VTS Medical Systems VENTUS COMPACT HP VVS021c Instructions For Use Manual page 40

6.4 DIFFERENTIAL PRESSURE SWITCH
The differential pressure switch is another safety element, in addition to the thermostat, which prevents
the heater from operating under unallowable conditions. It prevents the heater from switching on if the
pressure generated by the fan units on the supply side of the air handling unit is insufficient to ensure safe
operation of the heating elements.
!
! The pressure switch is a factory fitted and electrically connected component - the connection of
the pressure switch pressure hoses must be made on site according to the following
instructions:
•
one of
if the switchboard is installed on a duct (outside), the cable does not need to be
connected - there is atmospheric pressure in the switchboard,
•
the second of the hoses should be connected at positive or negative pressure in the air
handling unit or duct (before or after the supply motor),
•
it is permissible to relocate the pressure switch outside the switchboard (in the duct
version of the heater) in order to avoid the need to run long measuring tubes - the
recommended position of the pressure switch is horizontal, in the vertical position the
reading is 11Pa higher than the actual one.
!
! The switching threshold of the pressure switch is 20 Pa. When connected to the AHU, check
that the pressure switch is operating correctly for the smallest available capacity of the air
handling
If no differential pressure is detected, change the connection point of the second pressure
hose to the system.
! In the opposite case - when for a given pressure switch setting the pressure difference is
detected even if the unit is switched off (allowing the heater to operate even if the fans are
not running), the setting should be gradually increased until correct operation is obtained - it is
indicated by the electric heater not operating despite the occurrence of control signals, if the
pressure switch does not detect the pressure difference between the measurement channels -
permission should be given only after the fans are started up.
!
Once the pressure switch is fully connected, the heater shutdown test must be performed.
To do so, force the electric heater control manually (e.g. by providing control signals for the heater
from the controller) and at the same time stop controlling the fans. The pressure switch should
prevent the electric heater from operating (this will be visible e.g. by disconnecting the contactors
in the switchgear).
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the conductors should
OIMM VENTUS COMPACT HP - ver.5.0.9 (10.2024)
be routed to atmospheric pressure -
unit.
40