Filters - Carrier AERO 39MN Installation, Start-Up And Service Instructions Manual

There are additional precautions and control strategies, as
found in various catalogues and in the ASHRAE Fundamen-
tals Handbook and in the Carrier System Design Guide —
Piping Section, when the entering-air temperature to the coil
falls below 35 F. These conditions occur when IDT coils are
used for pre-heat and/or face and bypass applications.
Freeze-up protection:
1. Use a strainer in the supply line and the dirt leg ahead of
the trap.
2. Use a vacuum breaker in the return.
3. Do not use overhead returns from the coil. A floodback
can occur.
4. An immersion thermostat to control outdoor-air damp-
ers and the fan motor is recommended. This control is
activated when the steam supply fails or the condensate
temperature drops below a predetermined temperature,
usually 120 F.
5. On low pressure and vacuum systems, the immersion
thermostat may be replaced by a condensate drain with a
thermal element. This element opens and drains the coil
when the condensate temperature drops below 165 F.
Note the thermal condensate drain is limited to 5 psig
pressure. At greater coil pressures they will not open.
In spite of the precautions listed above, a coil may still
freeze up. An oversize capacity coil, at partial load, with a
modulating steam control valve will occasionally freeze.
Freezing occurs in the 20 F to 35 F range of entering-air tem-
peratures. A better installation would be an undersize coil,
with an on/off control valve with thermostatic control in the
outside air, set at 35 F air temperature, installed downstream
of the first coil; or setting the minimum steam pressure at
5 psig.
See Table 34 for filter data for flat filter section,
Filters —
angle filter section, bag-cartridge filter section, and filter
mixing box section. Filters are field supplied.
Air filters should be inspected regularly and changed when
dirty. Filter life can vary greatly from one unit to another, de-
pending upon the application and the amount of contaminants
in the return and ventilation air entering the air handler. Each
job should be evaluated and maintenance schedules estab-
lished accordingly. At a minimum, the filters should be
changed at the beginning of the cooling and heating seasons.
Although not a direct part of the air handler, outdoor air in-
let screens and/or grilles that may be present should also be
checked regularly and cleaned as necessary. They can easily
become plugged with debris, grease, or other contaminants,
depending upon their location. This reduces the availability
of ventilation air, which can contribute to indoor air quality
problems.
All filter sections use adjustable blank-off plates to close
off any airway area not filled with filter media. Check blank-
off plates to prevent unfiltered air from bypassing the filters.
Blank-off plates must be on door side of unit.
BAG-CARTRIDGE FILTERS — Side loading bag-cartridge
filter section can use either bag or rigid filters, 6-in. to 30-in.
deep, with 7 / -in. header. They will not accept headerless rigid
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filters.

Face loading bag-cartridge filter sections can use either
bag or rigid filters and are loaded from the front of the sec-
tion. These sections use Puro-Frame holding frames located
at the downstream edge of the filter section for prefilters and
bag/cartridge filters. Cartridge filters without headers can ex-
tend upstream of the holding frame by 24 inches. Cartridge
and bag filters with 7 /
filter section with filter length limited only by the length of
the plenum following the filter section. Filter elements are re-
tained in frames by wire fastener clips. To replace filter ele-
ments, remove clips, insert elements with bag or cartridge
downstream and reinstall clips. See Fig. 128.
See Fig. 129 for typical track for bag-cartridge filter sec-
tion used on draw-thru unit.
135
-in. header extend downstream of the
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