User guide

Revision 1.0 Page 17 of 29
Warning
Please Note
The specifications of the product detailed on this
Set-Up Guide may change without notice. RDM
Ltd. shall not be liable for errors or for incidental
or consequential damages, directly and indirectly,
in connection with the furnishing, performance or
misuse of this product or document.
Ensure that all power is
switched off before
installing or maintaining
this product
Mercury 3 M & E Installation Guide
www.resourcedm.com
Load Shedding
Used on CO2 sites for load shedding on CO2 Compressor Faults or CO2 Vessel High Pressure Alarms.
Cases can be put into a “CO2 Case Off” mode which will open the LLV/EEV and stop the fans to reduce the load on the pack or to
reduce the CO2 vessel pressure.
See: RDM CO2 load shedding user guide.
Superheat Options
The superheat for EEV control can be calculated using different means to suit the application;
 Based on the value of the Evaporator and Suction line temperature probe inputs connected directly to the controller.
 The local Suction line temperature probe and a remote suction pressure value broadcast by a Plant/Intuitive Pack controller on
the same IP network. The pressure received from the Plant/Intuitive Pack controller is converted to a temperature based on the
gas type being used by the system. Using an IP Futura or Mercury Switch or built-in IP.
 The local suction line temperature probe and a local suction pressure measured by a transducer connected to the controller’s
internal transducer input.
 The local suction line temperature probe and a local suction pressure measured by a transducer connected to the refrigeration
case island Mercury Hub (PR0018-PHI). The pressure read from the Mercury Hub pressure transducer is converted to a
temperature based on the gas type being used by the system. This temperature is transmitted to all controllers connected to
the Mercury Hub.
EEV Control Using Pressure
There are several ways to use the suction pressure to calculate the evaporator in temperature.
Local Analogue Input – mA or V
(P17 set to Trans mA or Trans V) A suction transducer can be connected directly to the analogue input of the controller. 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 (P-31 to P-36) will need to be set accordingly.
Mercury Switch (PR0018-PHI)
(P-17 set to Rem1) The Mercury Switch can be used for EEV control on an Island by island basis. 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 recommended
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
(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)
(P-30) set to ID of Plant Pack Controller (Rotary Switch Setting), (P-31) set to refrigerant type, (P-32) set to pressure units Absolute or
Gauge
Maximum Operating Pressure (MOP)
MOP is a remote command sent from the Mercury switch (PR0018-PHI) to the controller to either close or reduce the EEV valve opening
when a predetermined pressure is reached. This MOP value is configured in the Mercury switch setup. When the Mercury Switch
generates the MOP alarm the controller reduces the maximum valve opening to this percentage. For example if the “Div Value”
parameter is set to 50% and the MOP alarm is generated then the maximum valve opening will be limited to 50%. For M controllers the
LLV is closed for the MOP alarm duration.
Note – for the MOP command to work, the device must have serial comms and be connected into the RS232 ports of the PHI hub.