Airxcel Marvair Classic HVPA24HP Manual

MAINTENANCE &
SERVICE
Classic HVPA & HVPSA M&S 8.09-1
Models
HVPA24-30-36-42-49-60 &
HVPSA36-42-49-60
CAUTION!!
Read all instructions before use.
Retain this manual for future
reference. This equipment should
be installed and serviced only by a
trained professional HVAC service
person.
Due to continuous product
improvement, use only the current
issue of this manual. The latest
version can be downloaded from the
Marvair website - www.marvair.com.
Classic HVPA & HVPSA
Heat Pumps
Manufactured By:
Marvair®Division of AIRXCEL®, Inc.
P.O. Box 400 • Cordele, Georgia 31010
156 Seedling Drive • Cordele, Georgia 31015
[phone] • Fax [phone]
E-mail: [email protected] • Internet: www.marvair.com

Classic HVPA & HVPSA M&S 8.09-1 15700 - 2 HVAC Equipment
SECTION 15700
HEATING, VENTILATING AND AIR CONDITIONING EQUIPMENT
MAINTENANCE & SERVICE MANUAL
FOR CLASSICTM HEAT PUMP
TABLE OF CONTENTS
Chapter Description Page
1.1 General Description ..................................................................3
1.2 Model Identification ..................................................................4
2.1 Start-up Instructions.................................................................5
2.2 Ventilation System Calibration....................................................7
3.1 Electrical..................................................................................9
4.1 Maintenance ............................................................................9
5.1 Function & Description of Primary Components.........................10
6.1 Troubleshooting......................................................................13
7.1 Filing a Service/Warranty Claim ...............................................23
8.1 Warranty Statement................................................................24
9.1 Parts List................................................................................25

Classic HVPA & HVPSA M&S 8.09-1 15700 - 3 HVAC Equipment
SECTION 15700
HEATING, VENTILATING AND AIR CONDITIONING EQUIPMENT
The purpose of this manual is to provide instructions for maintenance and service for the
Marvair®Classic™ series of heat pumps. In addition to this manual, there are other pieces of
literature available from Marvair. The Product Manual covers the installation of the unit and
various accessories and the initial start-up of the unit. An overview of the product line can be
found in the Classic Product Data Sheets. The current version of this literature can be found
and downloaded from the Marvair website at www.marvair.com.
To minimize sound levels within the classroom, certain options should be selected. These op-
tions are designated by throughout the guideline.
1.1 GENERAL OPERATION
A. Classic™ heat pumps are designed to provide quiet comfort to the classroom.
In cooling mode, the compressor will cycle on to provide the cooling required. The
system provides cooling, dehumidification and air circulation.
In heating mode the compressor (heat pump only) will cycle on to provide the
heating required. The system provides heating and air circulation. At lower outdoor
temperatures, additional heating capacity may be provided by an optional electric
resistance heater.
Ventilation air may be provided by the manual or motorized fresh air vent, power
vent or GreenWheel®ERV. These ventilation systems operate when there is a call
for cooling or heating or independently to provide fresh air. Note that with the
manual, motorized fresh air vent and the power vent options, if the compressor is
not operating and the indoor blower is running, unconditioned outside air is being
introduced into the classroom. The GreenWheel ERV provides tempered outside air.
Control systems are either a remote external thermostat, internal thermostat, or a
direct digital control interfacing with the building automation system (BAS).
Hot Gas Reheat (HGR) Dehumidification (Option). To provide on demand
dehumidification, the Classic™ heat pump can have a factory installed hot gas reheat
coil to allow dehumidification through continued cooling with discharge air reheated
to avoid over cooling the classroom. The operation of the HGR is controlled by a
three-way heat reclaim valve. The HGR coil is sized to provide a heating capacity
approximately equal to the sensible capacity of the unit When the demand for
cooling is satisfied and the humidity controller calls for dehumidification, hot gas is
directed to a reheat coil downstream from the evaporator coil to add heat to the
dehumidified, chilled air supplied to the classroom. Hot gas reheat is available with
motorized fresh air, PowerVent and GreenWheel®ventilation systems.
Marvair®recommends that for optimum performance, hot gas reheat be used in
conjunction with the GreenWheel®heat recovery ventilator. When used with other
ventilation options, hot gas reheat may not maintain satisfactory control of the
humidity in the classroom over all outdoor conditions.

