Thermostat Switch question

Thread Starter

gil80

Joined Aug 20, 2019
11
Hi all. New here.
I'm trying to fix a water heating element for a water distiller.

This device uses a 750W heating element and a thermal circuit break will disconnect it from power once the water has depleted.

I don't know exactly what is the temperature rating of the thermostat switch. For what it's worth, I'm using a brand called Genie Water Distiller (counter top). I'm assuming once the water is gone from the kettle, the metal surface at the bottom gets hot and the thermostat opens the loop.

The problem I'm trying to solve is that the thermostat disconnects the power too early. If the whole distiller can hold 4 litres of water, the thermostat will engage when there are still 2 litres or sometimes 1 litre of water in the distiller. Clearly indicating the thermostat is faulty.

I opened the water distiller and saw that the ON switch is the thermostat itself.

For the thermostat switch, I was looking at: https://www.jaycar.com.au/normally-open-thermostat-switch-100-degrees/p/ST3836 as it's the same shape, but not sure about specifications.

Questions:
1. Do I need the normally open switch? the description is confusing:
"They operate once the temperature reaches a specified limit and automatically reset to their original normally open state once the temperature drops below its rated temperature."
That underline statement confuses me.
Does it mean that it will disconnect (set to normally open) the power once it reaches a 100 degrees, i.e., set to OFF, and once the temp goes below 100 it can be set to close (connect the power again) by pressing it manually?

2. Do 100 degrees seem reasonable?

3. Do you require photos of the circuitry?

Thank you.
 

ericgibbs

Joined Jan 29, 2010
10,444
"They operate once the temperature reaches a specified limit and automatically reset to their original normally open state once the temperature drops below its rated temperature."
hi gil,
That thermo switch is open below 100C and closed above, its not not suitable for over heat cut off.
E
 

AlbertHall

Joined Jun 4, 2014
10,226
Can you see any markings on the original thermostat?
I would expect the temperature to be higher than 100C as the water will be at that temperature once it boils.
Also as per @ericgibbs it needs to be normally closed (NC).
 

ericgibbs

Joined Jan 29, 2010
10,444
This phenolic-housed unit attaches to any metal surface which needs to be heat monitored. When the surace meets or exceeds a certain temperature the SPST bi-metalic element goes open circuit.
Hi,
Looks OK, check what are the contact ratings ,Volts and Current, contact them online.
E
 

Thread Starter

gil80

Joined Aug 20, 2019
11
Can you see any markings on the original thermostat?
I would expect the temperature to be higher than 100C as the water will be at that temperature once it boils.
Also as per @ericgibbs it needs to be normally closed (NC).
Here are some photos of the thermostat switch
IMG_20190821_215442.jpg
IMG_20190821_215509.jpg

Here is the circuit showing the switch and the button
IMG_20190821_211745.jpg
 

Thread Starter

gil80

Joined Aug 20, 2019
11
So looking at eBay Australia, I found this:
https://www.ebay.com.au/itm/40-160-C-Thermostat-Temperature-Thermal-Switch-Normally-Open-Closed-NO-NC-KSD30/252977291697?hash=item3ae69f21b1:m:mTEsBn21CpkOaNAKyRqBh3w&var=552013034276

I think of selecting the 110c and as mentioned, the normally closed.

Why 110c and not 115c? That is because based on my observations, the thermal switch should engage earlier when the water runs out, in order to avoid cooking the residual chemicals that are left over as sediments at the bottom of the kettle.
 

ericgibbs

Joined Jan 29, 2010
10,444
hi gil,
I would use that thermo switch,it looks a close match for the original.
The original has the numbers 115 on the body which I would read as 115C, so a 110C cut out should do what you need.

E

Let us know how it goes.
 
Last edited:

Thread Starter

gil80

Joined Aug 20, 2019
11
Can anyone help?

I can't seem to find a thermal switch of 110c with manual reset.
The website of the original manufacturer does not have an email address to contact.

The ones that I do find, have the contact fins at 90c angle, instead of the one I originally had (photo above).
I looked in ebay and aliexpress but I can't find it at all.
 

Danko

Joined Nov 22, 2017
963
The problem I'm trying to solve is that the thermostat disconnects the power too early. If the whole distiller can hold 4 litres of water, the thermostat will engage when there are still 2 litres or sometimes 1 litre of water in the distiller. Clearly indicating the thermostat is faulty.
1. At first you should repair water level sensor.
2. Thermal circuit breaker used for emergency case only.
3. Heater has big thermal inertia and high temperature (about 1000°C) of heating element inside.
Therefore, even thermal circuit breaker will OFF at 105°C, temperature of heater surface will rise up to 200...250°C by inertia.
 

Thread Starter

gil80

Joined Aug 20, 2019
11
1. At first you should repair water level sensor.
2. Thermal circuit breaker used for emergency case only.
3. Heater has big thermal inertia and high temperature (about 1000°C) of heating element inside.
Therefore, even thermal circuit breaker will OFF at 105°C, temperature of heater surface will rise up to 200...250°C by inertia.
This unit doesn't have water level sensor.
The faulty part is the thermostat.

What I need is a manual reset thermostat.
 

shortbus

Joined Sep 30, 2009
7,838
What I need is a manual reset thermostat
Why? The switch/thermostat should reset it's self on cool down. A manual rest before cool down would just have the switch turn off again because it is already at temperature.
"A thermal switch (sometimes thermal reset or thermal cutout (TCO)) is a device which normally opens at a high temperature (often with a faint "plink" sound) and re-closes when the temperature drops" From; https://en.wikipedia.org/wiki/Thermal_cutoff
 

Thread Starter

gil80

Joined Aug 20, 2019
11
Why? The switch/thermostat should reset it's self on cool down. A manual rest before cool down would just have the switch turn off again because it is already at temperature.
"A thermal switch (sometimes thermal reset or thermal cutout (TCO)) is a device which normally opens at a high temperature (often with a faint "plink" sound) and re-closes when the temperature drops" From; https://en.wikipedia.org/wiki/Thermal_cutoff
The manual reset switch is the ON button for the distiller.

When the water reaches 110 degrees, the thermal switch will auto open and shut down the system.
Only after it’s cooled down below a certain degree, one can push it again to close contact.
This is a normally closed manual reset thermal switch.
 
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