Installation manual

035-16682-000-E-0303
Unitary Products Group 63
SUPPLY AIR DRIVE ADJUSTMENT
At unit start-up the measured CFM based on Figures 58 and
59 may be higher or lower than the specified CFM. To
achieve the specified CFM, the speed of the drive may have
to be decreased or increased by changing the pitch diameter
(PD) of the motor sheave as outlined below:
• (Specified CFM/Measured CFM) X PD of standard
sheave = PD of new sheave.
Use the following tables and the PD calculated per the above
equation to select a new motor sheave.
EXAMPLE
• A 30 ton unit was selected to deliver 12,000 CFM with a
20 HP motor and a 966 RPM drive, but the unit is only
delivering 11,000 CFM per Table 30.
• Use the equation to determine the required PD for the
new motor sheave (12,000 CFM/11,000 CFM X 6.9” =
7.53 inch).
• Use the 30 ton Table 35.To select a Browning 2B5V74
which will increase the speed of the unit’s drive and its
supply air CFM 108.7%.
• New drive speed = 1.087 X 966 = 1,050 RPM
• New supply air = 1.087 X 11,000 = 11,957 CFM
• Re-use the existing belts and blower sheave.
.
New motor BHP = (speed increase) 3 X estimated motor BHP
to original start-up with 11,000 CFM and 966 RPM = (1.087)
3
X 13.5BHP = 1.284 X 13.5 BHP = 17.3 BHP New motor amps
= (speed increase)
3
X measured motor amps at original start-
up with 11,000 CFM and 966 RPM.
SYSTEM SETPOINTS
The following setpoints must be field adjusted prior to starting
the unit (Refer to Table 33).
CONSTANT VOLUME UNITS (CV)
T7300 THERMOSTAT: cooling/heating setpoints and time
schedule.
OPTIONAL ECONOMIZER: economizer setpoint and mini-
mum position adjustment. (See page 18 Economizer Set
Point Adjustment).
OPTIONAL BUILDING STATIC PRESSURE CONTROL
(exhaust static pressure control): building setpoint.
Before making any blower speed changes review
the installation for any installation errors, leaks or
undesirable systems effects that can result in loss
of air flow.
Even small changes in blower speed can result in
substantial changes in static pressure and BHP.
BHP or AMP draw of the blower motor will
increase (see table 32) by the cube ratio of the
blower speed. Static pressure will increase by the
square ratio of the blower speed. Tables 24 and 25
are for reference only. All blower speed changes
must be made by qualified personnel with strict
adherence to the fan laws.
TABLE 32: BLOWER SPEED RATE OF CHANGE
CHANGE IN RPM
CHANGE IN
CFM TSP
BHP AND
MOTOR
AMPS
.90 .90 .81 .73
.93 .93 .86 .79
.95 .95 .90 .86
.98 .98 .95 .93
1.00 1.00 1.00 1.00
1.03 1.03 1.05 1.08
1.05 1.05 1.10 1.16
1.08 1.08 1.16 1.24
1.10 1.10 1.21 1.33
1.13 1.13 1.27 1.42
1.15 1.15 1.32 1.52
1.18 1.18 1.38 1.62
1.20 1.20 1.44 1.73