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 59 of 83
Mercury Plant Controller Installation Guide
Other operational features
Floating Head Pressure
When the condenser controller is used in the “Floating Head pressure” mode, the temperature to pressure
parameters must be used to profile a pressure curve from the air on temperature probe for the condenser (P414 to
P419 and P461 to P466). The value read from the temperature probe is added to a “Condenser Offset” (P422) and
then converted to a pressure. This converted pressure replaces the “Target Setpoint” (P01) as the target pressure
and P01 is only used as a default; for instance when the probe is disconnected or develops a fault. Low and high
pressure levels allow for a lower and upper limit to be set for the pressure range.
The air on temperature can be read from probe inputs 1 to 8 and is settable via parameter P-410/P-460. The float
temperature can also be received as a TDB command sent from a Data Manager TDB program. This would allow
for a single probe temperate to be shared with multiple Plant controllers. Please see the relevant Data Builder user
guide with regards to creating a TDB program. The following commands would be used in TDB to send the
temperature data to the Plant controller. If P-410 is set to Remote then “S1 Rem Float” would be used in TDB to
send the remote temperature used for Section 1 condenser float or if P-460 is set to Remote then“S2 Rem Float”
would be used in TDB to send the remote temperature used for Section 2 condenser float.
Drop Leg
When the condenser is used in the “Drop Leg” mode, the temperature measured from the condenser Drop Leg is
converted to a pressure. This converted pressure replaces the condenser pressure transducer and is used in the
control strategy. If the drop leg temperature is lost then the control strategy will revert to using the relevant pressure
transducer.
Drop Leg temperature can be read from probe inputs 1 to 8 or set to remote then read from another pack which is
reading the Drop Leg Temperature and sending temperature via a TDB Program to Input “S1 Rem Drop Leg” or
“S2 Rem Drop Leg”. This is then converted to a pressure and used as Control Pressure
Drop Leg temperature can be read from probe inputs 1 to 8 and is settable via parameter P-41/P-412. The drop leg
temperature can also be received as a TDB command sent from a Data Manager TDB program. Please see the
relevant Data Builder user guide with regards to creating a TDB program. The following commands would be used
in TDB to send the temperature data to the Plant controller. “S1 Rem Float” would be used in TDB to send the
remote temperature used for Section 1 condenser drop leg or “S2 Rem Float” would be used in TDB to send the
remote temperature used for Section 2 condenser drop leg.
Night Set-back
This controller; when in condenser mode has a “Night Set-back” feature for the condenser controller. The variable
output can be set to reduce to a pre-determined level; either by an internal timer, or by times sent to the controller
over the network. (Use a GP Timer channel in a data Manager or Data Director)
There is a High pressure limit, over which the night set-back feature will be turned off. As the pressure reduces
under this limit the night set-back feature is switched on again.
Day Set-back
Similarly, this controller; when in condenser mode has a day Set-Back feature. The Day Set-Back feature uses the
local night Set-Back clock, (if it’s out of the night set-back time, day set-back will be on) Note: - When Set-Back
mode is on, no further fan stages will come on unless the variable output reaches 100%, either by reaching the
high pressure point or Set-Back going off. When configured as a condenser controller, loss of the pressure input
will result in the variable output going to the value defined in P17.