Help bypassing beverage chiller thermostat

[ahung12]

I've seen a bunch of members already helped out with this similar issue, so I'm looking for the same guidance but on my specific application. The chiller is an IDW GS-4, and I need it to cool down to ~35 degrees F. It can only get as low as 44 degrees even after setting the coarse adjustment screw to the lowest setting. I suspect that the chiller's internal thermostat has set the lowest temp to be around that 44*, so I'm looking for a way to bypass it and I have an ITC-308 on the way.

I've yet to disassemble the thermostat box, but I've uploaded a copy of the circuit diagram for this chiller. Based on this, would anyone be able to tell me what sort of wiring changes I'd need to make in order to bypass the thermostat, while keeping the LED lighting functional? Is the ITC-1000 a better choice given I may need to cut/splice/junction wires?

If a picture of the opened-up thermostat box is needed, I'll throw one up. Thanks.

 

[day_trippr]

Welcome to HBT!


If you remove the wires on either side of the SAT block (which is the thermostat) and run those same two wires through the "Cool" relay, the ITC-308 will control the compressor and the condenser fan properly while allowing the door switch (and the manual light switch) to operate the LEDs even when the compressor is not enabled by the ITC.

Somewhat interesting, it appears the evap fan runs 24/7. Does that fit your observations?

Cheers!

 

[ahung12]

Thank you kind sir! I was hoping you'd respond, I've seen your advice pop up countless times in the other threads. Will take a peek at the actual thermostat tomorrow to make sure I'm properly ID'ing the wires, and will throw up photos to double check if you don't mind.

 

[day_trippr]

Feel free to follow-up in your thread, the HBT community is here to help where we can

Note there will likely be a green or green/yellow striped wire connecting the shell of the thermostat to the chassis. You can leave that in place. The two wires in/out of the thermostat are what you're interested in and will be some other colors...

Cheers!

 

[ahung12]

Edit: I'm a doof . Yes, the evaporator fan is constantly running. I did indeed have it mixed up with the condenser fan.

Regarding the ground: I'm planning on splicing on a 3 prong extension cable. Should I hook up the ground in the extension to the chassis in the same point as the tstat's ground? Or is a 3 prong not necessary?

Here is the thermostat wiring, and my assumptions/questions:

1. Temp probe (it snakes up into the back of the unit, into an inaccessible panel with sealant around the opening)
2. Neutral
3. Hot - why are there two wires coming out? When splicing, do I splice them both into the extension plug?
4. Ground for the neutral, which goes into a mess of wires that bundle up around the overload protector/compressor.
-Not pictured is a separate ground for the thermostat directly onto its metal bracket itself. Its on the opposite side of the hot/neutral connectors.

Also, fun times - the compressor is short cycling. On for maybe 30 seconds, then off for minutes. And the manufacturer tells me the temperature floor of these units is ~38 - 42* F.

What's odd are a few things:
1. The unit itself appeared nearly new when I took ownership. The shelves were still zip-tied onto their brackets and the side railing. While there are scuff marks and a small amount of dust around the unit, overall it appears to be in very good condition and barely used. Could I be that unlucky as to score one that came from the factory with a bad compressor/starter relay/overload protector/gas pressure/etc?
2. Despite the short cycling, the unit still produces cold air and was able to hit 41.5* F in about 3 hours of running, and seems to maintain that temp even with the very short compressor cycling. The condenser coils are not getting hot, only very slightly warm, and the compressor itself is not warm at all. I hear a "click" when the compressor shuts off, but I'm not sure what the overload click sounds like vs. starter relay click. So if there is a problem, I'm not sure if its the overload, the compressor, the starter relay or some combo of all.

I'm committed to hooking up the ITC-308 once it arrives and see if I can still force the unit to maintain <38* F.

 

[day_trippr]

Note according to the diagram there are two fans on board: the evaporator fan and the condenser fan. The former does not appear to have any control, while the latter comes on with the compressor.

Next...there is no "neutral" on the thermostat. There's a hot in and a switched hot out. Neutral will be found at the compressor.
The double-crimped black wire is either the hot in or the switched out; the single-crimped black wire is either the switched out or the hot in. Those are the two connections you would run through the Inkbird "Cool" relay, and it doesn't matter which wire goes on which side of the relay.

The green wire attached to the shell of the thermostat is the safety ground and should end up connected to the chassis somewhere. Yes, you want to use a 3-prong plug and wire the ground lug to the chassis or any of the green ground wires.

Can't comment on the short cycling or the clicking. When was the last time the fridge was used?

Cheers!

 

[ahung12]

Ah good, that makes things easier.

I don't think the fridge was ever used on a constant basis. Probably just plugged in and run for testing. The shelves were all zip tied to their brackets and side railings as they were from the factory.

 

[day_trippr]

Something I would try: unplug the unit from the wall outlet, remove the hot-in and switched-out wires from the thermostat, connect them together, and plug the unit back into the wall outlet. Let it run at least long enough to see if the short-cycling changes at all...