Classic HVPA & HVPSA M&S 8.09-1 15700 - 4 HVAC Equipment
1.2 MODEL IDENTIFICATION
The ClassicTM heat pump identification numbering system is shown below. The model
identification number is on the data label. The data label is at the bottom of the of left
side panel.
IMPORTANT
WHEN CLASSIC SYSTEMS ARE INSTALLED, MODEL NUMBER AND SERIAL
NUMBERS ARE TO BE RECORDED AND MAINTAINED IN A LOCATION FOR
IMMEDIATE ACCESS WHEN REQUESTING FURTHER INFORMATION.

Classic HVPA & HVPSA M&S 8.09-1 15700 - 5 HVAC Equipment
2.1 START-UP PROCEDURE
Important: If your unit has a crankcase heater be sure that the crankcase heater has been
energized for at least 24 hours prior to start-up of the unit. Double check all electrical con-
nections before applying power. Various thermostats can be used to control the heat pump.
The thermostat may have a fan switch with an Automatic and On positions, a system switch
with Heat, Cool, and Off positions, and an emergency heat position with lights. The spec
sheets have detailed description of the various Marvair®thermostats. Since other thermo-
stats or remote control systems may be used, the following procedures should be viewed as
guidelines for standard thermostats with system and fan switches.
Check-out of Cooling Cycle
Procedure:
Classic™ Heat Pump
1. Set the fan switch to "Auto" and the system switch to "Off".
2. Move the cooling temperature on the wall thermostat to a point higher than the
room temperature. Move the heating temperature to a temperature that is lower
than the room temperature.
3. Set the thermostats system switch to "Cool" or "Auto" position. Nothing should
operate at this time.
4. Set the time delay in the control box to three minutes. Note that time delay is an
option on some Classic™ units and may not be on your heat pump.
5. Remove the cover plate from the thermostat. Slowly lower the thermostat cooling
temperature. Once the indoor fan turns on, allow approximately three minutes for
the compressor and outdoor fan to start.
For units equipped with the low ambient control, note that the outdoor fan may not
come on immediately, because it is cycled by refrigerant pressures. Some units have
a time delay module which prevents the compressor from restarting immediately
after interruption of power. See section 1.5P and 1.5Q for details on the operation of
the low ambient control and the time delay.
If the unit fails to operate, refer to the troubleshooting information in Chapter 6.1.
Classic™ Heat Pump with Economizer
1. Set the fan switch to "Auto" and the system switch to "Off".
2. Set the cooling temperature on the wall thermostat to a point higher than the room
temperature. Set the heating temperature to a temperature that is lower than room
temperature.
3. Set the thermostat system switch in the "Auto" or "Cool" position. Nothing should
operate at this time.

Classic HVPA & HVPSA M&S 8.09-1 15700 - 6 HVAC Equipment
4. Set the time delay in the Classic™ Heat Pump with Economizer control box to
3 minutes. Check the enthalpy changeover setting of the H205A or dry bulb sensor,
and reset it if needed. Refer to the Owner’s manual for instructions on setting the
H205A or dry bulb sensor.
5. Slowly lower the thermostat’s cooling temperature. The indoor fan should operate.
Once the indoor fan comes on, allow approximately three minutes for the compressor
to start. Note that the outdoor fan may not come on immediately because it is
cycled by refrigerant pressures
Note: To check the system operation under different ambient conditions, the air
temperature and enthalpy sensors must be "tricked". When outdoor ambient
conditions are higher than the control setting, a component aerosol cooler may be
sprayed directly into the enthalpy sensor to simulate low enthalpy conditions, causing
the economizer damper to open.
Alternately, when outdoor conditions are lower than the set point, a source of heat
such as a hair dryer can be directed on the air temperature sensor to simulate warmer
conditions, which will bring on mechanical cooling and start the compressor.
If the unit fails to operate, refer to the troubleshooting information in Chapter 6.1.
Check-Out of Heating Cycle
Procedure:
1. Place the thermostat system switch to "Auto" or "Heat" and the fan to "Auto".
2. Raise the heating temperature to a setting which is higher than the room
temperature. The fan and compressor should cycle on after time delay (standard on
Classic™ heat pump with economizer and all HVP models, option on all other Classic
units) has cycled.
3. Move the system switch to the "Off" position. All functions should stop.
The Blower Timed Delay Relay (BTR) keeps the blower running for 90 seconds after
the unit shuts off.
Note: The damper blade should remain closed during the heating cycle (unless the
minimum position potentiometer has been set for constant ventilation).

