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Mercury 2 & Intuitive Mercury EPR Stepper Installation Guide
Superheat Monitoring Using Pressure
There are several ways to use the suction pressure to calculate the evaporator in temperature, this is used for information only and has no control
or alarm functionality.
Local Daughter Card
(P17 set to IoBrd) A suction transducer can be connected directly to the input of the daughter card, the controller will calculate the evaporator
temperature from the suction pressure, and along with the suction temperature probe local to the controller, the superheat is calculated. Please
note that RDM recommend that the evaporator in temperature probe is fitted as the controller will use this to calculate the superheat in the event
of a transducer fault
(Parameters P58/59/75/76/84/91/99) will need to be set accordingly
Mercury Switch (PR0018-PHI)
(P-17 set to Rem1) The Mercury Switch can be used for superheat monitoring on an island by island basis. The evaporator in temperature probe
reading for a case controller can be obtained from the Mercury switch on which the controller is connected. A suction pressure transducer is
connected from the case Island to the 4-20mA input of the Mercury Switch and the pressure read from this transducer is converted to a
temperature based on the gas type being used by the system. This temperature is transmitted to each controller connected to the switch and,
along with the suction temperature probe local to the controller, the superheat is calculated. Please note that RDM recommend that the evaporator
in temperature probe is fitted as the controller will use this to calculate the superheat in the event of a communication loss with the Mercury
Switch. (P-17) allows for the use of this remote temperature provided by the Mercury Switch. Please see the Mercury Switch user document
(PR0018-PHI) for further details.
Remote pressure Direct from a Plant Pack Controller
Using IP Module
(P-17 set to Rem1, Rem2 or Rem3 depending on which input the suction transducer is connected to on the plant controller, transducer input 1, 2
or 3). Set the broadcast ID (P-58) to the ID of Plant Pack Controller (Rotary Switch Setting), (P-59) set to refrigerant type, (P-75) set to pressure
units absolute or gauge
Relay State and functional operation
Relay 1-3 State
Relay 1 off
Relay 1 on
Relay 2 off
Relay 2 on
Relay 2 off
Relay 2 on
Relay and screen states during defrost
State:
Screen:
Def LED:
Stepper Valve (set to closed in DF)
Stepper Valve (set to open in DF)
RLY 3 (set to suction line)
RLY 3 (set to defrost Valve (LLV))
RLY 4 Defrost Relay
RLY 2 Lights relay
RLY 1 Fans (set to on in DF)
RLY 1 Fans (set to off in DF)
Defrost Termination
Defrost termination will occur when the temperature parameter "def terminate" has been reached on the "defrost termination" probe. If the
"defrost termination" probe is not fitted, defrost termination will occur when: -
The "coil in" probe reaches the set point (If fans are selected as "off during defrost")
The "air off" probe reaches the set point (If fans are selected as "on during defrost")
Or
If the "coil in" probe is not fitted, the "air off" probe will be used. If the "air off" probe is faulty termination will occur when the time-out
period has elapsed.
Warning
Ensure that all power is
switched off before
installing or maintaining
this product
Please Note
Function State
Wired
contact
Fans On
N/C
Fans Off
N/C
Lights On
N/C
Lights Off
N/C
Alarm Relay = Alarm
N/C
Alarm Relay = OK
N/C
Pump Down
DEF
On
Closed
Open
Off
Off
Off
On
On
On
Relay 3-4 &
Stepper State
Relay 3 off
Relay 3 on
Relay 4 off
Relay 4 on
Stepper Valve
Off
Stepper Valve
On
Defrost Min
Defrost Max
DEF
DEF
On
On
Closed
Closed
Open
Open
On
On
Off
Off
On
On
On
On
On
On
Off
Off
Revision 1.2a
Function State
Suction or Df Valve Off
Suction or Df Valve On
Defrost Control Off
Defrost Control On
Stepper Valve Closing
Stepper Valve Operating
Drain Down
Fan Delay
DEF
DEF
Off
Off
Closed
Open
Open
Open
On
Off
Off
On
Off
Off
On
On
On
Off
Off
Off
Page 16 of 25
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Wired
contact
N/O
N/O
N/O
N/O
As per I/O
Diagram
As per I/O
Diagram
Recovery
REC
Off
Open
Open
Off
On
Off
On
On
On
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