Thermal "Protectors" & Fuses

For those starting out and building their first cookers, I would like to clarify a point on the thermal controls used for ISECs. Multiple-use thermal switches (referred to in industry to be Thermal PROTECTORS), which shut off at a set temperature to regulate how hot the ISECs get, are used in conjunction with one-time use thermal fuses which protect from in-home fires.

The thermal switch used for ISECs are rated at 10A for 24V DC. Because many conventional thermal switches are built for AC circuits, they tend to fail and burn out quickly when used in ISECs. We recommend using thermal "protectors" (search thermal protector instead of thermal switch) which are used to shut off motors if they overheat. See these two sites for examples. We buy these for $5 each in the US, but many other international suppliers sell them for under a dollar, and even less if buying in bulk.

Thermal fuses will be connected in series with the thermal protector, and are meant to blow and destroy themselves if the thermal protector doesn't switch off, stopping any current from continuing into the heater as a last-line defense against fires in case the thermal protector burns out. Their temperature rating should be higher than the thermal switch/protector; we have been using 220C or 216C thermal fuses with thermal protectors at 180C.

Hope this helps!

Jefferson

Hi Jefferson, your post is very helpful ! Thanks !

This is great. The problem is that we can't easily get these thermal protectors, even in the USA. I bought a small number inexpensively on Ebay. For most of these purchases, you need to buy at least 1000, which is going to be over $100. We can afford this if many people are going to use them, but can we share them? Does anyone have a different idea?

Hello Research Team,

As a follow up from yesterday's meeting, I searched for possible vendors for thermal protectors in India via a website known as India Mart (https://www.indiamart.com/) - which aims at products for industries. The best deal I could find and it's details are mentioned below.
Thermal Protectors:
Supplier name: RN Controls ,Coimbatore, State of Tamil Nadu
Min quantity : 100( but they agreed upon 25 as I told them it's an academic research project)
Price :Rs.50 / approx. 0.7 dollar per piece
Max : Temp 175 deg. Celcius. ( according to them it's quite rare requirement, no one really ask for thermal protectors beyond 160 deg. Celcius. Quoting them: "This is NC
It will cut off at 175deg +/-5degs
And reset at 30deg less than trip temp."
Max current limit: 8A.

I have attached the detailed specification. Please let me know if you are unable to view it. I can mail you.

Final question: shall I go for these?

Got it !
Thanks
Bidjanga