518676-BIM-C-0610
Johnson Controls Unitary Products
49
Operation
Cooling Sequence Of Operation
For the ZS series of units, the thermostat makes a circuit
between "R" and "Y1" for the first stage of cooling.
The call is passed to the
Unit Control Board (UCB),
which
then determines whether the requested operation is available
and, if so, which components to energize.
For gas heating, the UCB monitors the "W1" call but does not
handle the operation of the gas furnace. An ignition control
board controls the gas heater operation. For electric heat units,
the UCB passes the call to the electric heater. In both cases,
when the "W1" call is sensed, the indoor air blower is energized
following a specified heating delay.
If at any time a call for both heating and cooling are present, the
heating operation will be performed. If operating, the cooling
system is halted as with a completion of a call for cooling.
Heating always takes priority.
Table 21: Additional Static Resistance
Size
(Tons)
Model
CFM
Cooling Only
1
1. Add these values to the available static resistance in the respective Blower Performance Tables.
Economizer
2
,
3
2. Deduct these values from the available external static pressure shown in the respective Blower Performance Tables.
3. The pressure drop through the economizer is greater for 100% outdoor air than for 100% return air. If the resistance of the return air duct is
less than 0.25 IWG, the unit will deliver less CFM during full economizer operation.
4” Filter
2
Electric Heat kW
9
18
24
36
54
-06 (6.5)
-07 (7.5)
ZS
1900
0.00
0.07
0.10
0.05
0.06
0.07
0.08
0.10
2100
-0.01
0.09
0.11
0.06
0.07
0.08
0.09
0.11
2300
-0.01
0.11
0.12
0.07
0.08
0.09
0.10
0.13
2500
-0.02
0.13
0.14
0.08
0.09
0.10
0.11
0.14
2700
-0.03
0.16
0.15
0.09
0.10
0.12
0.13
0.16
2900
-0.04
0.18
0.16
0.10
0.11
0.13
0.14
0.18
3100
-0.05
0.20
0.18
0.12
0.13
0.15
0.16
0.20
3300
-0.06
0.22
0.19
0.13
0.14
0.17
0.18
0.22
3500
-0.07
0.24
0.20
0.15
0.16
0.19
0.20
0.24
3700
-0.08
0.27
0.21
0.17
0.18
0.21
0.22
0.26
3900
-0.09
0.29
0.23
0.19
0.20
0.23
0.24
0.28
4100
-0.09
0.31
0.24
0.21
0.22
0.25
0.26
0.31
4300
-0.10
0.30
0.25
0.23
0.24
0.28
0.29
0.34
4500
-0.11
0.35
0.26
0.25
0.26
0.30
0.31
0.37
-08 (8.5)
-10 (10)
-12 (12.5)
ZS
1900
0.06
0.02
0.12
0.05
0.06
0.07
0.08
0.10
2100
0.07
0.02
0.13
0.06
0.07
0.08
0.09
0.11
2300
0.08
0.02
0.14
0.07
0.08
0.09
0.10
0.13
2500
0.09
0.02
0.16
0.08
0.09
0.10
0.11
0.14
2700
0.11
0.03
0.17
0.09
0.10
0.12
0.13
0.16
2900
0.12
0.03
0.19
0.10
0.11
0.13
0.14
0.18
3100
0.14
0.03
0.20
0.12
0.13
0.15
0.16
0.20
3300
0.16
0.03
0.22
0.13
0.14
0.17
0.18
0.22
3500
0.18
0.04
0.26
0.15
0.16
0.19
0.20
0.24
3700
0.20
0.04
0.27
0.17
0.18
0.21
0.22
0.26
3900
0.23
0.04
0.29
0.19
0.20
0.23
0.24
0.28
4100
0.25
0.04
0.32
0.21
0.22
0.25
0.26
0.31
4300
0.28
0.05
0.35
0.23
0.24
0.28
0.29
0.34
4500
0.30
0.05
0.38
0.25
0.26
0.30
0.31
0.37
4700
0.33
0.05
0.41
0.28
0.29
0.33
0.34
0.40
4900
0.36
0.05
0.44
0.30
0.31
0.35
0.37
0.43
5100
0.39
0.06
0.47
0.33
0.34
0.38
0.40
0.46
5300
0.42
0.06
0.51
0.35
0.37
0.41
0.43
0.49
5500
0.45
0.06
0.55
0.38
0.40
0.44
0.46
0.53
5700
0.48
0.06
0.58
0.41
0.43
0.47
0.49
0.56
5900
0.52
0.07
0.62
0.44
0.46
0.50
0.53
0.59
6100
0.56
0.07
0.67
0.47
0.49
0.53
0.56
0.62
6300
0.60
0.07
0.71
0.50
0.53
0.56
0.59
0.65