Classic HVPA & HVPSA M&S 8.09-1 15700 - 7 HVAC Equipment
2.2 VENTILATION SYSTEM CALIBRATION
Manual Fresh Air System (Configuration N). This is the standard ventilation
system in the Classic™ heat pump. Fresh air ventilation by means of a damper can
provide up to 15% of rated air flow of outside air. The damper has four positions
corresponding to 0, 5, 10 and 15% of rated air flow of outside air.
The damper only opens when the indoor fan is operating. Position the screw on the
side of the damper hood for the desired air flow.
Manual Damper - 0 to 450 cfm of Outside Air, No Pressure Relief
(Configuration Y). The amount of fresh air is determined by the position of the
collar on the rod. To determine the desired quantity of fresh air:
a. With the indoor blower on, measure the quantity of supply air being discharged
into the room with a balometer.
b. Now measure the quantity of the return air from the room. Subtract the return
air from the supply air. The difference is the amount of fresh air.
c. Loosen the set screw that holds the collar onto the rod connected to the damper.
Move the collar and tighten the set screw.
Figure 1. Damper Adjustment
d. Repeat steps a, b and c until the desired amount of fresh air is being introduced
into the room.
Important Note: Since Configuration Y does not have internal pressure relief,
the fresh air must have a passage to the outside. If a passage is not available, the
desired quantity of fresh air cannot be introduced into the room.
Motorized Damper - 0 to 450 cfm of Outside Air and Pressure Relief
(Configuration B) and the Manual Damper with Pressure Relief
(Configuration Z). The settings of the damper require a balometer and a
thermometer for measuring internal and external temperatures.
a. Measure the total supply air with a balometer. If the supply air is controlled by
a manual fan speed controller, make certain that the air flow is in accordance
Rod
Set Screw

Classic HVPA & HVPSA M&S 8.09-1 15700 - 8 HVAC Equipment
with the air flow ((CFM) at various static pressures chart. This chart can be found
in the Classic Product Data Sheet or the Installation Manual. This CFM is referred to
as "C" in the illustration and equation below.
Figure 2. Damper Air Path
b. "A" is the quantity of outside air expressed as a percentage of "C". For example,
if the supply air is 1,220 CFM and 300 CFM of outside air is required, "A" is 25%
(300 CFM/1,220 CFM).
Measure the temperature of the outside air.
Multiply the temperature by "A".
c. "B" is the quantity of return air expressed as a percentage of "C". "A" and "B"
must equal 100%.
Measure the temperature of the indoor return air.
Multiply the temperature of the indoor air by "B".
d. Calculate what the Tmix should be with the desired quantity of outside air.
Measure the actual temperature of Tmix at the inlet to the supply air blower or at
the inlet of the supply air blower.
Adjust the damper blade until the measured value of the Tmix equals the
calculated or desired value of Tmix.
The motorized damper, Configuration B, can be controlled by an optional relay
that allows additional external control with a choice of 24, 120 or 240V coils to
regulate fresh air ventilation in response to a control located remote from the
Classic™ heat pump.
9. Electrical Supply:
The power supply must have the appropriate voltage, phase, and ampacity for the

Classic HVPA & HVPSA M&S 8.09-1 15700 - 9 HVAC Equipment
3.1 ELECTRICAL
Classic heat pumps and air conditioners are built in a wide variety of configurations and op-
tions. The illustrations of the control center and the electrical schematics shown here are typical,
but probably are not identical to your units. Please refer to the electrical schematic in each unit
for the specific construction of that unit.
model selected. Voltage must be maintained above minimum specified values listed
below. Refer to the unit data plate for ampacity requirements.
Table 1. Voltage Limitations
Electrical Rating Designations* A C D
Nominal Voltage 208/230 208/230 460
Phase 1 3 3
Minimum Voltage 197 197 414
Maximum Voltage 253 253 506
* Letters refer to model number code designations.
4.1 MAINTENANCE
Marvair®strongly recommends that the heat pump be serviced a minimum of twice a
year – once prior to the heating season and once prior to the cooling season. At this
time the filters, evaporator coil, condenser coil, the cabinet, and condensate drains
should be serviced as described below. Also at this time, the heat pump should be
operated in the cooling and heating cycles as described in Chapter 3, Start-Up. In
addition to this seasonal check-out, the unit should be maintained as follows:
Air Filter
Replace the air filter whenever it is visibly dirty.
Indoor Coil
If the coil becomes clogged or dirty, it may be cleaned by careful vacuuming or with
a commercial evaporator cleaning spray. DO NOT use a solvent containing bleach,
acetone, or flammable substances. Turn power OFF before cleaning. Be careful
not to wet any of the electrical components. Be sure the unit has dried before
restarting.
Outdoor Coil
Periodically inspect the outdoor coil and the cabinet air reliefs for dirt or obstructions.
Remove foreign objects such as leaves, paper, etc.
If the coil is dirty, it may be washed off with a commercial solvent intended for
this purpose. TURN OFF POWER BEFORE CLEANING! Be sure that all electrical
components are thoroughly dry before restoring power.
Cabinet
The cabinet may be cleaned with a sponge and warm, soapy water or a mild
detergent. Do not use bleach, abrasive chemicals or harmful solvents.

