Service manual

Classic HVPA & HVPSA M&S 8.09-1 15700 - 11 HVAC Equipment
it removes foreign particulate matter, e.g. dirt, scale, solder particles from the
refrigerant to protect the compressor and other components in the refrigerant system
with small openings or close tolerances. Second, it absorbs any moisture in the
refrigerant with desiccant granules.
F. High Pressure Switch and Loss of Charge Switch. These switches render the
compressor and outdoor fan motor inoperative whenever the limits of the high or
loss of charge switches are exceeded. In the event of high pressure, the Classic
TM
unit will turn off and lockout. The high pressure switch opens at 610 psig and resets
at 420 psig.
The Loss of Charge Switch is designed to guard against the operation of the system
in the event of a loss of refrigerant. The loss of charge switch opens at 40 psig and
closes at 60 psig.
In cold weather the pressure in the refrigerant system is low prior to operation. When
the Classic™ unit starts in the heat pump mode during cold weather, low pressure
could cause the system to lock out. To guard against nuisance lockouts, the Classic
unit will not shut off if the Loss of Charge Switch (LPS) comes on during the first
eight minutes of operation. In other words, the compressor will start and operate for
eight minutes even with the LPS switch off.
The high and low pressure switches are resettable at the wall thermostat or by
turning power off and then on to the Classic
TM
unit.
G. Metering Devices. The Classic uses a thermal expansion valve on the indoor
(cooling) circuit and a fixed orifice on the outdoor (heating) circuit.
H. Reversing Valve. The reversing valve reverses the refrigerant’s direction of flow in a heat
pump, allowing the heat pump to switch from cooling to heating or heating to cooling.
I. Exhaust Air Ventilation Blower is used to exhaust classroom in the GreenWheel
ERV ventilation option. The blower can exhaust up to 450 CFM of air from the
classroom. In the standard configuration, both the exhaust and the intake ventilation
blowers are controlled by a single speed controller. This speed controller permits
the motor speed to be adjusted for the correct cfm of ventilation air. As an option,
a second motor controller may be factory installed to allow independent control of
the intake and exhaust air blowers. This allows pressurization of the classroom. All
ventilation options have an intake air blower.
J. Intake Ventilation Air Blower (GreenWheel ERV only) is used to introduce
outside air into the classroom.
K. Electric Resistance Heat. The heaters are available in various sizes (kW) for
operation on 208/230v. 1Ø, 208/230 v. 3Ø, and 460v, 3Ø. The model number of the
heat pump indicates the power supply and kW.
L. Electric Resistance Heat Controls. Included with the electric heat assembly are
temperature switches designed to turn power off to the heaters if the temperature
is too high. There are two types of temperature switches. The first is an auto-reset
type that turns power off to the heater if it senses a temperature of 145°F. When
the temperature drops to approximately 105°F, power is restored to the heaters. This
auto-reset switch is in the low voltage circuit.