EWWQ090G ÷ EWWQ720L - R410A - Water-cooled scroll chillers
EWLQ090G ÷ EWLQ720L - R410A - Condenser less
EWHQ100G ÷ EWHQ400G - R410A - Heat pump scroll chillers
EWAQ-
- R410A - Air-cooled scroll chillers
EWAQ-
- R410A - Air-cooled scroll chillers
EWYQ-
- R410A - Air-cooled scroll heat pumps
Air and Water cooled scroll chillers & heat pump
Operation
Manual
EWWQ - EWLQ - EWHQ
EWAQ - EWYQ
Air or Water cooled scroll chiller &
heat pump
D-EOMHW00107-15EN
Operation Manual
53
If the evaporating pressure drops below the Low Pressure Unld limit and at least two compressor
in the same circuit are on, one compressor is shut down in order to recover the normal operating
conditions.
This condition is indicated on the controlle
r display in the circuit status as “
Run: Evap
Press Low”. The status is automatically cleared when the evaporating pressure rise above the Low
Pressure Hold limit.
If the evaporating pressure drops below the Low Press Alm limit the related circuit is immediately
stopped and a Low Pressure Alarm is generated.
See section 6.1.7.2 to troubleshoot this problem.
5.3.2 High Condensing Pressure
When the circuit is running and the condensing pressure rises above the safety limits the circuit
control logic reacts at two different levels in order to recover the normal running conditions.
If the condensing pressure rises above the High Pressure Unload limit and at least two compressor
in the same circuit are on, one
compressor is shut down in order to recover the normal operating
conditions.
This condition is indicated on the controller display in the circuit status as “
Run: Cond
Press High”. The status is automatically cleared when the condensing pressure falls below the
High Pressure Hold limit by 862 kPa.
If the condensing pressure rises above the Hi Press Stop limit the related circuit is immediately
stopped and an High Pressure Alarm is generated.
See section 6.1.7.3 to troubleshoot this problem.
5.4 Mode Change-Over (H/P only)
Mode change-over switch is only present on units with the heat pump option. It allows to switch
from heat mode to cool mode and vice-versa. Change over should be performed seasonally,
following the prescriptions required for this specific activity.
When a mode change over will be commanded, the unit will be switched off in order to execute the
exchange of the 4 way valve if installed.
5.5 Backup Heaters (A/C only)
In predefined circumstances and if enabled, the UC may decide to enable the additional backup
heater contact.
With the Q8 switch in the Cooling position the unit will operate in Cool
mode. Cool setpoints will be used. In case of 4 way valve, the
corresponding solenoid valve will be de-energized.
With the Q8 switch in the Remote position the unit will be commanded by
a remote switch. If the switch will remain open the unit will operate in
Cool mode. If the switch will close the unit will operate in Heat mode.
With the Q8 switch in the Heating position the unit will operate in Heat
mode. Heat setpoints will be used. In case of 4 way valve, the
corresponding solenoid valve will be energized.