Classic HVPA & HVPSA M&S 8.09-1 15700 - 10 HVAC Equipment
Drains
Regularly check the primary and secondary condensate drains. The secondary drain
has a stand pipe. An obstruction will force water to dump into the middle of the
unit and drain out the sides of the Classic™ Heat Pump, causing discoloration of the
side panels. If discoloration is noted, service the drains.
If a commercial drain solvent is used, flush out the drain pan and system with plenty
of fresh water to prevent corrosion.
Lubrication
Oiling of the condenser fan motor or the evaporator blower motor is not
recommended.
5.1 FUNCTION AND DESCRIPTION OF PRIMARY COMPONENTS
A. Compressor. All Classic units use a fully hermetic scroll compressor to minimize
sound levels and maximize efficiency. Scroll compressors, like several other types
of compressors, will only compress in one rotational direction. The direction of
rotation is not an issue with single-phase compressors since they will always start
and run in the proper direction. However, three phase compressors will rotate in
either direction depending upon phasing of power. Since there is a 50-50 chance
of connecting power in such a way as to cause rotation in the reverse direction, it
is imperative to confirm that the compressor is rotating in the proper direction at
the initial field start-up of the system. Verification of proper rotation is made by
observing that the suction pressure drops and the discharge pressure rises when
the compressor is energized. An alternate method of verification for self contained
system with small critical refrigerant charges, where the installation of gauges may
be objectionable, can be made by monitoring the temperature of the refrigerant
lines at the compressor. The temperature should rise on the discharge line while the
suction line temperature decreases. Reverse rotation also results in a substantially
reduced current draw when compared to tabulated values.
There is no negative impact on durability caused by operating three phase
compressors in the reversed direction for a short duration of time, usually defined
as less than one hour. However, after several minutes of operation the compressor's
internal protector will trip. The compressor will then cycle on the protector until
the phasing is corrected. Reverse operation for longer than one hour may have a
negative impact on the bearings.
B. Indoor Blower and Motor. The indoor blower assembly is an electronically
commutated blower motor and dual blowers.
C. Outdoor Air Mover. The outdoor air mover is an axial fan with an asynchronous
external rotor motor.
D. Indoor/Outdoor Coils. The coils are constructed of lanced, aluminum fins
mechanically bonded to rifled, seamless copper tubes.
E. Filter Drier - The filter drier performs two functions in the refrigerant circuit. First,

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 ClassicTM
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 ClassicTM 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.

