Installation guide

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
Revision 2.7 Page 50 of 83
Mercury Plant Controller Installation Guide
To reset the run proof for any stage, after maintenance, and return a compressor back into the control strategy use
the menu item Override. The override option is used to manually turn on the compressor output. If the proof signal
is returned within the allotted time delay the compressor is allocated back into the control strategy; if the proof isn’t
returned the compressor relay will go off and remain out of the control strategy.
Alternatively the alarm can be cleared remotely by changing parameter P472 from 1 to 0 (On to Off). This clears all
run proof alarms on all compressors which are currently out of the control logic due to run proof feature. Now
change P472 from 0 to 1 (Off to On). The compressor(s) will then be available for selection by the control logic. If
the compressor is selected by the control strategy and the run proof signal is then not returned within the allotted
time delay then it will fail and will be removed from the control logic again.
Gas Dump
Gas Dump Enable (P-490/491). In Fuzzy pack control the Gas dump relay will come on when the Suction Pressure
drops below the Set Point (P-20/40) plus the Gas Diff (P-492/493) and all but the last compressor has turned off.
When an Inverter output is configured using Fuzzy pack control the Gas dump relay will come on only when the
Inverter is active, i.e. above 0% and all other Compressors configured in that section are off.
With Staged pack control the Gas Dump relay will come on only when last compressor is running.
The Gas dump relay will go off again when: -
The pressure rises above the Set Point (P-20/40)
Or
When the last stage compressor goes off, or Inverter Enable is turned off.
Compressor Loaders
Parameters P495/496 determines the order in which the compressor loaders are switched off.
This gives the option to turn off one compressor and its loaders before turning off the next compressor, or to switch
off all the loaders first leaving compressors running unloaded.
If P495/496 is set to 0 (Off) then a compressor’s loaders and body will be switched off before any other compressor
loader is switched off.
If P495/496 set to 1 (On) then all loaders on all compressors will be switched off before any compressor body is
switched off.
Example 1 (Type 1 Fuzzy)
Pack set up: 2 compressors with 2 Loaders each
Sect 1 stage 1 = Comp. Sect 1 stage 2 = Loader. Sect 1 stage 3 = Loader.
Sect 1 stage 4 = Comp. Sect 1 stage 5 = Loader. Sect 1 stage 6 = Loader.
Parameter P495 = 0 (Off)
Switching On sequence: Pressure above set point + diff
First compressor comes on. Compressor loader 1 comes on. Compressor loader 2 comes on.
Second compressor comes on. Compressor loader 1 comes on. Compressor loader 2 comes on.
Switching Off sequence: Pressure below set point – diff
One compressor loader 2 goes off. Compressor loader 1 goes off. Compressor body goes off.
Next compressor loader 2 goes off. Compressor loader 1 goes off. Compressor body goes off.
This configuration switches off one compressor and its loaders before switching off the next compressor loader.
Thus leaving one compressor fully loaded until the first one is completely off.