AAF International PRU - Manual (Page 15)

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3.11 Pressure Gauge: Pressure gauges are installed across the filter
system to indicate when the particulate filters (being the prefilter and
high efficiency filters) need to be replaced. The pressure gauge will
register the pressure differential across each filter bank. As the
particulate filter loads with dirt, the resistance to the airflow, and
consequently, the pressure across the filter will increase. The
pressure across the gas-phase chemical filter(s) will remain constant,
since these filters collect gas molecules and not particulate. Pressure
gauges across the gas-phase filter banks are not supplied as part of
the standard product. The pressure gauges are normally part of the
housing and will be supplied in the installation shown below:
Recirculation Unit (RU) with wall mounted gauges
3.12 Fans: The standard RU is supplied with an internally-mounted
fan. See the AAF submittal drawing and wiring diagram for information
and details.
CAUTION: All electrical work must be carried out in accordance
with all appropriate governing electrical codes and standards.
! WARNING: All electrical work has the potential to cause shock,
injury, and even death. Disconnect all power whenever working on
the system. Only qualified electrical personnel should work on the
fan and control system.
3.12.1 Provide an appropriate power supply as specified in the
submittal information.
CAUTION: Use of the incorrect line voltage may result in
irreparable damage to electrical components.
Step 1: Remove screws holding the fan access panel in place.
Step 2: Remove the panel.
3.12.2 Access to the Fan: Access to the fan section is obtained by
removing the center panel as shown in the following sequence.