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Old May 30, 2016   #55
Rosedude
Tomatovillian™
 
Join Date: Apr 2016
Location: California
Posts: 126
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It seems like you are trying to build something that is more complicated than it needs to be. A rubber hose with a liquid in it is not going to be a very efficient way of transfering heat to cold wet soil. It could work, but right away you are starting with an inefficient system, all in the name of saving money.

I looked at your ideas for grow lights that would go in this converted freezer and I could see you were asking for trouble.

Your heater idea lacks the important thermostatically controlled relay that will shut the heater off when the desired temperature is reached. The thermostat is the key to success. There are plenty of heat sources you can connect to this thermostat that will work better than your hose and pump idea--a food warming tray from a garage sale would be great. You can get a thermostat control relay that you can connect to anything from a crock pot to a blow dryer or a coffee cup heater or a ski boot warmer. One that I have used is RANCO ETC-111000 Digital Cold Temperature Control. I got it for about $50 from Amazon but other places have it cheaper. Here is a link to wire it up so it will work with any electric heating device that has a plug
http://www.instructables.com/id/Wiri...-Temperature-/

You can even use this controller with the heater/pump you have started to build. It really doesn't matter how many hoops of tube you have as long as the fluid in the tube is as hot or hotter than the temperature you want for your plants. If your fluid temperature is hotter or you have more surface area for heat transfer it can make the heat transfer work faster, so more hoops could be better, but unless you know the heat conductance of all of the materials in your system plus the prevailing ambient temperature, and the diameter of a hoop you will have a hard time calculating exactly how many hoops you will need.

Last edited by Rosedude; May 30, 2016 at 09:02 PM.
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