Switch set points

[Lc85]

We have a lube oil unit. we have two separate temperature switches. One of the switches will inhibit the machine start if the temperature is less than 10'C. The other will switch on the oil heaters when the temperature is less than 10 and switch the heaters off when the temperature is equal to 20'C. My question is does this second switch require 2 set points?


Thanks

 

[Skogsgurra]

Either two setpoints or one setpoint and 10 C hysterisis.

Gunnar Englund

http://www.gke.org

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[DRWeig]

Attached is one that I like, adjustable hysteresis 1°C to 30°C (aka deadband, differential, etc...):



Best to you,

Goober Dave

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[LionelHutz]

Yes, without a deadband the heaters will be cycling on and off wearing out the switch contacts.

You also need the heaters to be on until the oil temp gets far enough above 10*C that the inhibit switch will reliably work.

The inhibit operation switch will need a dead band of some sort as well.