Although this blog post describes the
troubleshooting and working principles of Haier Central Air-conditioning
system; it can be taken as a referral document to all air conditioners, as all
of it are working on same principle; provided some minor changes; very like
Refrigerators.
HAIER - HR18D1VAR _ HR24D1VAR _
HR36D1VAR _ HR48D1VAR _ HR30D1VAR _ HR42D1VAR _ HR60D1VAR
SERVICE VALVES
There are two types of service valve
used on these air conditioning units. They are the service port valve or “Schrader valve” and the refrigerant line valve. The Schrader
valve is like a valve in an automobile tire.
The stem or core is removable with a flexible seal at its base held
closed with a spring. Schrader valves allow a technician to connect gages to
the system with a minimum loss of charge. Use a cap with an inner seal to
prevent leakage and keep dirt and moisture from entering the system. Refrigerant control valves allow the outdoor
unit to be isolated into from the balance of the system. In split systems,
these valves also hold the charge in the outdoor section from factory.
THERMOSTATS
Thermostats are the most obvious
control in the air conditioning system because these controls are accessible by
the consumer. Contact your local distributor for information on part numbers of
various manual changeovers, auto changeover and set-back thermostats or see the
thermostat and sub base selection information found in the wiring diagram
booklet. In the cooling mode, the
thermostat calls for cooling by energizing the compressor contactor and the
indoor blower control. The indoor blower can operate continuously by setting
the thermostat sub base fan switch to the “ON” position.
PROTECTION DEVICES
Protection for the unit begins with the installation of appropriate fuses or
circuit breakers by the installing contractor. Breaker or fuse size is governed
by the National Electrical Code and local code. AMP draw requirements for each
unit are found in the Specifications.
OVERLOADS AND LIMITS
Overloads protect against over-current
or over-temperature conditions. Those located in the outdoor unit include the
automatic reset internal overload in the fan motor and the compressor automatic
reset internal overload. Such controls are not serviceable but their operation
may influence service troubleshooting .For example, the compressor internal
overload may stay open for several hours .A technician may incorrectly diagnose
this as an open compressor winding.
HIGH PRESSURE CUT OUT SWITCH
The high pressure cut-out is a pressure
activated switch. It opens an electrical circuit when the refrigerant pressure
exceeds a pre-determined limit of 440 to 460 p.s.i.g. When pressure becomes normal, the switch
restores automatically.
RELAYS
Relays provide a method for control
switching. Relays may switch either low(24VAC) or line voltage. Generally relays used in air conditioning use
24VAC coils. Contact voltage may be either low or line voltage.
COMPREESSOR CONTACTOR
The coil uses 24Volts but the contacts
carry line voltage. The heater contactor
is a large relay which controls the compressor and the outdoor fan operation.
Some contactor use single pole contacts, while others use 2-pole or 3-pole
contacts. Single-pole contactors break
only one side of the power feed to the compressor and outdoor fan. The other
side remains connected to the power source. The 2-pole or 3-pole contactor
breaks power to all sides of the compressor and outdoor fan.
CAUTION: WHEN THERE IS A SINGLE POLE
CONTACTOR, ONE SIDE OF A 240 V.A.C.CIRCUIT REMAINS HOT. THIS MEANS THAT THE
WIRING IN THE HIGH VOLTAGE CIRCUIT MAY HAVE A POTENTIAL OF 120V.A.C.TO GROUD.
BEFORE SERVICING THE UNIT, ALWAYS TURN OFF POWDER AT THE UNIT DISCONNECT
SWITCH.
OPTIONAL DELAYS AND KITS
A Time-Delay in the compressor
contactor low control circuit allows time for system pressure to equalize
before re-starting the compressor.
This delay uses solid state circuitry
to measure the time since the power was interrupted and is set for
approximately 3 minutes. It is not field adjustable. This is a delay on break
timer.
START KITS
This special relay uses the EMF
generated by the compressor start windings to take a start capacitor out of the
circuit. The relay and its companion capacitor can start the compressor at low
voltages and against higher pressure, such as those caused by non-bleed port
expansion valves. Start kit components
should match the recommended ratings and functions of those provided by the
reciprocating compressor manufacturer. Start kits are not
normally required with scroll compressors. The operating characteristics of the
scroll compressor make a start kit unnecessary.
REFRIGERANT SYSTEM DIAGRAM
SYSTEM STARTUP
Turn thermostat to "OFF", turn on power supply at
disconnect switch.
