11
Made in Rome, New York, USA
VPAC/VPHP
!
!
HEAT PUMP COOLING OPERATION
(VPHP ONLY)
Cooling operation in a heat pump unit is described in
“Cooling Operation” above. The unit is equipped with a re-
versing valve that is energized for cooling and de-energized
in heating mode.
HEAT PUMP HEATING OPERATION
(VPHP ONLY)
Heat pump units are “Limited Range” equipped with
back-up electric resistance heat. Limited range heat pumps
are designed to operate when outdoor temperatures are
between 75°F and 40°F and with a maximum indoor tem-
perature of 80°F. When the outdoor temperature falls below
approximately 40°F the unit will switch from heat pump to
electric resistance heat. Electric heat will then remain as the
heat source until the outdoor temperatures rise above 50°F.
The VPHP is a single-stage heating unit. The electric heat
and heat pump will not operate simultaneously.
To operate the unit in heating mode, it must first be
connected to an appropriate heat pump thermostat. (See
“choosing a thermostat”). Select heat on the thermostat
system switch. Then, adjust the set-point temperature above
the room temperature. The compressor and fan motors
will start and heating will begin. If the outdoor temperature
is below approximately 40°F the heat pump system will
not operate. Electric heat will then take over the heating
demand. Heating will continue so long as the set-point
temperature remains above the room temperature. Place
the set-point temperature below the room temperature. The
heating mode will cease and the indoor fan will remain on
for an additional sixty seconds.
IMPORTANT:
The start of the compressor will not take
place until the anti-short/random start time period has
elapsed.
EMERGENCY HEAT
(VPHP ONLY)
WARNING
Before accessing the control compartment, disconnect
power to the unit. Failure to do so could result in serious
injury or electrical shock.
Should the heat pump system fail, it is possible to force
the control board into electric heat mode. This is a tempo-
rary solution until the heat pump system can be repaired.
Locate the circuit board in the control section of the unit.
Locate the terminals where the outdoor sensor connects
to the circuit board. Using a small needle nose type pliers,
disconnect one side of the sensor from the circuit board.
This will appear to the circuit board as an outdoor coil freeze
condition, thereby energizing the electric resistance heater
on the call for heat.
THERMOSTATIC DRAIN PAN VALVE
(VPHP ONLY)
Heat pump units are equipped with a thermostatic
drain valve that will open when outdoor temperatures fall
below 50°F. This keeps the base pan free of condensate
water where it may otherwise freeze during colder outdoor
temperatures. As part of its normal operation, the unit will
produce condensate and collect it in the base pan of the unit.
There it will be picked up by the condenser fan slinger ring
and deposited onto the condenser coil. During the cooling
season, this improves the unit’s efficiency by maintaining
adequate refrigeration system pressures.
CHANGEOVER THERMOSTAT
(VPHP Only)
This feature has been replaced by a circuit board how-
ever is still used on some units. The changeover thermostat
monitors outdoor temperature for efficient heat pump opera-
tion. In heating, the thermostat will determine weather to
use heat pump or electric resistance heat. When outdoor
temperatures fall below approximately 35°F, the changeover
thermostat (COT) will switch from heat pump operation to
electric resistance heat. Electric heat will remain the primary
heat source until outdoor temperature rises above 50°F. The
COT is factory pre-set and should never need adjusting. If
the adjustment screw is tampered with it will be necessary
to reset the freeze-stat. To set the freeze stat you will need
a medium flat bladed screwdriver. Turn the adjusting screw
counter-clockwise until it stops. Then slowly turn the adjust-
ing screw clockwise approximately 1/8 turn until a click is
detected. The freeze stat is now set.
ANTI-SHORT CYCLE TIMER RANDOM START
This feature will prevent compressor short cycling and
also prevent multiple units in a single facility from simultane-
ously starting following a power outage. This delay on break
feature ensures that the compressor remains off between
cycles until the three-minute time delay period has elapsed,
allowing system pressures to equalize before restarting.
The random start feature, initiated after a power failure,
will add a random time delay (between 5-120 seconds) to
the three-minute anti short cycle time following a power
outage. This will stagger the starting of multiple units in a
single facility allowing a building to slowly go back on line
when power is restored.
INDOOR COIL FREEZE PROTECTION
This feature will prevent the indoor coil from freeze up in
the cooling mode. Indoor coil freeze up can occur due to a
dirty air filter, low refrigerant charge or low room or outdoor
temperatures. This in turn can cause compressor damage.
Should a freeze condition be detected, the compressor and
condenser fan will be switched off for a minimum of three
minutes and until the freeze condition is satisfied. During
this time the indoor fan will continue to run to aid in the
defrost process.
SEQUENCE OF OPERATION
Summary of Contents for VPAC
Page 16: ......
