The Trenton air handler blower section is a matched
assembly combining advanced engineering techniques
with the finest materials available.
Large diameter forward-curved centrifugal fans were
designed specifically to operate at low tip-speeds with
minimum power consumption. Fan ratings are based on
tests conducted in accordance with AMCA test code
210. To meet the low noise level requirements of comfort
air conditioning, fan outlet velocities have been reduced
without sacrificing good fan performance. Both wheels
and housings are fabricated of continuous galvanized steel
to insure long troublefree service. Each fan wheel is
individually balanced electronically, and the entire fan
section is rechecked for dynamic balance after unit
assembly.
The fan section is complete with a rugged drive assembly.
The heavy duty motor base is designed for quick and
simple belt adjustment. Each drive combination is
selected for 210% overload based on motor horsepower.
All drives are furnished with matched V-belts. All variable
drive combinations are selected with a total adjustment
range of approximately 20%. The fan shaft is cone-drilled
for tachometer reading through an opening in the belt
guard.
For maximum durability, the entire cabinet assembly is
fabricated of continuous galvanized steel. This heavy
protective finish is maintained intact, completely
undisturbed and is complimented with the use of
corrosion resistant permanent fasteners. The positive
fastening principle of a permanent fastener provides the
rigidity and stability necessary for lifetime performance.
These exclusive Trenton construction features offer you
the ultimate in air handling design.
SOLID STEEL SHAFT WITH LIFETIME BEARINGS
All shafts are of uniform diameter, ground and polished
solid steel. Shaft sizes are selected to perform well
below first critical speed. Trouble free service with
minimum noise level is the quality specification for the
bearings on the Trenton air handlers. Flanged and pillow
block type, are located for proper balance and vibration
free operation. Bearings are self aligning ball type.
Extended lubrication lines are standard.
EXCLUSIVE STEEL FRAME CONSTRUCTION
Sectionalized construction provides complete flexibflity of
unit arrangements with each individual section structurally
designed to provide the absolute maximum in unit
strength and rigidity.
All air handling units feature the extremely rugged Steel
Frame assembly. All static and dynamic forces are
directly transmitted to the unit framework. The bearings
are supported entirely by rigid frame members, eliminating
all dynamic forces from the casing panel. This design
removes all possibility of increased unit vibration caused
by panel mounted bearings.
FACE AND BY-PASS DAMPERS,
( MODELS 214 THRU 164)
The damper section and blades are fabricated of
continuous galvanized steel with the damper rods rotating
MODELS 141 - 150 - 164
in frictionless nylon bushings. Damper shaft extensions
are supplied on both ends to facilitate damper motor
location.
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COIL INFORMATION
With the variety of coil sizes and types available for
mounting in factory fabricated units it is important to
follow a few general guidelines. Besides coil section
space and unit arrangement configuration limitations,
outlined below, care should be taken that all coils
mounted in the same section have identical face
dimensions. All coils by-passed with internal face and
by-pass damper sections must be of small face area.
The maximum coil space available in standard coil
sections is as follows:
Heating Coil Section - 1 Through 4 Row...........= 6 3/4"
The table below lists the depth dimension of the various
types and rows of coils. All dimensions are overall casing
depth. In order for the coils selected on a specific unit to
fit in a standard coil section, the sum of depth dimensions
of the coils in series must not exceed the maximum
space available.
Draw-Thru unit sizes 237 with medium or small face area
cooling coils and 141 with small face area cooling coils
are not equipped with the intermediate drain trough. For
this reason, the maximum space available with these
units may be increased by 2-3/4".
Selection of cooling & heating coils may be made from
current Trenton Refrigeration cataloged data.
DIRECT EXPANSION
COIL (TDX)
Heating coil in reheat position with
internal by-pass of cooling coil only.
Cooling coil space consumed may not
exceed 9 5/8”. Heating coils need not
be same face area as cooling coil.
(Face and By-Pass Dampers not
available on models 103 thru 111).
Heating coil in reheat position.
Heating coil must be small face area
and cooling coil space consumed may
not exceed 9 5/8”.
Heating coil in reheat position with
internal face and by-pass of cooling coil
only. All coils must be small face area.
(Not available on Models 103 thru 111).
WATER HEATING &
COOLING COILS
(TWS, TWD, TWH)
Heating coil in preheat position with
internal by-pass of cooling coil.
Cooling coil must be small face area.
Heating coil may be large, medium or small
face area. For proper air distribution space is
required between the heating coil and the internal face
and by-pass damper section. An access section may be
used for this purpose. (Face and by-pass Dampers not
available on Models 103 thru 111).
GENERAL - Certain basic factors must be predetermined
prior to the selection of a central station air handler. The
factors which will control the unit selection are applicable
codes, ventilation requirements. heating and cooling
space loads, acceptable temperature differentials, thermal
media and installation limitations. The selection of the
unit can then be resolved to five steps: (1) Unit type and
size, (2) Cooling coil, (3) Heating coil, (4) Accessories
and, (5) Motor size.
SELECTION OF UNIT TYPE AND SIZE - With the overall
system designed to minimize the number of units and the
heating, cooling and ventilation requirements for the
various zones established, selection of the optimum unit
size can be made based on the required air volume. The
heating load, cooling load and ventilation requirement will
establish a cfm need, any one of which may be the
maximum.
