Inkbird STC-1000 with Solid State Relay on a Keezer Help.

[steveperry]

My STC-1000 has apparently failed and allowed the compressor to continuously run on my keezer driving the temperature to -28F.

Replacing the thermostat is easy enough, but through some research I have read that adding a Solid State Relay (SSR) can help prevent the thermostat from failing again.

I'm not sure what kind of SSR I would need.

Will this work? GEREE 24V-380V 40A 250V SSR-40 DA Solid State Relay Module

I will have to buy some additional wiring as well. What gauge should I buy? (The keezer is at a friends or else I would have the answer)

The freezer in use is a GE 5.0cf FCM5SUWW

Here is a wiring diagram that I drew up. If it is wrong, can someone point me in the right direction. Or confirm that it is correct. Any other tips are helpful as well.

 

[Schreiner]

I'm chiming in more to learn from others than being able to offer solid help.

It sounds like, to me, your STC-1000 is faulty.

That small freezer shouldn't pull more than the 10 amp maximum that the STC-1000 is rated for. If your freezer is pulling over 10amps then an SSR could protect the STC.

 

[steveperry]

I'm chiming in more to learn from others than being able to offer solid help.

It sounds like, to me, your STC-1000 is faulty.

That small freezer shouldn't pull more than the 10 amp maximum that the STC-1000 is rated for. If your freezer is pulling over 10amps then an SSR could protect the STC.

Ya, the thermostat definitely failed, it had been running fine for 8/9 months. If the freezer shouldn't be pulling enough amps to require an SSR then i'll just replace the thermostat and do the SSR if it fails again.

Thanks for the input.

 

[steveperry]

I have also seen this wiring diagram. (I most likely used this one with the neutrals in the thermostat relay because that is how it is diagrammed in the instructions)

Is one better/safer than the other or does it matter?

 

[day_trippr]

Neither of those schemes will work given the specified SSR.
SSRs need a DC signal across the control inputs to switch the SSR.
Connecting them to an AC source will likely toast them.

As well, it's never advisable to slave an SSR to a controlled relay due to the relay point bounce wreaking havoc on the SSR...


Cheers!

 

[steveperry]

Neither of those schemes will work given the specified SSR.
SSRs need a DC signal across the control inputs to switch the SSR.
Connecting them to an AC source will likely toast them.

As well, it's never advisable to slave an SSR to a controlled relay due to the relay point bounce wreaking havoc on the SSR...

So this?

or this?

 

[day_trippr]

Nope. Leaving aside the premise of controlling any SSR with a relay, both of those diagrams are just iteration of the same basic problem: there's no switched DC controlling the SSR in either scheme.

If one was determined, one could add a 12V wall wart to the drawing, connects its AC hot and neutral to the incoming AC line, route the hot side DC output through the Cool relay and use the relay output as the "+" control input, with the "-" control input connected to the return side of the wall wart output.

But...after all that, you'd still have that point bounce to consider....

Cheers!

 

[sc300ftw]

so i just cut the factory power cord and used the stc1000 with an extension cord to cut the power on or off and then just turned the freezer to max cold. its held temp and cycled on and off perfectly for a month or 2 now. is this not what most people do ?

 

[day_trippr]

That is indeed what most folks do...

Cheers!

 

[kristiismean]

Here is what I did with mine.

 

[Krazykamper]

My STC-1000 has apparently failed and allowed the compressor to continuously run on my keezer driving the temperature to -28F.

Replacing the thermostat is easy enough, but through some research I have read that adding a Solid State Relay (SSR) can help prevent the thermostat from failing again.

I'm not sure what kind of SSR I would need.

Will this work? GEREE 24V-380V 40A 250V SSR-40 DA Solid State Relay Module

I will have to buy some additional wiring as well. What gauge should I buy? (The keezer is at a friends or else I would have the answer)

The freezer in use is a GE 5.0cf FCM5SUWW

Here is a wiring diagram that I drew up. If it is wrong, can someone point me in the right direction. Or confirm that it is correct. Any other tips are helpful as well.
View attachment 553996

Make sure you get an AC AC SSR. Think of the connections as a switch. You will be using the freezers hot (black) wire as the interupt. This is on one side of relay Current in from plug to current out to freezer. That is the easy part. The controlled side is going to be the hot from your controller and a neutral.

The controller doesn't need ground so take a regular extension cord. Cut and strip. Forget green wire all together. Take a bit of the black to make 3 jumpers. One goes in controller unit power 2nd goes in cooling in. Wirenut both of them to the black in extension cord. The third one goes on cooling out and to the SSR . Now for white wires one jumper goes into control unit power, 2nd from the out on the SSR. Wirenut these to the white on extension cord. Plug in and there you have it.

The main reason for the SSR is the amp draw is reduced from the controller. Appliance motors and compressors are dirty when using electricity. Even though the controller is stated to take 10 amps... You never reduce an amp draw and then open it again. Be safe and spend $10 bucks to protect your investment by putting relays and or fuses in. By not using the SSR you are reducing the appliances ability to use the right size wire to get what it needs. Its better to interupt the same power line with the same if,not higher relay amperage then to reroute and splice and tamper with it.

Hope that makes more sense. All else fails I can try and draw you a diagram. Yours are utilizing one power line. You need two lines to play safe.

For those of you that aren't quite sure... Don't say this is what I did and it works. Electricity is not something to mess with wrong advice. How would you feel finding out there house burned down because your advice of that's what everyone else does doesn't apply to their situation.

 

[Krazykamper]

This gives you idea, just run controller on its own power source.

 

[BullGator]

So that's an AC-AC SSR and if I have a 2 stage temp controller I would need 2 of them correct? That is, if both my heating and cooling source will be pulling over 10A?

I purchsed a DC-AC SSR and I think I may have got the wrong kind. Not sure how to wire that one. I read I may need an external power source which I think is as simple as an old phone charger, but I still do not know exactly how to wire it. It looks like an AC-AC SSR can be wired pretty simple.

 

[day_trippr]

Going back to my earlier post, you can use the DC output of a cheap wall wart to energize a pair of SSRs via the controller's Heat and Cool relays. Run the positive DC voltage to the inputs of both relays, take the Heat relay output to the positive terminal of the
"heat" SSR control inputs and the Cold relay output to the positive terminal of the "cool" SSR controls, then connect the negative terminals of the two SSR's control inputs to the DC return side of the wall wart.

Done and done. BUT, using a relay to switch an SSR is sub-optimal as relay points bounce and every bounce switches the SSR controls. If faced with this as the only viable solution I would add a wicked slow low-pass filter (basically a low ohmage resistor between relay and SSR positive control input with a big honking capacitor from the SSR positive control input to ground) to try to filter out the bouncing...

Cheers!