Table of Contents
Advertisement
5020803-UIM-M-0120
Table 16: Additional Static Resistance
Size (Tons)
CFM
Wet Indoor Coil Economizer
500
0.01
600
0.01
700
0.01
800
0.02
24 (2.0)
900
0.03
1000
0.04
1100
0.05
1200
0.06
700
0.01
800
0.02
900
0.03
30 (2.5)
1000
0.04
1100
0.05
1200
0.06
1300
0.07
700
0.01
800
0.02
900
0.03
1000
0.04
36 (3.0)
1100
0.05
1200
0.06
1300
0.07
1400
0.08
1100
0.02
1200
0.03
1300
0.04
1400
0.05
1500
0.06
42 (3.5)
1600
0.07
1700
0.07
1800
0.08
1900
0.09
2000
0.09
1100
0.02
1200
0.03
1300
0.04
1400
0.05
1500
0.06
48 (4.0)
1600
0.07
1700
0.07
1800
0.08
1900
0.09
2000
0.09
1100
0.02
1200
0.03
1300
0.04
1400
0.05
1500
0.06
60 (5.0)
1600
0.07
1700
0.07
1800
0.08
1900
0.09
2000
0.09
1. 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.
Note: Filter pressure drop based on standard filter media tested at velocities not
to exceed 300 ft/min.
16
SECTION VI: OPERATION
The following sequences of operation are based on using a single-
1
Filter/Frame Kit
stage heat pump thermostat.
0.00
0.01
COOLING SEQUENCE OF OPERATION
0.00
0.02
0.00
0.04
1. When the fan switch on the thermostat is in the "ON" position, the 24
0.01
0.06
0.01
0.08
0.01
0.10
0.01
0.13
2. On a call for cooling, the thermostat sends 24 V to "Y" and "O" to
0.02
0.16
0.00
0.04
0.01
0.06
0.01
0.08
0.01
0.10
0.01
0.13
3. When the demand for cooling has been satisfied, the 24 V "Y" sig-
0.02
0.16
0.03
0.17
0.00
0.04
0.01
0.06
HEATING SEQUENCE OF OPERATION
0.01
0.08
1. When the fan switch on the thermostat is in the "ON" position, the 24
0.01
0.10
0.01
0.13
0.02
0.16
0.03
0.17
2. On a call for heating, the thermostat sends 24 V to "Y" on the
0.04
0.18
0.02
0.04
0.02
0.04
0.02
0.05
0.03
0.05
3. For units equipped with supplementary electric heat, when the heat
0.04
0.06
0.04
0.07
0.04
0.08
0.04
0.09
0.05
0.10
4. When the heating demand is satisfied, the electric heat is de-ener-
0.05
0.11
0.02
0.04
0.02
0.04
0.02
0.05
0.03
0.05
See Table 15 for more information.
0.04
0.06
DEFROST OPERATION
0.04
0.07
The demand defrost control implements a temperature differential
0.04
0.08
("delta-T") demand defrost algorithm. The heat pump is allowed to oper-
0.04
0.09
ate in the heating mode until the combination of outdoor ambient and
0.05
0.10
outdoor coil temperatures indicate that defrosting is necessary. When
0.05
0.11
coil temperature is below the initiate point for the ambient temperature
continuously for 4-1/2 min, the heat pump is put into a defrost cycle.
0.02
0.04
This 4-1/2 min timer eliminates unnecessary defrost cycles caused by
0.02
0.04
refrigeration surges such as those that occur at the start of a heating
0.02
0.05
cycle.
0.03
0.05
A timed inhibit feature prevents the system from responding to a call for
0.04
0.06
defrost less than 40 min after the initiation of the previous defrost. After
0.04
0.07
the 40 min inhibit time has expired, temperature conditions must call for
0.04
0.08
defrost continuously for 4-1/2 min before a defrost cycle is initiated. A
temperature inhibit feature prohibits defrost if the coil temperature is
0.04
0.09
above 40°F.
0.05
0.10
A forced-defrost feature puts the system into a defrost period every 6 h
0.05
0.11
and 4 min of accumulated compressor run-time to recirculate lubricants,
unless the coil temperature is above 40°F and the ambient temperature
is above 50°F. All defrost timing occurs only while the compressor is on.
V at "G" will bring on the indoor blower motor at the selected airflow.
When the fan switch on the thermostat is in the "AUTO" position, the
blower operates only when there is a call for cooling or heating by the
thermostat.
the defrost control board. The reversing valve solenoid is ener-
gized, and after the anti-short cycle period is complete contactor
coil M is energized. Power is supplied to the compressor and out-
door fan motor, and the reversing valve switched to the cooling
position. When the fan switch on the thermostat is in the "AUTO"
position the indoor blower motor is energized at the YSPD airflow.
nal is removed, and the M contactor is de-energized. When the fan
switch on the thermostat is in the "ON" position, the indoor blower
motor continues to run at GSPD. If the fan switch is in the "AUTO"
position, the indoor motor ramps down after a 60 s delay.
V at "G" brings on the indoor blower motor at the GSPD. When the
fan switch on the thermostat is in the "AUTO" position, the blower
operates when there is a call for heating by the thermostat.
defrost control board. After the anti-short cycle period is complete,
the 24 V signal energizes contactor coil M and power is supplied to
the compressor and outdoor fan motor. The reversing valve
remains in the heating position. When the fan switch on the thermo-
stat is in the "AUTO" position, the indoor blower is energized at the
YSPD.
pump cannot meet the demand, the thermostat "W" sends 24 V.
This signal is sent through the defrost control terminals "W" to
"Wout" an energizes the WSPD. The 24 V signal energizes 1st
stage of electric heat.
gized when the 24 V "W" signal is removed, and the M contactor is
de-energized when the 24 V "Y" signal is removed. When the fan
switch on the thermostat is in the "ON" position, the indoor blower
continues to run. When the fan switch is in the "AUTO" position, the
indoor blower motor ramps down after a 60 s delay.
Johnson Controls Ducted Systems
Advertisement
Table of Contents
