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FORM 160.54-M1
ISSUE DATE: 10/25/2019
(SOFTWARE VERSION C.OPT.01.21.307 AND LATER)
This option uses two tube bundles in the condenser.
The lower bundle is the standard condenser bundle and
is piped to the cooling tower water source. The upper
tube bundle is used to recover waste heat rejection for
use in a closed loop heating circuit. Chillers equipped
with this feature are also equipped with the Hot gas
bypass feature.
On a heat recovery chiller, the chiller primary control
remains the cooling load. So, the compressor capac-
ity is still functioning according to the Leaving Chilled
Water Temperature setpoint.
The desired hot water temperature leaving the heating
bundles is obtained by regulating the heat rejection
through the standard lower tube bundle (sourced by
cooling tower or other water circuit). This is done by
controlling the temperature of the Return Condenser
Water Temperature (by tower bypass circuit to elevate
the temperature of the return condenser water) or vary-
ing the condenser water flow. This control can be per-
formed by the OptiView Control Center or an external
controller. If the OptiView Control Center is used to
perform this control, The Heat Recovery Control Valve
is modulated to control the Leaving Heating Condens-
er Water Temperature to the Hot Water setpoint. The
control output to the valve is Direct Acting (when the
Leaving Heating Condenser Water Temperature rises
above the Hot Water setpoint, the valve is driven more
open to provide greater cooling to the standard lower
tube bundle).
The heat recovery bundle is provided with a Leaving
Heating Condenser Water Thermistor, Return Heating
Condenser Water Thermistor and a Heating Condenser
Water Flow Switch. The heat recovery circuit control is
only active when the flow sensor indicates flow.
If the chiller is equipped for Heat Recovery, the feature
must be ENABLED on the SETUP Screen. Otherwise,
it must be DISABLED. Once enabled, the HEAT RE-
COVERY Screen is available from the CONDENS-
ER Screen. All of the Heat Recovery parameters are
displayed on this screen. If Head Pressure Control is
also enabled, the Head Pressure parameters appear on
the HEAT RECOVERY Screen (there is no separate
HEAD PRESSURE CONTROL screen in this configu-
ration).
JOHNSON CONTROLS
SECTION 28 - HEAT RECOVERY
JCI COMPANY CONFIDENTIAL
The heat recovery feature cannot be used
with the Heat Pump feature. If HEAT
PUMP Duty is enabled, heat recovery will
be disabled and locked.
INPUTS/OUTPUTS
The I/O used for the heat recovery feature is:
• Leaving Heating Condenser Water Temperature
Thermistor input
• Return Heating Condenser Water Temperature
Thermistor input
• Heating Condenser Water Flow Switch input
(paddle or thermal type)
• Heat Recovery Control Valve output (0 to 10 VDC
or 4 to 20mA)
The above are interfaced to the LTC I/O Board 031-
02895-000 as shown in Figure 92 on page 238 (the
thermal flow switch connects directly to the mi-
croboard). The operation of this I/O Board is explained
in SECTION 27 - LARGE TONNAGE CHILLER (LTC)
I/O BOARD 031-02895-000/001. The microboard
communicates with this board using RS-485 Mod-
bus serial communications. The microboard reads the
Heating Condenser Water Temperature Thermistors
and the Flow Switch status via this interface. It also
drives the Heat Recovery Control Valve via a 0 to 10
VDC or 4 to 20mA output as described below.
Use Figure 17 on page 66 to convert the heating
condenser thermistors voltage output to a (°F) tem-
perature value.
CONTROL
If the OptiView Control Center is used to control the
heat recovery valve, then the hot water control setpoint
on the HEAT RECOVERY screen must be enabled. If
disabled, only the heat recovery inputs are displayed.
When enabled, all of the control parameters are dis-
played on this screen as described below.
28
237
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