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8 REGULAR MAINTENANCE ITEMS
8.1 Air Filters
The air lter section is an integral part of the environmental control system, designed within the unit
for easy front accessibility. An initial set of lters are factory installed in the unit. The lters are 4-inch
(100mm) deep, disposable, pleated design, extended-surface, nonwoven, reinforced cotton fabric;
supported and bonded to welded-wire grid; enclosed in cardboard frame design rated not less than
MERV 8 per ASHRAE Std. 52.2. A lter dierential switch for alarm activation is included.
Air lters should be checked on a regular basis and changed when they become dirty. This will ensure
ecient operation of the unit. Spare air lters should be kept in stock as these tend to be a frequently
replaced maintenance item. Air lters may require changing as often as monthly dependent on room or
space conditions. New installations with construction dust will quickly clog lters requiring new lters.
The dap4™ control panel monitors the air lters status. A dirty lter alarm will be enunciated on the
controls display screen. Although the unit may display a dirty lter alarm, this should not be relied on
as the only determinant for replacing air lters. A misadjusted air lter dierential pressure switch may
not give a proper indication of a clogged lter.
To check the air lter pressure dierential pressure switch for proper adjustment, temporarily cover
approximately 75% of the return air opening using heavy cardboard or similar material. The alarm should
energize when 75% of the air is blocked, simulating dirty lters. If the alarm energizes prematurely or
does not energize at all, the pressure switch should be adjusted. All side panels must remain closed
when determining if an adjustment is necessary.
WARNING: Air lters that require changing can restrict airow and create problems such
as coil icing or poor air distribution.
8.2 Fuses
Always replace fuses with those of the equivalent rating with regard to: 1) amperage, 2) voltage, and
3) speed. For instance motors are inductive loads which require time delay fuses. Electric reheat and
humidiers are resistive loads requiring fast acting fuses.
8.3 Electric Reheat
The electric reheat is a nned enclosed, sheath type, fabricated of stainless steel core sheath with
plated ns to withstand moist conditions. The reheat is installed on the air discharge side of the cooling
coil and has three (3) stages. The reheat is capable of maintaining room dry bulb conditions when
the system is calling for dehumidication. The reheat section includes a safety switches to protect the
system from overheating. The low-watt density elements eliminate ionization associated with open air
electric resistance heating.
Heating elements do not normally require maintenance. However, they may accumulate a lm of dust
or dirt when unused for extended periods of time. When energized, the burning debris can create
smoke or an unpleasant odor. To help avoid a problem, periodic cleaning is recommended.
8.4 Humidier
The unit is provided with a self-contained, microprocessor-controlled steam generator type humidier.
The steam generating humidier uses a disposable cylinder with electronic controls. The humidier
discharges pure steam with no material dust carry-over and has a self-regulating automatic ush cycle.
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