Classic HVPA & HVPSA M&S 8.09-1 15700 - 12 HVAC Equipment
The second type of switch is a one time limit switch. If it senses a temperature of
300ºF, power is turned off to the elements. This switch does NOT reset when the
temperature drops and must be replaced when it activates.
The number and location of both switches is determined by the power supply and the
kW of the heaters.
M. Ventilation Blower Fan Speed Control. Factory setting for the indoor blower
speed is full speed. If a lower speed setting is required, the blower motor speed
control may be adjusted with a slotted screwdriver rotating the speed control as
shown in Figure 3. Reference unit label for minimum required air flow settings for
specific unit model.
Figure 3. Ventilation Blower Speed Control Adjustment Instructions
N. Standard Ventilation Control. The GreenWheel®ERV ventilation option is
equipped with a fresh air fan speed control. The fresh air fan speed control
operates both the ventilation intake and exhaust blowers together.
The GreenWheel®ERV ventilation option can be equipped with an exhaust fan air
speed control, which controls the ventilation exhaust blower independently of the
fresh air intake blower.
Demand Control Ventilation. A field or factory installed carbon dioxide sensor
controls the ventilation damper and only opens the damper when CO2 levels exceed
a specified level. Demand control ventilation saves energy and utility costs by
ventilating the classroom based upon occupancy.
Note: Not available on manual fresh air damper (“B”) configuration.
O. Outdoor Thermostat. Factory set at 40°F, this thermostat determines the outdoor
temperature at which the supplemental electric heat turns on. This may be field
adjusted to the desired temperature setting by rotating the adjustment knob.
P. Low Ambient Control (Standard on units with economizers, optional on all other
units.) The low ambient control permits mechanical cooling when outdoor ambient
temperatures are low. The control uses a reverse-acting high pressure switch to cycle
the condenser fan motor according to liquid refrigerant pressure conditions. Switch
closure and fan operation occurs when the pressure reaches 400 PSIG. The switch
opens again when the refrigerant pressure falls to 245 PSIG. Therefore, the outdoor
SERIES 706
VARI-SPEED
MOTOR CONTROL
LO HI

Classic HVPA & HVPSA M&S 8.09-1 15700 - 13 HVAC Equipment
6.1 TROUBLESHOOTING
In diagnosing common faults in the heat pump system, develop a logical thought
pattern as used by experienced technicians. The charts which follow are not intended
to be an answer to all problems but only to guide the technician’s thinking. Through
a series of yes and no answers, follow the logical path to a likely conclusion.
A novice technician should use these charts like a road map. Remember that the
chart should clarify a logical path to the problem’s solutions.
Electrical Checks Flow Chart
Unit Running?
NO YES
Thermostat Problem?
Go to Mechanical Check
for Cooling or Heating
YES - Repair and Recheck NO
Transformer Problem?
YES - Repair and Recheck NO
Voltage on Compressor Side of Contactor?
YES NO
Run Capacitor Voltage on Line Side of Contactor?
Compressor Internal
Overload Open
NO YES
Compressor Winding
Open
Circuit Breakers or
Fuses Open Compressor Contactor
Unit Wiring and
Connections YES High Pressure Cut-Out
Compressor Winding
Grounded
Low Pressure Cut-Out
Outdoor Fan Motor
Grounded
Compressor Time
Delay
Grounded Capacitor Unit Wiring and
Connections
Replace Fuses or
Reset Breakers and
Recheck System
fan always starts after the compressor, and it will cycle frequently during normal
operation at low outdoor conditions.
Q. Compressor Time Delay. The time delay module (delay on make) prevents the
compressor from restarting immediately after interruption of power. The delay
interval, which is adjustable from .2 to 8 minutes, protects the compressor by
allowing internal refrigerant pressures to equalize. The time delay does not effect the
electric heat circuit.

Classic HVPA & HVPSA M&S 8.09-1 15700 - 14 HVAC Equipment
Cooling Mechanical Checks Flow Chart
Unit Running?
YES NO
Pressure Problems?
Go to Electrical
Checks Flow Chart
High Head
Pressure
Low Head
Pressure
Low Suction
Pressure
Dirty Outdoor Filter Low on Charge Dirty Filters
Inoperative Outdoor
Fan
Low Ambient
Temperature
Dirty Indoor Coil
Overcharge Inoperative
Compressor Valves
Inadequate Indoor Air
Flow
Recirculation of
Outdoor Air
Outdoor Check Valve
Closed
Inoperative Indoor
Blower
Non-condensibles Restricted Indoor
Metering Device
Low on Charge
Higher than Ambient
Air Entering Outdoor
Coil
Restricted Filter
Drier
Restricted Indoor
Metering Device
Wrong Outdoor Fan
Rotation
Reversing Valve
Failure
Restriction in System
Recirculation of
Indoor Air
Wrong Indoor
Blower Rotation
Inadequate Ducts
Outdoor Check
Valve Closed
Restricted Filter Drier