The unit air volume for cooling is dependent upon the
sensible space cooling load and the design dry bulb
temperature differential. Normal temperature differentials
for air conditioning are from 12 to 25 degrees °F. The
minimum air volume is calculated using the following
formula:
Normal temperaturedifferentials for heating are from 20 to
50 degrees °F. The required minimum air volume for
heating calculated using the same formula.
The required air volume for ventilation is generally less
than that for cooling or heating. However, where toxic
fumes or unusual contaminants are encountered, the
ventilation requirements may establish a minimum air
volume in excess of that determined for cooling or heating.
The unit size can then be selected based on maximum air
volume required. Usually more than one unit size can be
selected to deliver the required air. Therefore, fan outlet
velocity, coil face velocity, fan rpm and bhp should also be
given consideration in the final selection. The fan
performance tables are conveniently arranged with cfm,
fan outlet velocity, coil face velocity, fan rpm and bhp in
tabular form for simple selection of the optimum unit size.
SELECTION OF COILS - Having determined the unit size,
the selection of the coil is resolved to three steps:
(1)Choice of the face area coil for optimum face
(2)Choice of the type of coil suited to the application,
(3)Determination of number of rows and fin series.
Cfm =
velocity,
and
Sensible Space Load (Btuh)
1.09 x Temp. Differential
COOLING COIL - The coil size should be selected for
maximum face velocity to obtain peak heat transfer
efficiency and minimum cost. Generally 500 to 600 fpm
is considered the optimum coil face velocity range for
dehumidification application.
Determination of the number of rows and fin spacing is
made using the current Trenton cooling coil
catalogues.
HEATING COIL - Selection of the heating coil is a
choice of coil type, size and determination of the
required number of rows and fin spacing.
Determination of the number of rows and fin spacing is
made from the current Trenton Heating Coil
Catalogs.
SELECTION OF ACCESSORIES - Accessories should
be selected to provide a complete air conditioner with
proper cleaning, mixing and control of the air. Trenton
offers a complete line of accessories to simplify the
selection and installation of accessories.
AIR CLEANING - A filter section should be selected to
provide filter area such that the filter velocity will be
compatible with the choice of filter media. Trenton offers
two filter sections; flat, and angular, for units 214 thru
164. Units 103 thru 111 use flat only.
AIR MIXING - Mixing dampers are included as a simple
means of introducing outside air with thorough mixing
and proportional control of the recirculated and fresh air.
A mixing box is available for each unit size and is also
offered in combination with the angular filter section.
TEMPERATURE CONTROL - Dampers are often
selected as an effective means of temperature control
because they offer close control without time lag. Face
and by-pass dampers are available for units 214 thru
164. The face and by-pass dampers are available with
an internal by-pass duct (used with small face area coils
only) or with an external by-pass duct.
SELECTION OF FAN MOTOR - The determination of
the actual fan performance requires an accurate
calculation of the resistance to air flow thru the entire
system. This total resistance consists of two parts. the
external static pressure of the distribution system, and
the internal unit resistance.
The internal unit resistance is found by summing the
resistances of the coils, various unit components and
accessories. Components resistances are tabulated in
Table 2.
- 4 -
FAN PERFORMANCE
DETERMINATION OF FAN SPEED AND MOTOR HP
REQUIREMENTS
Final determination of the actual fan performance
requires an accurate calculation of the total resistance
to air flow through the entire system. This total static
pressure (TSP) will consist of two parts: (1 ) the external
resistance due to air flow through the ducts, discharge
grilles, diffusers, etc. of the distribution system, and (2)
the internal resistance of the unit which results from air
flow through the coils, filters, unit cabinet and other
accessories. The method of calculating the resistance
for the various components of the distribution system
are well established. The internal resistances are easily
determined from Table 2 which tabulates the resistance
values for the various unit components in increments of
air volume. To the internal resistances as shown in
Table 2, the resistances of the cooling and heating coils
must be added. These may be obtained from the
Trenton cooling and heating coil catalogs.
After calculating the total static pressure, the fan speed
and motor horsepower requirements can be accurately
determined. With the unit model, cfm and TSP known,
the fan rpm and bhp is easily determined from the Fan
Performance Tables.
FAN PERFORMANCEINFORMATION
This catalog contains all of the fan performance tables
for the Trenton central station air handlers.
Low pressure Air Conditioners and low pressure Heating
and Ventilating units are equipped with forwardly curved
fan wheels as standard.
Further pressure loss correction is required for vertical
draw-thru Trenton central station air conditioners, by
adding the casing air pressure drop found in Table 2,
”Component Air Friction”.
SELECTION RULES - The fan performance calculation
procedure is predicated on the fact that a fan is a
constant volume machine, provided the rpm and static
pressure do not change. This means the delivered air
volume (CFM) will not change, even though the
temperature may. The bhp required is inversely
proportional to final air temperature and altitude;
consequently bhp decreases with an increase in final air
temperature or higher altitude and increases with a
decrease in final air temperature or lower altitude. This
requires that the static pressure be adjusted for any air
conditions other than standard. After the calculation of
rpm and bhp, only the bhp need be corrected to the
specified conditions.
SELECTION PROCEDURE - The following data is required
to determine the fan performance. The unit type, unit
size, CFM, total static pressure, operating temperature
and altitude.
1.From Table 1, obtain the temperature and altitude
conversion factor.
2.Divide the specified total static pressure by the
conversion factor to obtain a corrected total static
pressure.
3.At the specified CFM and corrected total static
pressure, determine the rpm and bhp.
4.Multiply the bhp by the conversion factor to obtain
the bhp required at the specified attitude and
temperature.