Turn temperature setting above the room temperature.
Turn fan switch to "ON". Indoor blower should run. Be
sure it is running in the right direction.
Turn fan switch to "AUTO". Turn system switch to
"COOL" and turn temperature setting below room temperature. Unit
should run in cooling mode.
Check to see if compressor and outdoor fan are running
correctly.
Check the refrigerant charge.
Replace service port caps. Service port cores are for system
access only and will leak if not tightly capped.
Check unit for tubing and sheet metal rattles.
SEQUENCE OF OPERATION
In order to service and troubleshoot a air conditioning system,
The service technician must understand the system’s sequence of operation. This
is the order of events the system undergoes in response to. Understanding the
sequence of operation aid in determining where to start troubleshooting when
the unit doesn’t operate properly. Deviation from the normal operation sequence
will provide clues to system problems.
COOLING CYCLE Mechanical.]
The compressor provides high pressure, superheated refrigerant
vapor.
The vapor leaves the compressor and passes through the reversing
valve.
The vapor flows through the outdoor vapor line to the finned
outdoor coil. Air from the outdoor fan removes heat from the refrigerant vapor.
When enough heat is removed, the vapor condenses into a high pressure liquid.
The liquid temperature leaving the outdoor coil is slightly warmer than ambient
air temperature.
This warm, high pressure liquid leaves the outdoor coil, and
flows through the small copper refrigerant liquid line.
At the end of the liquid line, the
refrigerant passes through a fixed metering device, reducing pressure and
temperature .
The liquid, under reduced pressure,
then enters the indoor coil surface it expands and absorbs heat from the indoor
air passing over the finned surface. Heat from the indoor air, causes the low
pressure liquid to evaporate and cool the indoor air. The refrigerant has now
been converted to cool vapor.
The cool refrigerant vapor travels
through the larger, insulated vapor line to the accumulator.
The accumulator separates any liquid
refrigerant and holds it. Only vapor refrigerant and refrigerant oil leave the
accumulator. The oil is drawn out through a special port inside the
accumulator.
Refrigerant vapor flows through the
suction line to the intake of the compressor. The cycle then repeats.
COOLING CYCLE [Electrical]
The thermostat calls for cooling when
the space temperature is above the set point.
This sends a 24 voltage signal through
the “Y” terminal to the outdoor unit PCB, after 3 minutes the compressor
contact in the outdoor unit are closed. The compressor and outdoor fan start.
At the same time, a 24 Voltage signal
flows through the “G” Terminal to the air handler PCB and indoor blower starts.
The cooling system is now in operation.
The thermostat satisfies and ends the
call for cooling.
This ends the 24 Voltage signal to the
compressor start kit and the outdoor unit stops.
This ends the 24 voltage signal to the
indoor blower relay and this indoor blower strips.
The system is now off.
COMPRESSOR ELECTRICAL CHECKS
Single-phase compressors use permanent
split capacitor motors. There are two winding that connect at a common point at the “common” wiring terminal. The two winding are called “start” and
"run". The start winding has the higher resistance and is connected
in series with the capacitor. The run winding has the lower resistance and
connects directly to the power supply from the compressor contactor.
If compressor draws high amperage, for
an unusually long time or temperatures in the compressor motor, it opens an internal circuit to stop the motor.
ELECTRICAL CHECK COMPRESSORS
Confirm that all electrical wiring for
the units is correct and that all wiring connections are right.
Measure the available line
voltage. On the single phase 208/230Volt
units this should be from 197 to 253 Volts.
Check for proper control voltage at the
unit contractor coil. If this voltage is inadequate or is not present, refer to
the wiring diagram or the compressor troubleshooting flow chart at the end of
this section for possible causes.
Disconnect all power from the unit and
visually inspect the compressor contactor for pitted or burned contacts.
This could indicate high or low voltage
problems or improper start components.
Check the contactor coil with an ohmmeter for a short or open circuit.
Replace the contactor if any fault is noted.
WITH THE ELECTRICAL POWER OFF, remove
all power wires from the compressor terminals, MARK THE ORIGINAL LOCATION OF
EACH WIRE.
A Use an ohmmeter set for the highest
scale to check for grounding between compressor motor terminals and a good
clean ground such as the compressor shell or copper line.
The resistance from any terminal to
ground should exceed 1,000,000 ohms.
Use an ohmmeter set for the lowest
scale and check the continuity of the motor windings .These ohm values are less
than ten ohms and in some cases less than one ohm.