Classic HVPA & HVPSA M&S 8.09-1 15700 - 15 HVAC Equipment
Heating Mechanical Checks Flow Chart
Unit Running?
YES NO
Pressure Problems?
Go to Electrical
Checks Flow Chart
High Head
Pressure
Low Head
Pressure
Low Suction
Pressure
Dirty Filters Low on Charge Dirty Outdoor Coil
Dirty Indoor Coil Low Indoor
Temperature
Inadequate Air Flow
Over Outdoor Coil
Inoperative Indoor
Blower
Closed Indoor Check
Valve
Inoperative OD Fan
Overcharge Inoperative
Compressor Valves
Low on Charge
Inadequate Indoor Air
Flow
Restricted Outdoor
Metering Device
Restricted Outdoor
Metering Device
Non-condensibles Restricted Filter Drier Restriction in System
Wrong Indoor Blower
Rotation
Reversing Valve Failure Closed Indoor Check
Valve
Inadequate Ducts Recirculation of Out-
door Air
Restricted Filter Drier
Defrost Mechanical Checks Flow Chart
Defrost System
No Defrost Incomplete Defrost Excessive Defrost
Reversing Valve Stuck Poor Sensor Location Wrong Defrost Control
Timer Setting
No Defrost Timer
Control Power
Wrong Defrost Control Timer
Setting
Poor Sensor Location
Failed Defrost Control Failed Defrost Relay (doesn’t
stop O.D. Fan)
Low System Charge
Failed Defrost Relay Thermostat Satisfies During
Defrost
Wind Affecting in Defrost
Loose Default Sensor

Classic HVPA & HVPSA M&S 8.09-1 15700 - 16 HVAC Equipment
Subcooling Calculation
1. Measure the liquid pressure at the liquid line service valve.
2. Convert the liquid line pressure to saturated temperature. See tables below.
3. Measure the liquid line temperature at the liquid line service valve.
4. Compare the liquid line temperature to the saturated temperature.
5. The difference between saturated temperature and liquid line temperature is the
subcooling. Subcooling normal range 12° to 20°.
Superheat Calculation
1. Measure the suction pressure at the suction line service valve.
2. Convert the suction line pressure to saturated temperature. See tables below.
3. Measure the suction line temperature approximately 6” to 8” from the compressor.
4. Compare the suction line temperature to the saturated temperature.
5. The difference between saturated temperature and suction line temperature is the
superheat. Superheat normal range 12° to 18°
Temperature Pressure Chart
Temp.
(°F)
R-22
PSIG
R-410A
PSIG
Temp.
(°F)
R-22
PSIG
R-410A
PSIG
Temp.
(°F)
R-22
PSIG
R-410A
PSIG
-40 0.5 11.0 25 48.7 86.0 90 168.4 273.0
-35 2.6 14.2 30 54.9 95.5 95 181.8 294.1
-30 4.9 17.8 35 61.5 105.7 100 195.9 316.4
-25 7.4 21.8 40 68.5 116.6 105 210.7 339.9
-20 10.1 26.1 45 76.0 128.3 110 226.3 364.6
-15 13.2 30.8 50 84.0 140.8 115 242.7 390.5
-10 16.5 35.9 55 92.5 154.1 120 259.9 417.7
-5 20.0 41.5 60 101.6 168.2 125 277.9 446.3
0 23.9 47.5 65 111.2 183.2 130 296.8 476.3
5 28.2 54.1 70 121.4 199.2 135 316.5 507.6
10 32.8 61.2 75 132.2 216.1 140 337.2 540.5
15 37.7 68.8 80 143.6 234.0 145 258.8 574.8
20 43.0 77.1 85 155.7 253.0 150 381.5 610.6

