N4H7T: Installation Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
7
Airflow Selection for FV4C Fan Coils
(non-communicating)
The FV4C provides high- and low-stage blower operation to match the
capacities of the compressor at high- and low-stage.
To select recommended airflow, refer to the FV4C Installation
Instructions. The FV4C utilizes an Easy Select control board that allows
the installing technician to select proper airflows. This fan coil has an
adjustable blower-off delay factory set at 90 sec. for high- and low-stage
blower operation.
Start-Up
Follow these steps to properly start up system:
1. After system is evacuated, fully open liquid and vapor service
valves.
2. Unit is shipped with valve stem(s) front seated (closed) and caps
installed. Replace stem caps after system is opened to refrigerant
flow (back seated). Replace caps finger-tight and tighten with
wrench an additional 1/12 turn.
3. Close electrical disconnects to energize system.
4. Set room thermostat at desired temperature. Be sure set point is
below indoor ambient temperature.
5. Set room thermostat to HEAT or COOL and fan control to ON or
AUTO mode, as desired. Operate unit for 15 minutes. Check
system refrigerant charge.
Sequence of Operation
NOTE:
Defrost control board is equipped with 5 minute lockout timer
that is initiated upon any interruption of power.
Turn on power to indoor and outdoor units. Transformer is energized.
These models utilize a 2-stage indoor thermostat. With a call for first
(low) stage cooling or heating, the outdoor fan and low-stage
compressor are energized. If low-stage cannot satisfy cooling or heating
demand, high-stage is energized by the second (high) stage of the indoor
thermostat. After the second stage is satisfied, the unit returns to
low-stage operation until second stage is required again. When both,
first and second stage cooling or heating are satisfied, the compressor
will shut off.
Cooling
With first stage cooling, Y1 and O are powered on; and with second
stage cooling, Y2, Y1 and O are powered on. The O energizes the
reversing valve, switching it to cooling position. The Y1 signal sends
low voltage through the safeties and energizes the T1 terminal on the
circuit board. If the compressor has been off for 5 minutes, or power has
not been cycled for 5 minutes, the OF2 relay and T2 terminal will
energize. This will close the contactor and start the outdoor fan motor
and compressor. When the cycle is complete, Y1 is turned off, stopping
the compressor and outdoor fan. The 5 minute time guard begins
counting. Compressor will not come on until this delay expires. In the
event of a power interruption, the time guard will not allow another
cycle for 5 minutes.
Heating
With first stage heating, Y1 is powered on; with second stage heating,
Y2 and Y1 are powered on. The Y1 signal sends low voltage through
the safeties and energizes the T1 terminal on the circuit board. If the
compressor has been off for 5 minutes or power has not been cycled for
5 minutes, the OF2 relay and T2 terminal will energize. This will close
the contactor and start the outdoor fan motor and compressor.
When the cycle is complete, Y1 is turned off, stopping the compressor
and outdoor fan. The 5 minute time guard begins counting. Compressor
will not come on until this delay expires. In the event of a power
interruption, the time guard will not allow another cycle for 5 minutes.
Compressor Operation
The basic scroll design has been modified with the addition of an
internal unloading mechanism that opens a by-pass port in the first
compression pocket, effectively reducing the displacement of the scroll.
The opening and closing of the by-pass port is controlled by an internal
electrically operated solenoid. The modulated scroll uses a single step of
unloading to go from full capacity to approximately 67% capacity.
A single speed, high efficiency motor continues to run while the scroll
modulates between the two capacity steps. Modulation is achieved by
venting a portion of the gas in the first suction pocket back to the low
side of the compressor, thereby reducing the effective displacement of
the compressor.
Full capacity is achieved by blocking these vents, thus increasing the
displacement to 100%. A DC solenoid in the compressor controlled by a
rectified 24 volt AC signal in the external solenoid plug moves the slider
ring that covers and uncovers these vents.
The vent covers are arranged in such a manner that the compressor
operates at approximately 67% capacity when the solenoid is not
energized and 100% capacity when the solenoid is energized. The
loading and unloading of the two step scroll is done ”on the fly” without
shutting off the motor between steps.
NOTE:
67% compressor capacity translates to approximately 75%
cooling or heating capacity at the indoor coil.
The compressor will always start unloaded and stay unloaded for five
seconds even when the thermostat is calling for high stage capacity.
Quiet Shift-2
Quiet shift- 2 is a field selectable defrost mode (factory set to OFF),
which will reduce the occasional noise that could be heard at the start of
defrost cycle and restarting of heating cycle. It is selected by placing DIP
switch 3 on defrost board in the ON position. When Quiet Shift- 2
switch is placed in ON position, and defrost is initiated, the following
sequence of operation will occur: The compressor will be de- energized
for approximately 1 minute, then the reversing valve will be energized.
A few seconds later, the compressor will be re- energized and the normal
defrost cycle starts.
Once defrost termination conditions have been met, the following
sequence will occur: The compressor will be de- energized for
approximately 1 minute, then the reversing valve will be de- energized.
A few seconds later, the compressor will be re- energized and the normal
heating cycle starts.
CAUTION
!
PERSONAL INJURY HAZARD
Failure to follow this caution may result in personal
injury.
Wear safety glasses, protective clothing, and gloves when handling
refrigerant and observe the following:
• Front seating service valves are equipped with Schrader valves.
CAUTION
!
ENVIRONMENTAL HAZARD
Failure to follow this caution may result in environmental damage.
Federal regulations require that you do not vent refrigerant to the
atmosphere. Recover during system repair or final unit disposal.
CAUTION
!
UNIT OPERATION AND SAFETY HAZARD
Failure to follow this caution may result in personal injury, equipment
damage or improper operation.
• Do not overcharge system with refrigerant.
• Do not operate unit in a vacuum or at negative pressure.
• Do not disable low pressure switch in scroll compressor applications.
• Compressor dome temperatures may be hot.
