1101790-UIM-C-0414
Johnson Controls Unitary Products
23
Blower Speed Selection
The variable speed blowers are designed to deliver constant
CFM regardless of the external static pressure (ESP) in the
ductwork. Therefore, if too many supply registers are closed, a
filter becomes clogged, or there is a restriction in the ductwork,
the motor will automatically operate at a higher speed to
compensate for the higher ESP. This may result in a higher
operating sound level.
These units have variable speed motors that automatically adjust
to provide constant CFM from 0.2" to 0.6" w.c. static pressure.
From 0.6" to 1.0" static pressure, CFM is reduced by 2% per 0.1"
increase in static. Operation on duct systems with greater than
1.0" w.c. external static pressure is not recommended.
To Set Cooling CFM for DHQ Units:
Refer to Airflow Performance Tables 13 and 14 for the possible
cooling speed CFM selections.
Set “COOL” and “ADJ” Jumpers on the CFM selection board as
indicated in Tables 13, 14 and Figure 11.
NOTE:
CFM indicator light flashes once for every 100 CFM
(i.e. 12 flashes = 1200 CFM).
To Set Delay Profile:
Every unit has multiple cooling “blower off delay” profiles to
optimize system performance and efficiency. Refer to Table 16
for the regional climate in your area. Place the “DELAY” jumper
tap on the CFM selection board on the appropriate pin setting.
Factory Set Gas Heat CFM:
The blower speed required for gas heat is different than for
cooling. The heating CFM is factory set, but is adjustable.
The “Heat” Jumper on the CFM selection board should be
set to “A” from the factory.
Fan Only CFM:
When the connection is made from “R” to “G”, the fan only
mode is activated. In this mode, the blower will deliver 75% of
the cooling system CFM. This connection is factory set from the
manufacturer, but can be field adjusted.
Figure 11: Control Board Speed Tap Location
Operation
The unit is controlled by a conventional heating/cooling
thermostat common to this class of equipment.
Sequence Of Operation
Heat
First Stage Cooling Call
On a first stage cooling call, the thermostat sends 24 Volts AC
out of the “Y1”, “O”, and “G” terminals to the CFM Selector
Board (CFMCB).
When 24 Volts AC is sent from CFMCB to the “Y1” terminal of
the YorkGuard VI defrost control board (DCB) energizing the
“M1” contactor coil.
When the contactor coil is energized, the compressor operates
in first stage cooling; the “ODF” contacts on the DCB close and
energize the ECM 142R outdoor fan motor in low speed.
Exception: The 2 ton dual fuel units operate the outdoor fan at
high speed anytime the compressor is operating.
24 Volts AC is also sent out of the CFMCB to the ECM Blower
Motor for first stage cooling fan speed and out of the “RV” and
Table 15: Indoor Blower Specifications
Model
(Tons)
Motor
HP
RPM
Eff.
SF
Frame
DHQ
024
(2.0)
1/2
1050
0.8
1.0
48
DHQ
030
(2.5)
3/4
1050
0.8
1.0
48
DHQ
036
(3.0)
3/4
1050
0.8
1.0
48
DHQ
042
(3.5)
1
1050
0.8
1.0
48
DHQ
048
(4.0)
1
1050
0.8
1.0
48
DHQ
060
(5.0)
1
1050
0.8
1.0
48
Do not change the “ADJ” tab position on the CFM
selection board as this will change your cooling CFM
previously selected.
Table 16: Delay Profile
Delay Tap
Regional Climate Type
Jumper at “A”
Standard Setting
Jumper at “B”
Humid Climate
Jumper at “C”
Dry Climate
Jumper at “D”
Temperate Climate
W2
W1
R
Y1
Y/Y2
