NuAire LabGard NU-581-400, Operation And Maintenance Manual

Page: 64 / 107

OM0302
Rev 2/December 2020 Page 64 of 107
A leak is detected when a sustained particle count is over 40 counts per second (for a period of 60 seconds during the
total time of the challenge) above the average unchallenged background particle count.
7.6.2 Supply Filter
The diffuser plate placed below the HEPA to protect the filter during normal usage may be removed as follows:
The diffuser is secured to the cabinet shell by #1/4-20 acorn nuts located immediately behind the front viewing
window. After removing the fasteners, drop the front of the diffuser plate several inches and pull forward gently.
Note that the diffuser is purposely a tight fit - it is held to the back wall of the cabinet interior by a light push - fit
with projecting studs. To avoid the window high alarm during the filter integrity check. It is desirable to enter the
Calibration/Service menu and turn on the blower.
7.6.3 Exhaust Filter
The exhaust filter is typically more difficult to check since protective grills, charcoal filters, or exhaust transitions
could cover the filter. Access panels are usually provided and should be removed. If an air gap exhaust transition
is provided, the air gap must be sealed with duct tape or other suitable means to prevent contaminated air from
migrating into the exhaust efflux. All exhaust blowers/fans should be turned off during the check. The exhaust
sensor shroud can also be removed for the exhaust filter integrity check. Replace the exhaust sensor shroud
immediately after the filter check to assure proper operation.
Air currents in the room can sometimes contribute to exhaust entrainment on top of the cabinet. This can lead to
false leak readings. In order to reduce the probability of false leak readings it is recommended to cover half of the
exhaust HEPA filter while scanning the uncovered section of the exhaust HEPA filter.
NOTE:
To avoid the window high alarm during the filter integrity check, it is desirable to enter into the
calibration/Service/Sensor Setup/calibrate downflow sensor menu.
NOTE: If the upstream challenge port is deemed contaminated and not accessible, use both downflow
and exhaust volume for determining challenge concentrations. Use following area information
below with average downflow velocity and spot-check exhaust velocities as measured to determine
volume (CFM) (CMH).
Model Size *Supply Area (ft 2 )(m 2 ) Exhaust Area (ft 2 )(m 2 )
400 8.53 (.792) 3.06 (.284)
500 10.74 (.998) 4.17 (.387)
600 12.95 (1.203) 5.00 (.465)
* Measured 4 inches above the bottom edge of the window.
Laskin Nozzle Concentration Formula
# Nozzles x 135 CFM x 100 ug/L Challenge
=
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