Installation and Operating Guide
Smart Pass-Through Chambers
©
Copyright 2017 Terra Universal Inc. All rights reserved. • Revised July 2020 • Document No. 1788-27
Terra Universal, Inc. • TerraUniversal.com • 800 S. Raymond Ave. • Fullerton, CA 92831 • TEL: (714) 578-6000 • FAX: (714) 578-6020
12
3.2
Recirculating Air Showers
The Recirculating Air Shower configuration equips the Smart Pass-through with one of Terra’s fan/filter units. HEPA-filtered air
flows down from the ceiling of the chamber and exits through vents at the bottom of the chamber before circulating back up
through the walls of the pass-through. This recirculating air flow prevents particles from settling and accumulating within the
pass-through chamber, while making the interior air progressively cleaner with each pass over the HEPA filter.
The FFU is controlled using a separate power switch and fan speed dial located on the “dirty” side of the pass-through. When
switched on, the blower can take up to 30 seconds to ramp up to the indicated speed. Increasing the speed of the blower will
increase the number of air exchanges per hour and increase the pressure within the chamber. However, increasing the speed
too much can cause turbulence within the chamber and generate excessive heat from the motor.
A Minihelic gauge displays the pressure differential between the chamber and the external environment in inches of water
column. A typical pressure differential will read as a fraction of an inch of water column (e.g. 0.5” WC), depending on the speed
setting and the remaining life of the HEPA filter.
Turn off both power switches prior to servicing the pass-through. If the unit is equipped with a key-
switch, insert the key and turn it to BYPASS mode to disable the Smart Interlock.
WARNING
HEPA Filter Replacement
The HEPA filter should be replaced if there is a noticeable
reduction in air flow or if a leak is present. Airflow should be
measured with an air speed monitor and FFUs should be tested
periodically to detect these changes.
1.
Remove the metal screen on the ceiling of the chamber to expose
the HEPA filter (See
Figure 17
).
2.
Rotate the clips that hold the filter in place and allow the HEPA
filter to drop out of the housing.
Figure 15:
A stainless steel screen hides the HEPA filter
Figure 16:
Air escapes through the exhaust vents along the
bottom of the chamber
Figure 17:
Exposed filter after removing protective screen
