Minihelic Gage; Filters; Bag-Cartridge Filters - Carrier Aero 39MN Series Installation, Start-Up And Service Instructions Manual

Section, when the entering-air temperature to the coil falls be-
low 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 flood-
back 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 conden-
sate temperature drops below a predetermined tem-
perature, 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.
The Minihelic gage is a pressure gage
Minihelic Gage —
that is a selectable option in AHUBuilder
personnel the ability to view the pressure drop across flat and
angled filters, which gives an indication of filter integrity. See
Fig. 177 for a picture of a typical Minihelic gage.
.5
0
INCHES W.C. INCHES W.C.
Fig. 177 — Typical Minihelic Gage
This gage is calibrated and zeroed in the vertical position at
the factory. If the gage is used in any other position, it must be
re-zeroed each time the position is changed. Gages with ranges
under 5 inches w.c. (1.24 kPa), or the equivalent, should be
used only in the vertical position.
If the Minihelic needs to be removed or replaced, after in-
stallation, the gage may need to be zeroed before placing in op-
eration. If re-zeroing is required, firmly hold the case of gage
with one hand and unscrew the front cover with the palm of the
other hand in a counterclockwise direction. If difficult to loos-
en, place a small sheet of rubber between the cover and the
. It gives job site
®
1.0
1.5
2.0
palm of the hand. Zero-adjust screw is located behind the scale
at the pair marked "zero." Use a hex allen wrench and adjust
until pointer is on zero. This must be done with both pressure
connections vented to atmosphere and the gage oriented in the
final mounting position. Replace cover.
Attempted field repair may void your warranty. Recalibra-
tion or repair by the user is not recommended.
CALIBRATION CHECK — Select a second gage or ma-
nometer of known accuracy and in an appropriate range. Use
short lengths of rubber or vinyl tubing to connect the high-pres-
sure side of the Minihelic gage and the test gage to two legs of
a tee. Very slowly, apply pressure through the third leg. Allow
enough time for pressure to equalize throughout the system and
for fluid to drain. If a manometer is being used. Compare read-
ings. If the gage being tested exceeds rated accuracy, it should
be returned to the factory for recalibration.
MAINTENANCE — No lubrication or periodic servicing is
required. Keep case exterior and cover clean. Occasionally, dis-
connect pressure lines to vent both sides of the gage to atmo-
sphere and re-zero the gage.
See Table 45 for filter data for flat filter section,
Filters —
angle filter section, bag-cartridge filter section, and filter mix-
ing 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 established
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 inlet
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, de-
pending upon their location. This reduces the availability of
ventilation air, which can contribute to indoor air quality prob-
lems.
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
tridge filter section can use either bag or rigid filters, 6-in. to
30-in. deep, with 7 / -in. header. They will not accept headerless
8
rigid filters.
Face loading bag-cartridge filter sections can use either bag
or rigid filters and are loaded from the front of the section.
These sections use Puro* Frame holding frames located at the
downstream edge of the filter section for prefilters and bag/car-
tridge filters. Cartridge filters without headers can extend up-
stream of the holding frame by 24 inches. Cartridge and bag
filters with / -in. header extend downstream of the filter sec-
7
8
tion with filter length limited only by the length of the plenum
following the filter section. Filter elements are retained in
frames by wire fastener clips. To replace filter elements, re-
move clips, insert elements with bag or cartridge downstream
and reinstall clips. See Fig. 178.
See Fig. 179 for typical track for bag-cartridge filter section
used on draw-thru unit.
*Registered trademark of Purolator.
190
CAUTION
loading bag-car-