Cheers!

 

[ahung12]

Aha yes, I've seen this as the permanent bypass method suggested to others. It should basically turn the thing into a freezer if the cooling system is working properly, right?

I will give it a shot tomorrow.

 

[day_trippr]

Jumpering the thermostat out allows running the whole thing by switching the line cord with an external controller without worrying about the oem thermostat getting in the way of things.

In your case, as you wanted to keep the interior lighting functional you can't go that route. Hence wiring the controller to switch just the compressor/condenser fan by replacing the function of thermostat.

But I'm suggesting bypassing the thermostat temporarily to see if the short-cycling is resolved. If nothing changes, the overload switch might bear testing next...

Cheers!

 

[ahung12]

Dumb question: other than retaining the functioning of the lights, what is the difference between using the temp controller the "traditional" way (plugging in) vs. jumpering the wires? Either way, aren't I bypassing the stock thermostat and letting the temp controller and it's thermostat activate the compressor?

I've currently got the fridge plugged into the temp controller with all settings dialed in, and the issue is the same. Compressor cycles on for about 1 minute, then clicks off. Target temp is set at 36* but the compressor stops before its even remotely close. Condenser lines are getting slightly warm to the touch, the compressor is not warm at all.

 

[day_trippr]

Again, the primary difference is whether interior lights still work (your case) or not (conventional usage model). But the conventional model has a caveat: with the original thermostat in place it will dictate the coldest temperature. Which was a problem in your case.

Something is definitely amiss with your fridge, it should not behave like that. If you have an AC voltmeter, when the compressor turns off, check the voltage on both sides of the overload switch. If the line side is hot (120vac) but the compressor side is cold (0vac) then something is tripping the overload switch...

Cheers!

 

[ahung12]

Makes sense now. I went ahead and jumpered the wires, and hey presto the fridge is "working". Multimeter is at the office, and I'll be traveling through the end of the week and so I will of course be a miserable mess until I get back and am able to properly test things.

Here's my concern now: the fridge is running and responding to the temp controller, but this is obviously a band-aid for a more serious issue.

1. If that issue is a faulty overload protector, than in the event that the overload protector is actually needed, what would happen? The compressor just quits/locks up? Or some sort of thermal runaway event?
2. If the issue is low refrigerant, same question - what happens? Just no more cooling? Or worse?

 

[day_trippr]

If you could clarify "jumpering the wires" that would be helpful from here, as I've provided at least two different "jumpering" schemes with quite different topologies...

Cheers!

 

[ahung12]

I joined the two wires together, didn't touch the ground. But still running the fridge's power cable into the external temp controller, which is plugged into the wall outlet.

 

[day_trippr]

Ok, that's encouraging as it fingers something fairly trivial (thermostat behavior) vs something sinister (overload tripping).

So here's a theory: you've been doing all of this with an empty fridge, yes?
Is it possible the cabinet interior is chilling so quickly to the limit of the oem thermostat that it appears to be short-cycling?

In any case, you can pick whatever solution you like: either route the thermostat wires through the Cool relay on your controller and leave the fridge line cord plugged into the wall (interior lights work properly) or leave your current setup as is and just control everything with the Inkbird (interior lights won't work when the Inkbird isn't in Cool mode)...

Cheers!

 

[ahung12]

Sorry for the long delay, but I did want to come back and thank you for your help! Everything is running perfectly at this point.

But to go back to your question: Correct, all my testing I did with an empty fridge and I did consider that what appeared to be short-cycling might simply be as you state - lack of thermal mass to regulate the temps and causing the entire system to function as designed, but at a rapidly sped up pace.

I'm actually using this for dry-aging beef, and once this run is completed I'm going to be hard-wiring per the second route you suggested. That is, route just the thermostat wires through my temp controller and run the fridge's power cord to the wall, in order to keep lights functioning when I want them.

Thanks again!

 

[day_trippr]

Happy to have helped and your kit is running well

 

[ahung12]

I finally got around to hard-wiring the thermostat lines to a separate power cord, but something appears to be wrong.

I used a three-prong power cord to join to the hot in and switched out wires, and connected the green wire of the power cord to the chassis of the fridge. I didn't make a note of which of the power plug's wires went to the hot in and switched out wires. The power cord is plugged into the Inkbird temp controller, which itself is plugged directly to the wall outlet.

The fridge's power cord is connected directly to the wall outlet.

The fridge will power on, and evap fan is constantly running. The lights will power on/off. However, the compressor will not turn on, and the fridge is not getting cold. I have the Inkbird set correctly (no compressor delay, target temp 35 with +/- 2) and the internal fridge temp is 67.

Something odd also happens: If I leave the fridge's power cord plugged into the wall outlet but unplug the Inkbird from the wall outlet, the Inkbird continues to get power. I can even go through and change settings, as if it were still plugged in and it will remain that way until I unplug the fridge's power cord.

What have I messed up? Diagram if it helps.