21
Sequence of Operation
The 48XT --A Hybrid Heat unit is designed for installation with a
communicating UI. This unit will not respond to commands
provided by a common thermostat except under certain emergency
situations described in Step 1—Start-- Up and Troubleshooting.
The UI uses temperature, humidity and other data supplied from
indoor and outdoor system components to control heating or
cooling system for optimum comfort. The unit will be commanded
by UI to supply airflow. The unit will operate the indoor blower at
requested airflow for most modes.
INDOOR AIRFLOW ADJUSTMENTS
The nominal requested airflow for heat pump operations will be
350 cfm per ton of nominal cooling capacity as defined by unit
size. Actual airflow request will be adjusted from nominal using
indoor and outdoor temperature and indoor humidity data to
optimize the system operation for occupant comfort and system
efficiency . Refer to UI literature for further system control details.
UNIT OPERATION HAZARD
Failure to follow this caution may result in unit damage.
For cooling operation, the recommended airflow is 350 to
450 cfm for each 12,000 Btuh of rated cooling capacity. For
heating operation, the airflow must produce a temperature
rise that falls within the range stamped on the unit rating
plate.
CAUTION
!
For gas heat operations, Table 3 shows the temperature rise in each
gas heating mode. Refer to these tables to determine the desired
heating airflow for the system being installed.
NOTE: Be sure that all supply--and return--air grilles are open,
free from obstructions, and adjusted properly. Airflow can be
changed using the User Interface. See UI installation instructions
for more detail.
NOTE: Once the compressor has started and then has stopped, it
should not be started again until 4 minutes have elapsed. The
cooling cycle remains “on” until the room temperature drops to
point that is slightly below the cooling control setting of the UI.
HYBRID HEAT SEQUENCE OF OPERATION
The Hybrid Heat sequence of operation, from satisfied to full
heating, is as follows:
The system will attempt to satisfy the call for heat with the first
stage heat pump. There is a ten--minute staging timer before
switching to the second stage heat pump.
Second stage heat pump will run until call for heat is satisfied or
for fifteen minutes. If after 15 minutes the call for heat still exists,
the unit will stage to first stage gas.
For first stage gas the heat pump will be off unless the unit is in
defrost. There is a ten --minute staging timer on first stage gas. If
call for heat still exists after 10 minutes, the system will stage to
second stage gas and run until the call for heat is satisfied.
NOTE: Heat stages are not shortened due to a 5 degree or higher
demand. All stages are utilized for the full allotted time described
above. If the UI determines it is making sufficient progress toward
set point, it may not stage up after the staging timer has elapsed.
Pressing the FAN and TEMPERATURE UP buttons
simultaneously defeats cycle timers. See UI installation instructions
for more detail.
HEAT PUMP SEQUENCE OF OPERATION
COOLING AND HEATING OPERATION
With a call for first stage cooling, the outdoor fan, reversing valve,
and low stage compressor are energized. If low--stage cannot
satisfy cooling demand, high-- stage cooling is energized by the UI.
After second stage is satisfied, the unit returns to low-- stage
operation until first stage is satisfied or until second stage is
required again. When both first stage and second stage cooling are
satisfied, the compressor will shut off. The reversing valve will
remain energized until the control board power is removed or a call
for heating in initiated. With a call for heating, the outdoor fan and
compressor are energized. The compressor will operate in high or
low stage operation, as needed to meet the heating demand. When
the heating demand is satisfied, the compressor and fan will shut
off. The reversing valve is de--energized in the heating mode.
NOTE: When two--stage unit is operating at low-- stage, system
vapor (suction) pressure will be higher than a standard single--stage
system or high--stage operation.
NOTE: Outdoor fan motor will continue to operate for one
minute after compressor shuts off, when outdoor ambient is greater
than or equal to 100°F(38°C).
UTILITY INTERFACE WITH INFINITY CONTROL
The utility curtailment relay should be connected to factory
supplied pigtails (PINK, connected to R, VIOLET connected to Y2
on the control board) located in the low voltage splice box (See
Fig. 14, 15 and 17). This input allows a power utility device to
interrupt compressor operation during peak load periods. When the
utility sends a signal to shut the system down, the UI will display,
“Curtailment Active”.
Table 3 – Air Delivery and Temperature Rise at Rated Heating Input
Unit
Rated Heating Input (Btu/hr) Heating Rise Range
o
F(
o
C) Heating Rise Either Stage, °F(
o
C)
High Stage Low Stage High Stage Low Stage
“Efficiency” “Comfort”
High Stage Low Stage High Stage Low Stage
48XT(--,N)A24040
48XT(--,N)A30040
40,000 26,000
20 -- 50
(11--28)
15--45
(8--25)
35
(19)
30
(17)
40
(22)
35
(19)
48XT(--,N)A30060
48XT(--,N)A36060
48XT(--,N)A42060
60,000 39,000
25 -- 55
(14--31)
25 -- 55
(14--31)
40
(22)
50
(28)
48XT(--,N)A36090
48XT(--,N)A42090
48XT(--,N)A48090
48XT(--,N)A60090
90,000 58,500
35 -- 65
(19--36)
35 -- 65
(19--36)
50
(28)
55
(31)
48XT(--,N)A48115
48XT(--,N)A60115
115,000 75,000
30 -- 60
(17--33)
30 -- 60
(17--33)
45
(25)
50
(28)
48XT(--,N)A48130
48XT(--,N)A60130
130,000 84,500
35 -- 65
(19--36)
35 -- 65
(19--36)
50
(28)
55
(31)
Airfl ow delivery values for external static pressure values of u p to 1 in. wc.
48XT-- A
To Next Page
Loading...
