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Mode 3 Relay Contact Conguration
After choosing which relay you want to use as the primary output device the E30’s
menu asks you how you want the chosen relay’s contacts to behave. If you
choose normally open the contacts of the relay will remain open until the system
pressure reaches the set snap pressure, at which point the contacts will change
state and close.
If you choose to have the relay contacts normally closed then on boot up the relay
will close its contacts and they will remain closed until the system pressure
reaches the snap pressure, at which point they will open.
Mode 3 Set Pressure
After choosing the output relay’s contact conguration the E30 menu asks you to
enter a set pressure. The set or snap pressure is the pressure at which the switch
will change state from on to off or from off to on, depending on how you have
congured the relay’s contacts. Enter your required set pressure in the range 7
to 2000 kPa or 1 to 290 psi. Press the (P) button to record your setting and move
to the next screen.
Mode 3 Delta Pressure
Once the set pressure is conrmed the E30 asks you to enter a delta pressure.
This is the differential pressure or difference between the on and off pressure you
require. The range of adjustment is 7 to 140 kPa or 1 to 20 psi in increments of
7 kPa or 1 psi. The higher the value you enter the more stable and tolerant the
switch will become to minor pressure uctuations. As an example of the way the
set and delta pressures work consider a set pressure of 500 kPa and a delta
pressure of 14 kPa.
Assume also the E30 is congured so its output relay contacts are normally
closed. On boot up the E30 will close its relay contacts and it will open them if the
system pressure rises to 514 kPa. The pressure may then rise further, however,
the E30 will not respond unless the 2200 kPa excess pressure alarm is activated.
If the system pressure falls the E30 will ignore the pressure drop until it reaches
500 kPa, at which point the chosen output relay will revert to normally closed.
To summarise, the delta or differential pressure will sit on the high side of the set
pressure. This shifts the high pressure switching point to a point equal to the sum
of the set pressure and the delta pressure, 500 + 14 = 514 kPa. On a falling
pressure the change of state of the chosen relay’s contacts will occur at the set
500 kPa pressure.
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