290699-YIM-B-0607
38
Unitary Products Group
PHASING
Check for proper compressor rotation. If the blower or
compressors rotate in the wrong direction at start-up,
the electrical connection to the unit is misphased.
Change the incoming line connection phasing to obtain
proper rotation. (Scroll compressors operate in only
one direction. If the scroll is drawing low amperage,
has similar suction and discharge pressures, or pro-
ducing a high noise level, the scroll is misphased).
SUPPLY AIR BLOWERS
These blowers have either 3-speed direct drive motors,
or single speed motors equipped with a belt drive. Belt
drive units have a variable pitch pulley that allows the
blower speed to be adjusted.
CHECKING SUPPLY AIR CFM
The RPM of the supply air blower will depend on the
required CFM, the unit accessories or options and the
static resistances of both the supply and the return air
duct systems. With this information, the motor speed
tap (direct drive) or the motor pulley number of turns
open (belt drive) can be determined from the Blower
Performance Data Tables.
Note the following:
1.
The supply air CFM must be within the limitations
shown in the Unit Application Data Table 1.
2.
Pulleys can be adjusted in half turn increments.
3.
The tension on the belt should be adjusted as
shown in the Belt Adjustment Figure 16.
TABLE 26: STATIC RESISTANCES
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
3000
0.07
0.08
0.09
0.11
0.13
0.15
0.17
0.20
0.23
0.26
0.30
7-15KW
0.04
0.05
0.06
0.07
0.08
0.10
0.12
0.14
0.16
0.19
0.22
20-30KW
0.06
0.07
0.08
0.09
0.11
0.13
0.15
0.17
0.20
0.23
0.26
0.06
0.07
0.08
0.09
0.10
0.11
0.12
0.14
0.16
0.19
0.22
0.08
0.10
0.12
0.14
0.16
0.18
0.20
0.23
0.26
0.29
0.32
COOLING ONLY
2
RESISTANCE, IWG
CFM
DESCRIPTION
ECONOMIZER
1 3
BOTTOM DUCT CONNECTIONS
1
ELECTRIC
HEATERS
1
1. Deduct these resistance values from the available external static pressure shown in SUPPLY AIR BLOWER PERFORMANCE Tables.
3. The pressure through the economizer is greater for 100% outdoor air than for 100% return air. If the resistance of the return air
duct system is less than 0.25 IWG, the unit will deliver less CFM during full economizer operation.
2. Add these resistance values to the available static resistance values on SUPPLY AIR BLOWER PERFORMANCE Tables.
Scroll compressors require proper rotation to
operate correctly. Do not change the internal
wiring to make the blower, condenser fans, or
compressor rotate correctly. Change the
incoming power to the main terminal block to
obtain proper rotation.
FIGURE 16 - BELT ADJUSTMENT
Loosen nuts (A) (top and bottom).
Adjust the tension by turning bolt (B).
Never loosen nuts (C) from each other.
Use a belt tension checker to apply a perpendicular force to be one belt at the
midpoint of the span as shown. The deflection force should be applied
until a specific deflection distance of 4mm (5/32") is obtained. To determine
the deflection distance from normal position, use a straight edge from
sheave to sheave as a reference line. The recommended deflection force
is as follows:
1.
2.
3.
4.
PROCEDURE FOR ADJUSTING BELT TENSION:
Tension new belts at the max. deflection force recommended for the belt
section. Check the belt tension at least two times during the first 24 hours of
operation. Any re-tensioning should fall between the min. and max.
deflection force values.
5. After adjusting, re-tighten nuts (A).
*Never Loosen
(A)
(C)*
(B)
SPAN LENGTH
DEFL FORCE