Classic HVPA & HVPSA M&S 8.09-1 15700 - 17 HVAC Equipment
Troubleshooting Chart
WARNING
DISCONNECT ALL POWER TO UNIT BEFORE SERVICING. CONTACTOR
MAY BREAK ONLY ONE SIDE. FAILURE TO SHUT OFF POWER CAN
CAUSE ELECTRICAL SHOCK RESULTING IN PERSONAL INJURY OR DEATH.
Problem/Symptom Likely Cause(s) Correction
Unit will not run. Power off or loose electrical
connection.
Thermostat out of calibration
- set too high.
Defective contactor.
Blown fuse/tripped breaker.
Transformer defective.
High pressure control open.
Low pressure control open.
1.
2.
3.
4.
5.
6.
7.
Check for correct voltage at unit discon-
nect. Check for correct voltage at contac-
tor in unit.
Reset.
Check for 24 volts at contactor coil -
replace if contacts are open.
Replace fuses/reset breaker.
Check wiring - replace transformer.
Reset.
Reset.
1.
2.
3.
4.
5.
6.
7.
Outdoor fan runs,
compressor doesn’t.
Run capacitor defective
Loose connection.
Compressor stuck, grounded
or open motor winding, open
internal overload.
Low voltage condition.
1.
2.
3.
4.
Replace.
Check for correct voltage at compressor
- check and tighten all connections.
Wait at least 2 hours for overload to
reset. If still open, replace the
compressor.
Add start kit components.
1.
2.
3.
4.
Insufficient cooling. Improperly sized unit.
Improper indoor air flow.
Incorrect refrigerant charge.
Air, non-condensibles or mois-
ture in system.
1.
2.
3.
4.
Recalculate load.
Check - should be approximately 400 CFM
per ton.
Charge per procedure.
Recover refrigerant, evacuate and
recharge, add filter drier.
1.
2.
3.
4.
Compressor short cycles. Incorrect voltage.
Defective overload protector.
Refrigerant undercharging.
1.
2.
3.
At compressor terminals, voltage must be
±10% of nameplate marking when unit is
operating.
Replace - check for correct voltage.
Add refrigerant.
1.
2.
3.
Registers sweat. Low indoor air flow.1. Increase speed of blower or reduce
restriction - replace air filter.
1.
High head - low vapor
pressures.
Restriction in liquid line, expan-
sion device or filter drier.
Flow check piston size too small.
Incorrect capillary tubes.
1.
2.
3.
Remove or replace defective
component.
Change to correct size piston.
Change assembly coil.
1.
2.
3.
High head - high or
normal vapor
pressures - cooling
mode.
Dirty outdoor coil.
Refrigerant overcharge.
Outdoor fan not running.
Air or non-condensibles in
system.
1.
2.
3.
4.
Clean coil.
Correct system charge.
Repair or replace.
Recover refrigerant, evacuate and
recharge.
1.
2.
3.
4.

Classic HVPA & HVPSA M&S 8.09-1 15700 - 18 HVAC Equipment
Problem/Symptom Likely Cause(s) Correction
Low head - high vapor
pressures.
Flow check piston size too large.
Defective compressor valves.
Incorrect capillary tubes.
1.
2.
3.
Change to correct size piston.
Replace compressor.
Replace coil assembly.
1.
2.
Low vapor - cool com-
pressor - iced indoor coil.
Low indoor air flow.
Operating below 55°F outdoors.
Moisture in system.
1.
2.
3.
Increase speed of blower or reduce
restriction - replace air filter.
Add low ambient kit.
Recover refrigerant - evacuate and
recharge - add filter drier.
1.
2.
3.
High vapor pressure. Excessive load.
Defective compressor.
1.
2.
Recheck load calculation.
Replace.
1.
2.
Fluctuating head and
vapor pressures..
TXV hunting.
Air or non-condensibles in sys-
tem.
1.
2.
Check TXV bulb clamp - check air distribu-
tion on coil - replace TXV.
Recover refrigerant, evacuate and
recharge.
1.
2.
Gurgle or pulsing noise
at expansion device or
liquid line.
Air or non-condensibles in sys-
tem.
1. Recover refrigerant, evacuate and
recharge.
1.
Service Analyzer Charts
Compressor Overheating
Problem/Symptom Likely Cause(s) Correction
High superheat. Low charge.
Faulty metering device.
High internal load.
Restriction in liquid line.
Low head pressure.
1.
2.
3.
4.
5.
Check system charge.
Restricted cap tube, TXV.
Power element superheat adjustment.
Foreign matter stopping flow.
Hot air (attic) entering room.
Heat source on; miswired or faulty
control.
Drier plugged.
Line kinked.
Low charge.
Operating in low ambient temperatures.
1.
2.
3.
4.
5.
Low voltage. Loose wire connections.
Dirty or pitted compressor
contactor contacts.
Power company problem, trans-
former.
Undersized wire feeding unit.
1.
2.
3.
4.
Check wiring.
Replace contactor.
Have problem corrected before diagnosis
continues.
Correct and complete diagnosis.
1.
2.
3.
4.
High voltage. Power company problem.1. Have problem corrected.1.
Troubleshooting Chart (cont’d)

