regulating my DIY water chiller fro dehumidifier

Hello all you DIY'rs.
I am running some test on a diy water chiller I am trying to put together.
I have a whirlpool dehumidifier I got for free. I disassembled the dehumidifier and separated the cool coil and moved it up and forward and in a 18 gallon tote. I filled the tote with about 9 gallons on water. (My rdwc syatem is a total of 10 to 11 gallons.)
I sat this baby in my water that was 76 degrees for about 1 hour and the temp dropped to about 46. INSANE.
The bottom half of the cool coil that was submerged started to build a layer of ice over the coils submerged in water.
I love how well it works but I dont want to come home from work and find my rez frozen.
I am thinking i need to set up a thermostat that will regulate the power on and off so we dont freeze the rez.
Just not sure how and which one to wire up to my home made chiller. My thoughts are there is a switch that lets the dehumidifier know when the moisture bucket is full. It basically just cuts the power to the unit. I am thinking if I replace this switch with the water temp thermostat it would work but not sure. switch with rubber band around it is the switch i am speaking of
any help would be appreciated.
I have included pics for reference.

Put it on a timer. Simple. 15 mins every 2 hours would be a good start imo.

hondagrower.
thats what I think i will do. I have everything set up i have the timer and everything.
But now I have been turned off from using it till I do a little more research. I am getting mixed opinions on weather metals will react and harm my plants.
Love to hear your all thoughts

The copper and galvanized steel will certainly react with a nutrient solution compared to titanium or stainless. How much (if any) harm would be evident on the plants I don't know.

Edit: talk of copper poisoning https://www.rollitup.org/t/4-bucket-rdwc-suggestions-encouraged.891418/page-3#post-12118357

Maybe install the exchanger in an insulated cooler filled with water and then pump the cold water into a stainless wort coil sitting in the nute solution.

I can't see the point of a diy chiller. After all is said and done,that is if you value your time and effort,it is damn near as much as buying one. You will definatly poison your plants with copper aluminum tin,more than likely lead from the solder.The only way around is a stainless heat exchanger. Just my opinion though.Good luck with the project.

sanjuan... Yah I have pretty much decided against it after all I have read. Sucks because it was going to be a cheap quick easy fix to the heat issue I have. But its not worth hurting my girls. I am in the process of insulating my rez and grow buckets. My water temps never from what I have seen have gone over 72 but thats cutting it pretty close to the danger level. Right now 2 liter bottles changed every 4 hours while the light are on keeps the temps down and once everything is insulated I think ill be ok.
Igotthe6...
The purpose of a D. I. Y chiller is to save money and to also have fun building things.
As far as my time and money the dehumidifier was free and it took me all of 15 minutes to take the thing apart and move the cooling coil forward into a rez.
So really not much time or effort. Trust me brother if I had the money Ide invest in the chiller. 1. because thats what its made for and 2 I would be certain that the water will be at the temp i need it to be.
Besides I did choose RDWC system over all the methods of growing mostly because it allowed me to mess with things and allow me to put my DIY self to work.
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Thanks everyone for your advise and comments.
Love being here Love growing love learning...
Peace