EWWQ090G ÷ EWWQ720L - R410a - Water-cooled scroll chillers
EWLQ090G ÷ EWLQ720L - R410a - Condenser less
EWHQ100G ÷ EWHQ400G - R410a - Heat pump scroll chillers
Water cooled scroll chillers & heat pump
Operation
Manual
Operation Manual
36
EWWQ - EWLQ - EWHQ
Water colled scroll chiller &heat pump
D-EOMWC01203-15EN
5.1.5 Alarm Settings
Factory defaults are set for standard cooling mode, therefore they may not be properly tuned when
working at different conditions. Depending on the application, the following alarm limits need to be
adjusted:
Low Press Hold
Low Press Unload
Evap Water Frz
Cond Water Frz
Low Press Hold
Set the minimum refrigerant pressure of the unit. It is generally recommended to set to a value whose saturated
temperature is 8 to 10°C below the minimum active setpoint. This will allow a safe operation and a proper control
of compressor suction superheat.
Low Press Unload
Set lower than the hold threshold enough to allow a suction pressure recovery from fast transients without
unloading the compressor. A 20 kPa differential is generally appropriate for most applications.
Evap Water Frz
Stops the unit in case the evaporator leaving temperature falls below a given threshold. To allow a safe operation
of the chiller, this setting must be adequate to the minimum temperature allowed by the mixture water/glycol
present in the evaporator water circuit.
Cond Water Frz
Stops the unit in case the condenser leaving temperature falls below a given threshold. To allow a safe operation
of the chiller, this setting must be adequate to the minimum temperature allowed by the mixture water/glycol
present in the condenser water circuit.
5.1.6 Pumps
The UC can manages one or two water pumps either for the evaporator either for the condenser.
Number of pumps and their priority can be set from the menu 4.2.4.
Evap Pump Ctrl
Set number of active pumps and priority
Cond Pump Ctrl
Set number of active pumps and priority
Recirc Tm
This parameter indicates the minimum time for which the evaporator/condenser flow switches must be active
before to start the thermostat control
The following options are available for the pumps:
#1 Only
Set to this in case of single pump or twin pump with only #1 operational (f.e. in case of maintenance on #2)
#2 Only
Set to this in case of twin pump with only #2 operational (f.e. in case of maintenance on #1)
Auto
Set for automatic pump start management. At each chiller start, the pump with the least number of hours will be activated.
#1 Primary
Set to this in case of twin pump with #1 running and #2 as a backup
#2 Primary
Set to this in case of twin pump with #2 running and #1 as a backup
The unit controller manages the pumps differently depending on the water circuit that they belong.
The pumps connected to the load water circuit (water circuit connected with the plant) are started
when the unit switch is set to On. The pumps connected to the source water circuit (water circuit
connected with the cooling tower, water well, etc.) are started only when at least one of the
compressor goes in run. When the unit is configured as Heat Pump with water inversion the
controller inverts the functioning of the pumps. This means that the pump managed for the load
water circuit in cooling mode is managed, instead, for the source water circuit in heating mode and
viceversa.
If the condensing control is set as Pressure mode (see section 5.4) the pumps connected to the
source water circuit are managed in a different way. Each pump is related to one of the two
refrigerant circuits and it is started automatically only when required to guarantee the condensing
target.