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
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Revision 2.7 Page 58 of 83
Mercury Plant Controller Installation Guide
Operation (Fuzzy)
Once the controller has been set-up and configured, normal operation will resume. If the appropriate Type has
been selected the controller will operate using a “fuzzy logic” based control algorithm. The controller will determine
the stages to bring on and off using the fuzzy logic rules and adhering to the starts/hr criteria. The response time
for devices switching on and off can be varied by adjusting the response on and response off parameters (1 is the
slowest response, 60 is the quickest). The fuzzy logic will attempt to optimise the compressor starts and keep them
at a minimum. Before a compressor or fan is switched on, Relay 1 will energise and the variable output will ramp to
100%, when it reaches this point, the fixed device (compressor, loader or fan); will switch on and the variable
output will begin its cycle again starting from 0%. When demand is satisfied, and all compressor relays are off, the
variable output ramps down 0%, if demand is still satisfied, the enable relay de-energises.
Operation (Staged)
Staged operation requires the output relays to be “mapped” to a particular stage. Each stage (there are 12 stages)
has to have at least 1 relay assigned for the controller to operate correctly. More than one relay can be assigned to
stages in a given section and the same relay can be used in multiple stages. Note a relay cannot be assigned in
both Section 1 and Section 2. As the pressure rises above the target setpoint, plus the target above value, the
controller will enter Stage 1 after the stage on delay has expired. At this point any relay assigned in Stage 1 will
come on and the stage on delay timer will be reset. If the pressure remains above the setpoint, plus the target
above value, and the stage on delay has expired for a second time the controller will enter stage 2. At this point any
relay assigned in Stage 2 will come on. Note if a relay has been assigned in Stage 1 but not used in Stage 2 then it
will go off at this point. The reverse occurs when the pressure falls below the setpoint plus the target below value.
The controller will step down the stages using the stage off delay (P-25) until all stages are off.
When using a variable output as the pressure rises above target setpoint, plus target above, the variable speed
output will ramp up from 0% to 100% without following the stage on delay. If the pressure stays above the target
setpoint and the variable output is at 100% and the stage on delay has timed out then the controller will enter Stage
1. At this point the variable output will reset to 0% and start ramping up again towards 100%. If the pressure stays
above the target setpoint and the variable output is at 100% and the stage on delay has timed out then the
controller will enter Stage 2. As the pressure drops below the setpoint, minus the target below, the variable output
will ramp from 100% down to 0%, once the stage off delay expires the controller will stage down. Note if the
variable output reaches 100% and the stage on delay has not expired the output will remain at 100% until the stage
on delay has expired.
For example if set to dual Pack and pack 1 has 4 Compressors the following could be set: -
Sect1 Stg1 : Rly 1 =On, Sect1 Stg2 : Rly 1 and Rly 2 = On, Sect1 Stg 3 : Rly 1 ,Rly 2 and Rly 3 = On. Sect1 Stg
4 : Rly 1, Rly 2, Rly 3 and Rly 4 = On. This would stage relay 1 through to four on after the appropriate stage delay
if the pressure is above the target setpoint and differentials.
Pack 2 would start as follows:-
Sect2 stg1: Rly 5 = On (Note: Starting at Relay 5 as the first 4 relays have already been allocated to Pack 1)