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5121817-TIM-A-0515
Table 19: Additional Static Resistance
Size
CFM
(Tons)
1000
1200
1400
1600
1800
T03 (3.0)
T04 (4.0)
2000
T05 (5.0)
2200
2400
2600
2800
3000
1. Add these values to the available static resistance in the respective Blower Performance Tables.
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.
Operation
Sequence Of Operations Overview
For these units, the thermostat makes a circuit between "R" and
"Y1" for the cooling cycle.
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.
Cooling Sequence Of Operation
Continuous Blower
By setting the room thermostat fan switch to "ON," the supply
air blower will operate continuously.
Intermittent Blower
With the room thermostat fan switch set to "AUTO" and the
system switch set to either the "AUTO" or "HEAT" settings, the
blower is energized whenever a cooling or heating operation is
requested. The blower is energized after any specified delay
associated with the operation.
42
1
Cooling Only
0.08
0.10
0.12
0.14
0.16
0.18
0.20
0.23
0.26
0.29
0.32
2 3
Economizer
0.07
0.08
0.09
0.11
0.13
0.15
0.17
0.20
0.23
0.26
0.30
When energized, the indoor blower has a minimum run time of
30 seconds. Additionally, the indoor blower has a delay of 10
seconds between operations.
No Outdoor Air Options
When the thermostat calls for cooling, the low-voltage control
circuit from "R" to "Y1" and "G" is completed. The compressor
and condenser fan motor are energized. After completing the
specified fan on delay for cooling, the UCB will energize the
blower motor.
Once the thermostat has been satisfied, it will de-energize Y1. If
the compressor has satisfied its minimum run time, the
compressor and condenser fan de-energize. Otherwise, the
unit operates the cooling system until the minimum run time for
the compressor has been completed. After the compressor de-
energizes, the blower is stopped following the elapse of the fan
off delay for cooling.
To be available, a compressor must not be locked-out due to a
high or low-pressure switch or Evaporator Low Limit sensor
detecting a temperature below 26° F and the anti-short cycle
delay (ASCD) must have elapsed.
Reheat Mode Sequence Of Operation
Standard A/C Mode: Input: Y1 On, Y2 Off, Humidistat Open
During normal cooling operation, a Y1 call from the thermostat
will bring on the unit in the standard cooling mode. Since the
humidistat is open, the liquid line solenoid (SLL) will be open
and the hot gas solenoid (SHG) will be closed allowing the unit
to operate in the standard cooling mode.
Reheat Mode: Input: Y1 On, Y2 Off, Humidistat Closed
During reheat mode, the Y1 signal will bring on the compressor
and will send the 24V signal through the humidistat, through the
normally closed contacts of the hot gas relay (RHG) and will
energize both the liquid line and the hot gas solenoids which
2
Electric Heat kW
7 - 15
20 - 30
0.04
0.06
0.05
0.07
0.06
0.08
0.07
0.09
0.08
0.11
0.10
0.13
0.12
0.15
0.14
0.17
0.16
0.20
0.19
0.23
0.22
0.26
Johnson Controls Unitary Products
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