire at block 1/terminal 2. I hope that helps some.

Rich

 

[Mackey1981]

Well gents, I have this thing figured out. Bottom line is I do not think it is possible for the PID to truly replace the thermostat. I'm sure the electronics gurus would be able to crack this nut, but I am not able to with only a PID and SSR. The PID/SSR can only be used in an ON/OFF configuration with the SSR supplying power to Block 1/Terminal 5 on my setup. I will cleanup my schematics and post why I do not think this is possible later this week after I finish up on my project. I hope it will help others understand what is happening within this compressor. I am sure the experts out there have already figured this out, but as this is my first real electronics project, I have learned a bunch through trial and error, plus the wonderful threads posted on this site.


Kevin, you were a tremendous help to me and I sincerely appreciate the time you spent helping me with this project. Standby for the updated schematics on my build, I am sure it will look similar to other setups on the forums, but I will try to explain what is happening within Terminal Block 1 on the Compressor and what is happening with the thermostat as the freezer cycles.

Rich

 

[reynolds5520]

I am sure we can get it to work for you.

What is the model number of the freezer. I bet we can find the full schematic.