Originally Posted by jonurban
this might do what you need:
This switch will open or close the electric circuit when liquid level reaches a specific position. It can be used to activate a pump when liquid level is low, or to open the heating circuit to prevent the damage of the heater. For activating the pump when liquid level is low, the sensor tip should be mounted downwards as shown in the picture below. For cutting off the heating circuit when liquid level is low, the sensor tip should be mounted upwards. Since the switch is rated for 0.8 Amp, a typical wiring is to put it in series with relay (or solid state relay) control loop.
Float Switch(stainless steel Float Switch,Liquid Switch)
Rated voltage: 220VAC/24VDC
Rated curent: 0.8A
Insulation Impedance: >10MΩ
Applied pressure :20/50 Pa
Working temperature: -10 ºC~130 ºC (14 ºF~266 ºF)
Cable length: 17 inchhttp://www.auberins.com/index.php?main_page=product_info&cPath=7_32&produc ts_id=324
I have installed one of those in both my HLT and my BK. It's already saved my HLT heating element once when I got distracted and forgot to turn off the heating element switch while the water drained. See? I told
you that I was easily distracted! For only 11 bucks, it's a very cheap insurance policy.
The float can be turned upside down if you'd prefer to have the switch facing downwards instead of up, btw. It's a very nice SS float switch. Highly recommend them from Auber Instruments.
I made a quick disconnect for them using a standard mono audio jack, so I don't have a long cord dangling when I move the pots for cleaning purposes.