7 - STANDARD CONTROL OPERATIONS AND OPTIONS
7.7 Additional space heating control
The control provides additional heating control by means of the
optional boiler or standard electric heating management.
7.7.1 Boiler control (optional)
The boiler can be activated as a heating replacement of a
heat pump when the operating conditions are not suitable for
mechanical heating. The unit and the boiler cannot operate
together at the same time.
The boiler is running under the following conditions:
• The unit is in heating mode, but a fault prevents the use of
the heat pump capacity.
• The unit is in heating mode, but works at a very low outdoor
temperature, making the heat pump capacity insufficient. It is
possible to adjust the boiler start-up based on the outside
temperature. By default, the boiler is started when the outside
air temperature is -10°C. This threshold can be modified by
logged-in users in the Heat/Cool Config menu (HCCONFIG).
To set boiler OAT threshold
1. Navigate to the Configuration menu.
2. Select
Heat/Cool Config
(HCCONFIG).
3. Set
Boiler OAT Threshold
[boil_th].
Boiler OAT Threshold [boil_th]
-30 to 15°C
-10°C
7.7.2 Electric heating control
Up to 4 stages of electric heating can be activated as supplemental
or replacement heating when the operating conditions are not
suitable for the mechanical heating.
Electric heating is used to supplement mechanical heating
under the following conditions:
• The unit uses 100% of its available heating capacity:
•
The outside temperature is below a configurable
threshold: “Elec Stage OAT Threshold” [ehs_th].
• The electrical pulldown time elapsed:
“Electrical Pulldown Time” [ehs_pull].
• The unit cannot fully satisfy current heating demand due to
the protection mode, e.g. low entering water temperature.
To set Electric heating stage OAT threshold
1. Navigate to the Configuration menu.
2. Select
Heat/Cool Configuration
(HCCONFIG).
3. Set
Elec Stage OAT Threshold
[ehs_th].
Elec Stage OAT Threshold [ehs_th]
-5 to 21°C
5°C
To set Electric Pulldown Time
1. Navigate to the Configuration menu.
2. Select
Heat/Cool Configuration
(HCCONFIG).
3. Set
Electrical Pulldown Time
[ehs_pull].
Electrical Pulldown Time [ehs_pull]
0 to 60 min
Depending on user configuration, the last electric heating stage
can be used for back-up when the unit is shut down because of
the unit failure or operating envelope protection. Otherwise, this
electric heating stage will not be used even if the heating demand
cannot be satisfied. This electric heating backup option can be
enabled by setting “1 Elec Stage For Backup” [ehs_back] to “yes”
in the Heat/Cool Configuration menu (HCCONFIG).
7.8 Defrost control
When the outside air temperature is low and the ambient
humidity is high, the probability of frost forming on the surface
of the outdoor coil increases. The frost covering the outdoor
coil may decrease the air flow across the coil and lead to lower
performance of the unit. To remove the frost from the coil,
the control initiates the defrost cycle when necessary.
7.8.1 Standard defrost
During the defrost cycle, the circuit is forced into the cooling
mode. The heat (energy) is extracted from the water circuit by
using compressors and reversing the 4-way valve. To prevent the
water loop from cooling down, optional electric heating may be
started. The defrost cycle lasts until the end of defrost temperature
is achieved.
7.8.2 Free defrost
Free defrost is used in order to eliminate a relatively small
amount of frost that has formed on the surface of the coil.
Contrary to the standard defrost session; in the case of the free
defrost session the heat (energy) is absorbed from the air. When
running the free defrost, fans are activated and compressors are
turned off. The free defrost is most efficient when the outside air
temperature is above 1°C.
IMPORTANT: In the case of a large amount of frost
covering the coil, the standard defrost cycle will be started.
7.9 Master/Slave control
The control system allows for master/slave control of two units
linked by the network. The master unit can be controlled locally,
remotely or by network commands, while the slave unit remains
in Network mode.
All control commands to the master/slave assembly (start/stop,
setpoint selection, heating control, load shedding, etc.) are handled
by the unit which is configured as the master. The commands are
transmitted automatically to the slave unit.
If the master chiller is turned off, while the master/slave function
is active, then the slave chiller will be stopped. Under certain
circumstances, the slave unit may be started first to ensure that
the run times of the two units are equalised.
In the event of a communication failure between the two units,
each unit will return to an autonomous operating mode until the
fault is cleared. If the master unit is stopped due to an alarm,
the slave unit is authorised to start.
IMPORTANT: Master/slave assembly can be configured
only by service technicians.
AQUACIAT
CALEO
EN - 24
