240
FORM 160.54-M1
ISSUE DATE: 10/25/2019
SECTION 28 - HEAT RECOVERY
JCI COMPANY CONFIDENTIAL
JOHNSON CONTROLS
The Control Valve Output Settings keys are used to config-
ure the output signal to the Heat recovery Control Valve.
The Type setpoint is used to make the control signal ei-
ther 0 to 10 VDC or 4 to 20mA. The Auto setpoint is used
to place the control in Automatic Mode. The Set setpoint
places the valve control in manual. It is used to manually
position the control valve at any position between 0.0%
and 100%. The Control Valve Control Mode shall be re-
set to Auto upon logging out of Service Level Access. The
Control Valve Control Mode data box displays the Operat-
ing Mode as MANUAL or AUTO as appropriate.
The PID Output setpoint is used to configure the signal
to the Control Valve to be DIRECT or REVERSE act-
ing (default DIRECT). In this application, it should be
set to DIRECT. The output for each setting is per the
following table:
CONTROL
VALVE
OUTPUT
TYPE
PID
OUTPUT
PID
CONTROL
0% OUTPUT
PID
CONTROL
100%
OUTPUT
0-10V
Direct
0V
10V
0-10V
Reverse
10V
0V
4 to 20mA
Direct
4mA (2V)
20mA (10V)
4 to 20mA
Reverse
20mA (10V)
4mA (2V)
If the chiller is equipped with both Heat Recovery and
Head Pressure Control (See
) and both are enabled, there is
not a Control Valve for each feature. Rather, there is one
common valve that is either performing Hot Water Con-
trol for Heat Recovery or it is performing Head Pres-
sure Control. It will not be performing control for both
features at the same time. Normally, it will be perform-
ing Hot Water Control until certain operating conditions
cause it to switch over to Head Pressure Control. The
PID Control Mode displays which feature is control-
ling the valve at any given time. When performing Hot
Water Control, HOT WATER is displayed. When per-
forming Head Pressure Control, HEAD PRESSURE is
displayed. There are also conditions under which it not
controlling either feature, in which case INACTIVE is
displayed and the valve is set to 0% position. Which fea-
ture is controlling the valve at any instant and when it is
inactive is determined by operating conditions as shown
in the following flow chart.
FIGURE 94 -
HEAT RECOVERY FLOW DIAGRAM
LD27942
Heat Recovery /
Head Pressure
Control Valve
Hot Water
Control
Enabled?
YES
YES
Hot Water
Control Active
PID Control Mode
is Hot Water
Flow in Heating
Condenser?
NO
Head
Pressure
Control
Enabled?
YES
YES
Run > 5 Min
No Coastdown
No Soft
Shutdown?
Hot Water
Control
Not Active
Hot Water
Control
Not Active
Head Pressure
Control Active
PID Control Mode
is Head Pressure
Head Pressure
Control Not Active
PID Control Mode
is Inactive
Valve Output = 0%
NO
NO
NO
Chiller
Running?
YES
Hot Water
Control
Not Active
NO