5725848-XIM-A-0319
Johnson Controls Ducted Systems 35
Phasing
YORK MODEL ZF units are properly phased at the factory.
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 producing 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 airflow rate
The RPM of the supply air blower will depend on the required
Volumetric Flow Rate, 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.
Table 19: Belt drive motor and drive data
MODEL
BLOWER
RANGE (RPM)
MOTOR
1
ADJUSTABLE MOTOR PULLY FIXED BLOWER PULLY BELT
HP RPM
FRAME
SIZE
SERVICE
FACTOR
DESIG-
NATION
PITCH DIA. BORE PITCH DIA. BORE
PITCH
LENGTH
DESIG-
NATION
mm inch mm inch mm inch mm inch mm inch
5 TON 812-1102 1.5 1450 56 1.0 IVL44 69-97 2.8-3.8 22 7/8 127 5.0 25 1 922 36.3 A35
6 TON 948-1227 1.5 1450 56 1.0 IVM50 86-112 3.4-4.4 22 7/8 132 5.2 25 1 947 37.3A36
1. All motors have solid bases and are inherently protected. These motors can be selected to operate into their service factor because they
are located in the moving air, upstream of any heating device.
Table 20: Static resistances
DESCRIPTION
RESISTANCE, Pa
M
3
/S
0.47 0.57 0.66 0.75 0.85 0.94 1.03 1.13 1.23 1.32 1.42
ECONOMIZER
1,2
17.4 19.8 22.3 27.3 32.2 37.2 42.2 49.6 57.0 64.5 74.4
ELECTRIC HEATERS
1
7-15KW 10.0 12.4 14.9 17.4 19.8 24.8 29.8 34.7 39.7 47.1 54.6
20-30KW 14.9 17.4 19.8 22.3 27.3 32.2 37.2 42.2 49.6 57.0 64.5
BOTTOM DUCT CONNECTIONS
1
14.9 17.4 19.8 22.3 24.8 27.3 29.8 34.7 39.7 47.1 54.6
COOLING ONLY
3
19.8 25.0 29.8 34.7 39.7 44.6 49.6 57.0 64.5 71.9 79.4
DESCRIPTION
RESISTANCE, IWG
CFM
1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000
ECONOMIZER
1,2
0.07 0.08 0.09 0.11 0.13 0.15 0.17 0.20 0.23 0.26 0.30
ELECTRIC HEATERS
1
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
BOTTOM DUCT CONNECTIONS
1
0.06 0.07 0.08 0.09 0.10 0.11 0.12 0.14 0.16 0.19 0.22
COOLING ONLY
3
0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.23 0.26 0.29 0.32
1. Deduct these resistance values from the available external static pressure shown in SUPPLY AIR BLOWER PERFORMANCE Tables.
2. 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 62.0 Pa [0.25 IWG], the unit will deliver less M3/S or CFM during full economizer operation.
3. Add these resistance values to the available static resistance values on SUPPLY AIR BLOWER PERFORMANCE Tables.
Scroll compressors require proper rotation to operate
correctly. Units are properly phased at the factory. Do
not change the internal wiring to make the blower,
condenser fans, or compressor rotate correctly.
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