Carrier 30RBP-170R - Page 65

12.2.4.2 - Total heat recovery operation
Total heat recovery system:
For this option, a dual-circuit plate heat exchanger is installed in
series on air-cooled condensers on the compressor discharge line
on each circuit. The refrigerant ow always passes through the
recovery exchanger, ensuring hot water is produced as soon as
the unit is operating. Refrigerant accumulators enable the
machine's performance to be optimised in all operating modes.
Since there is no isolation valve or solenoid valve on the refrigerant
circuit, hot water production is switched o󰀨 by actuating a three-way
valve and/or a variable ow pump on the hot water hydraulic circuit.
(See the control manual)
Variable water ow control:
Heat recovery mode is activated or deactivated using a digital
input (see the control manual).
A 0-10 V output is available on the unit electronic board to control
either a three-way valve connected to a xed speed pump or just
a variable ow pump. The control regulates the temperature by
adapting the water ow which passes through the heat recovery
condenser and the air speed in the air-cooled condenser.
It is very much not recommended to suddenly stop or increase
the water ow rate at the heat recovery exchanger terminal.
A three-way valve or a variable ow pump must be installed to
ensure a smooth transition between recovery mode and standard
mode.
This control also guarantees a minimum entering water temperature
when the recovery is started up, to protect the compressors from a
low condensing temperature. (See the control manual)
Frost protection:
The low water temperature cutout option (41C) for the condenser
with heat recovery comprises electrical heaters which are activated
if the outdoor air temperature is below 3 °C and if the machine is
not running. The heat recovery circuit pump is then activated.
A ow switch allows start-up problems with the pump to be
detected, and prevents the BPHE freezing.
Note:
- If the heat recovery is not used during the winter, it is
preferable that the water circuit is drained.
- If there is glycol in the hot water loop, it is possible to
congure it and deactivate the frost protection on the
water-cooled condenser side
Operation in cooling mode only (without heat recovery):
During standard operation, the heat recovery condenser is subject
to the outlet gas from the compressors which can reach
temperatures of above 100°C. This phenomenon could eventually
cause damage to the components of the heat recovery hydraulic
circuit. To prevent this, water circulation is activated (actuation of
the pump and/or opening of the three-way valve) to keep this
temperature below 95 °C. Above this temperature, an alarm is
triggered and the machine stops.
To prevent this alarm being triggered, it is recommended that for
prolonged operation in cooling mode only without any heat
recovery (during the summer, for example):
- The heat recovery water loop is drained and the heat recovery
demand deactivated.
- Or, the heat transmitted to the hydraulic circuit is constantly
either being used or rejected.
Note: Due to the risk of burns, the heat recovery condenser
and the hydraulic piping are delivered with insulation.
The installer is responsible for ensuring the safety of anyone
working on these components.
12 - OPTIONS
65