1. Oil Safety Control

2. Operation Mechanical A. Differential Pressure
1. The oil pressure control must determine the difference between the suction pressure and the oil pump outlet pressure

3. i. Crankcase pressure is different from atmospheric pressure.
ii. Same as suction pressure at service valve
2. Capillary used for testing both crankcase and oil pump outlet
3. Pressure oppose each other one trying to open switch and the other trying to close it

4. 3. Adjustable spring will add pressure
3. Adjustable spring will add pressure so as not to shut during start up (until pressure has been established)
4. Oil pressure must not drop below manufacturers recommended min. Or commonly cut out at 12 psi

5. 2. 120 volt heater wired in series with the diff switch
2. Electrical
A. Time delay circuit
1. The control must have a time delay so that the pump can establish pressure
i. If time delay were not present the unit would never be allowed to come on
volt heater wired in series with the diff switch

6. b. Once open they require manual reset
ii. If the heater is allowed to operate long enough it will open the set of contacts and open the controller
iii. 90 – 120 seconds
3. Control contacts
a. Normally closed
b. Once open they require manual reset