Classic HVPA & HVPSA M&S 8.09-1 15700 - 19 HVAC Equipment
Compressor Overheating (cont’d)
Problem/Symptom Likely Cause(s) Correction
High head pressure. Overcharge.
Dirty heat pump coil.
Faulty or wrong size heat pump
fan motor.
Faulty outdoor blower.
Recirculation of air.
Additional heat source.
Non-condensibles
1.
2.
3.
4.
5.
6.
7.
Check system charge.
Clean coil.
Replace fan motor.
Replace blower.
Replace with correct rotation motor.
Correct installation.
Check for recirculating from other equip-
ment.
Recover refrigerant, evacuate and
recharge system.
1.
2.
3.
4.
5.
6.
7.
Short cycling of
compressor.
Faulty pressure control.
Loose wiring.
Thermostat.
TXV.
Capillary Tube.
Low charge.
Low evaporator air flow.
Faulty run capacitor.
Faulty internal overload.
1.
2.
3.
4.
5.
6.
7.
8.
9.
Replace pressure control.
Check unit wiring.
Located in supply air stream.
Differential setting too close.
Customer mis-use.
Internal foreign matter.
Power element failure.
Valve too small.
Distributor tube/tubes restricted.
Restricted with foreign matter.
Kinked.
I.D. reduced from previous compressor
failure.
Check system charge.
Dirty coil.
Dirty filter.
Duct too small or restricted.
Replace.
Replace compressor.
1.
2.
3.
4.
5.
6.
7.
8.
9.
Faulty compressor
valves.
Fast equalization/low pressure
difference.
1. Replace compressor and examine system
to locate reason.
1.
Electrical
Voltage present on load
side of compressor con-
tactor and compressor
won’t run.
Run capacitor.
Internal overload.
Compressor windings.
1.
2.
3.
Check with ohmmeter.
Allow time to reset.
Check for current ohms.
1.
2.
3.
Voltage present on line
side of compressor
contactor only.
Thermostat.
Compressor control circuit.
1.
2.
Check for control voltage to
compressor-contactor coil.
High pressure switch.
Low pressure switch.
Compressor turned off/on control or
interlock.
1.
2.

Classic HVPA & HVPSA M&S 8.09-1 15700 - 20 HVAC Equipment
Electrical (cont’d)
Problem/Symptom Likely Cause(s) Correction
No voltage on line side
of compressor contactor.
Blown fuses or tripped circuit breaker.
Improper wiring.
1.
2.
Check for short in wiring or unit.
Recheck wiring diagram.
1.
2.
Improper voltage. High voltage.
Low voltage.
Single phasing (3 phase).
1.
2.
3.
Power supply problem.
Power supply problem.
Wiring undersized.
Loose connections.
Check incoming power and fusing.
1.
2.
3.
Contamination
Moisture. Poor evacuation on installation or
during service.
1.
In each case, the cure is the same,
recover refrigerant. Add filter drier,
evacuate and recharge.
1.
High head pressure. Non-condensibles air.1.
Unusual head and
suction readings.
Wrong refrigerant.1.
Foreign matter -
copper fittings.
Copper tubing cuttings.1.
Copper oxide. Dirty copper piping.1.
Welding scale. Nitrogen not used.1.
Soldering flux. Adding flux before seating copper
part way.
1.
Excess soft solder. Wrong solder material.1.
Loss of Lubrication
Low suction pressure. Low charge.
Refrigerant leaks.
1.
2.
Check system charge.
Repair and recharge.
1.
2.
Cold, noisy compressor
- slugging.
Dilution of oil with refrigerant.1. Observe piping guidelines.1.
Noisy compressor. Migration.1. Check crankcase heater.1.
Cold, sweating
compressor.
Flooding.1. Check system charge.1.
Low load. Reduced air flow.
Thermostat setting.
1.
2.
Dirty filter.
Dirty coil.
Wrong duct size.
Restricted duct.
Advise customer.
1.
2.
Short cycling of
compressor.
Faulty pressure control.
Loose wiring.
Thermostat.
1.
2.
3.
Replace control.
Check all control wires.
In supply air stream, out of
calibration.
Customer misuse.
1.
2.
3.
Flooding
Poor system control
using a TXV.
Loose sensing bulb.
Bulb in wrong position.
Wrong size TXV.
Improper superheater setting.
1.
2.
3.
4.
Secure the bulb and insulate.
Relocate bulb.
Use correct replacement.
Adjust, if possible, replace if not.
1.
2.
3.
4.