Emerson E2 8RO, 8IO, and MultiFlex Outputs, Wiring Form C Contacts, MultiFlex Relay Outputs

NAME}:{UNIT NUMBER}:{BOARD NUM- BER}:{POINT NUMBER}.”

Select Eng. Units The Select Eng. Units field is where you may select how the ON and OFF states of this point are displayed and represented in E2’s setup fields and status screens. By default, digital inputs have ON-OFF engineering units, meaning when the input is ON or OFF, the input will be represented as “ON” or “OFF” in the system software.

Since the controller looks at only the actual state of the point when it uses the input for control purposes, it is not necessary to define engineering units for dig- ital inputs. However, selecting units that are appro- priate to the input’s function (such as BYP or NO_BYP for inputs that initiate bypasses) will make the input’s state easier to read and understand.

To choose an engineering unit, press  (LOOK UP) to select.

Push Button Mode? Digital inputs may be set up as “push button” inputs by changing this field to “YES”. Push Button Mode is used to detect when a push button (Momentary) switch has been pressed. When a button press is detected, the input will turn ON for one second, and then turn OFF. If the push button is pressed multiple times, the input will turn ON and back OFF for the same number of times that the button was pressed. The pushbutton input is designed to be connected to any application that has a BYPASS input. It may also be connected to the input of the Pulse Accumulator application to track the number of times the button has been pressed.

If the pushbutton input is connected to an applica- tion’s BYPASS input, a single button push will cause the application to go into bypass. If the push button is pressed three times within ten seconds, the applica- tion will then cancel the bypass. An application must be in bypass mode for at least one minute before it may be cancelled.

Output This field displays the link between the input and its application(s). You do not need to enter any- thing in this field. You will be able to link applica- tions to this point during the application setup process.

9.2The 8RO, 8IO, and MultiFlex Outputs

The 8RO, 8IO, and MultiFlex combination I/O boards have relay outputs that close when called to be ON and open when called to be OFF. When an output point is closed (ON), the LED directly above the output terminal glows red. These boards use Form C contacts that deter- mine if the connection will be open or closed during power failure. A fail-safe dip switch is used to determine connection status during network failure.

9.2.1Wiring Form C Contacts

Figure 9-8shows how to wire the three-terminal Form C contact.

One wire of the two-wire connection should always be connected to the middle terminal. The second wire must be connected to the N.C. terminal (if you want the relay to be closed (ON) during power failure) or the N.O. terminal (if you want the relay to be (OFF) during power failure).

RELAY IS	RELAY IS
CLOSED	OPEN ON
ON POWER	POWER
FAILURE N.C.	N.O. FAILURE N.C.	N.O.

Figure 9-8- Form C Contact Wiring

9.2.2MultiFlex Relay Outputs

The MultiFlex boards that have relay outputs (all mod- els except the MultiFlex 16) each have eight relays that energize and de-energize to control output loads.

When setting up an output on one of these relays, you must make two important decisions:

1.Do you want an ON command from your control- ler to mean “energize the relay” or “de-energize the relay,” and

2.When the relay is de-energized, as is the case when the 8RO or 8IO goes off-line or loses power, do you want the contacts to be OPEN or

CLOSED?

Decision #1 is made by setting the fail-safe switch. This is a bank of eight switches labeled S2 on the 8RO, and 8RO-FC, S3 on the 8IO, and S1 on the MultiFlex plug-in output board. Each switch corresponds to an out- put on the board (switch #1 = output #1, etc.).

Decision #2 is made either by setting a fail-safe jumper (for old-style 8ROs) or by wiring the load to either the N.O. or N.C. terminals on the Form C contact

9-10 • E2 RX/BX/CX I&O Manual 026-1614 Rev 4 5-JAN-2013