Modine Manufacturing PV Installation And Service Manual page 9

I I N N S S T T A A L L L L A A T T I I O O N N
I I n n s s t t a a l l l l a a t t i i o o n n o o f f B B l l o o w w e e r r M M o o d d e e l l s s ( ( B B V V U U N N I I T T S S ) )
D D e e t t e e r r m m i i n n i i n n g g B B l l o o w w e e r r S S p p e e e e d d
The drive assembly and motor on all gas-fired blower unit
heaters are factory assembled. The adjustable motor sheave
has been pre-set to provide the highest CFM at the lowest static
pressure the drive can be used (see pages 16 & 17). The motor
sheave should be adjusted as required when the unit is to be
operated at other conditions. Adjustment must always be within
the range shown in the performance data tables for blower unit
heaters, and the temperature rise range shown on the unit's
rating plate.
To determine the proper blower speed and motor sheave turns
open, the conditions under which the unit is to operate must be
known. If the blower unit is to be used without duct work,
nozzles or filters, the only criteria for determining the motor
sheave turns open and blower speed is the amount of air to be
delivered. The performance data tables for blower models are
shown on pages 16 and 17. As an example, a model BV350
unit, operating with no external static pressure, that is, no duct
work, nozzles, etc., and is to deliver an air volume of 6481 cfm
(cfm = cubic feet of air per minute) requires that the unit be
supplied with a 5 hp motor, a C116 drive, and the drive pulley
must be set at 2.5 turns open to achieve a blower speed of 970
rpm. See "Blower Adjustments" on page 10 for setting of motor
sheave turns open.
If a blower unit is to be used with ductwork or nozzles, etc., the
total external static pressure under which the unit is to operate,
and the required air flow must be known before the unit can be
properly adjusted. Any device added externally to the unit, and
which the air must pass through, causes a resistance to air flow.
This resistance is called pressure loss. The total of the pressure
losses must be determined before adjusting the blower speed.
If Modine filters are used, the expected pressure loss through
the filters is given in the filter table on page 17. If Modine
supplied discharge nozzles are used, the expected pressure
drop of the nozzles can be found footnoted at the bottom of
page 14. If filters, nozzles or ductwork are to be used with the
unit, and they are not supplied by Modine, the design engineer
or installing contractor must determine the pressure loss for the
externally added devices or ductwork to arrive at the total
external static pressure under which the unit is to operate.
Once the total static pressure and the required air flow are
known, the operating speed of the blower can be determined
and the correct motor sheave adjustments made. As an
example, let's say, a model BV350 is to be used with a Modine
supplied blower enclosure and Modine supplied filters attached
to someone else's ductwork. The unit is to move 6481 cfm or air
flow against an external static pressure of 0.2" W.C. Also, you
must add 0.2" W.C. for the filter pressure drop for a total of 0.4"
W.C. total pressure drop. Entering the performance table on
page 16 for a BV350, at 6481 cfm and 0.4" W.C. static
pressure, it is seen that the unit will require a 5 hp motor using a
C116 drive, and the motor sheave should be set at .5 turns
open to achieve a blower speed of 1060 rpm. You can see this
example differs from similar conditions in paragraph 2 by the
number of turns open and a higher rpm, which is needed to
overcome the added external static pressure from the filters.
T T o o I I n n s s t t a a l l l l ( ( F F i i g g u u r r e e 5 5 ) )
1. Remove and discard the motor tie down strap and the
shipping block beneath the belt tension adjusting screw
(Not used on all models.)
F F i i g g u u r r e e 5 5
M M a a i i n n B B l l o o w w e e r r U U n n i i t t H H e e a a t t e e r r C C o o m m p p o o n n e e n n t t s s
THREADED MOUNTING BRACKETS ON
BLOWER ASSEMBLY
BLOWER
SHEAVE
BLOWER
HOUSING
2. Adjust motor adjusting screw for a belt deflection of
approximately 3/4" with five pounds of force applied midway
between the sheaves (refer to Figure 6a). Since the belt
tension will decrease dramatically after an initial run-in
period, it is necessary to periodically re-check the tension.
Excessive tension will cause bearing wear and noise.
3. The blower bearings are lubricated for life; however, before
initial unit operation the blower shaft should be lubricated at
the bearings with SAE 20 oil. This will reduce initial friction
and start the plastic lubricant flowing.
4. Make electrical connections according to the wiring
diagram.
5. Check rotation of the blower. Motor should be in clockwise
rotation when facing motor sheave. If rotation is incorrect,
correction should be made by interchanging wiring within
the motor. See wiring diagram on the motor.
6. The actual current draw of the motor should be determined.
Under no condition should the current draw exceed that
shown on the motor rating plate.
7. It is the installers responsibility to adjust the motor sheave
to provide the specified blower performance as listed on
pages 16 & 17 for blower settings different from the factory
set performance. The drive number on the unit may be
identified by referring to the Power Code number on the
serial plate of the unit (see page 27 for model number
nomenclature) and matching that number with those shown
on page 18. From the listing, the drive number can be
determined.
8. Blower sheave and motor sheave should be measured to
assure correct drive is on unit. Refer to page 19 for drive
sizes.
MOTOR MOUNTING
BRACKET
MOTOR SHEAVE
(MOVEABLE
FACE TO
MOTOR
OUTSIDE)
ADJUSTMENT
SCREW
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