The ohm reading from the RUN terminal
to common terminal is the lowest reading measured between. Compressor
terminals, approximately 1 ohm.
The ohm reading from the Start TERMINAL
TO COMMON TERMINAL will be the middle ohm value measured between the terminals
and be approximately 2.0 to 3.0 ohms.
The ohm reading from the Start TERMINAL
TO run terminal will be the highest ohm value of the three measurements and
will be approximately the sum of the first two measurements.
The resistance from one winding
terminal to any other terminal should be the same with three phase compressors.
NOTE: on larger 208/230 volt compressors the ohm values could be as low as 0.10
ohms, THIS IS NOT A SHORTED WINDING .A winding is open if resistance measured
is infinite.
Compressors fail mechanically due to
bearing failure, valve failure, or damage to the internal suspension system.
Bearing and valve failure is almost always caused by liquid refrigerant.
COMPRESSORS ARE DESIGNED TO ONLY PUMP REFRIGERANT VAPOR. Liquid refrigerant
damages the valves by deforming or breaking them. Liquid refrigerant also
damages bearings by diluting or foaming the lubricating oil.
SYSTEM PUMP DOWN
This procedure tests the compressor
valves. It can indicate internal refrigerant leaks such as through the liquid
line service valve. The procedure uses the compressor to trap the entire
refrigerant inside the condensing coil (outdoor cooling). The technician’s
gauges indicate if the condensing coil holds the refrigerant as intended or if
it leaks out.
Procedure
Connect the compound refrigerant gauge
to a service port that reads suction pressure such as on the compressor shell,
or in the line between accumulator and compressor. Connect the high pressure
gauge to a service port that reads high pressure.
With the unit operating, front seat
(close) the liquid line service valve. Observe the gauges .The suction pressure
should fall. The high pressure should also fall slightly. If the discharge
pressure rises above 400 psi, shut off about outdoor unit.
SHUT OFF THE COMPRESSOR WHEN THE
SUCTION PRESSURE DROPS TO 3-5 PSI. POSITIVE PRESSURE. DO NOT OPERATE THE
COMPRESSOR WITH A NEGATIVE SUCTION PRESSURE OR IN A VACUUM.
After pump down and compressor stops,
observe the suction pressure on the compound gauge.
The suction pressure holds as steady pressure. this is a normal condition.
Suction pressure rises above the
stopping point, but then stops and holds steady. Some refrigerant finally
evaporating in the coil, and registering on the gauge. This is the normal
condition.
Suction pressure conditions rise and
eventually equalizes with the observed pressure on the high pressure gauge.
Abnormal condition.
Refrigerant is leaking from the
condenser coil.
Causes: Leaking liquid line valve,
leaking discharge check valve (scroll compressors only ), leaking compressor
valves.
Determine the causes and correct it.
Unable to reach the 3-5 PSI level for
suction pressure. This is an abnormal condition. Refrigerant is leaking from the condenser coil .
Causes: Leaking liquid line valve,
leaking discharge check valve (scroll compressors only ), leaking compressor
valves.
Determine the causes and correct it.
SYSTEM REFRIGERANT NONCONDENSIBILES
CHECK
This procedure checks the quality of
the refrigerant by comparing the refrigerant pressure to its temperature. The
test tells if there are contaminating non-condensable gases in the refrigerant,
usually air or moisture.
Disconnect the compressor by REMOVING
EACH WIRE FROM THE COMPRESSOR TERMINALS.
MARK AND IDENTIFY THE WIRE TERMINALS WITH THE COPRESPONDING WIRE COLOR CODE.
Close the disconnect switch to the
system and run the condensing fan .Measure the condensing coil entering and
leaving air temperature with accurate thermometers.
Run the condensing fan until the
leaving air temperature equals to the entering air temperature. This is now the
refrigerant temperature.
Compare the observed refrigerant
pressure shown on the high pressure gauge to its associated pressure on a
temperature –pressure conversion chart.
The refrigerant pressure should equal
the chart pressure for the observed temperature.
The system pressure is above the chart
pressure. Capital letters: Non-condensates are present -air and/or moisture.
ACTION: Remove and recover the refrigerant. Evacuate the system and charge with
new and correct refrigerant.
The system pressure is below the chart
pressure. Capital letters: A mixed refrigerant is present. ACTION: Remove and recover the refrigerant. Evacuate the system
and charge with new and correct refrigerant.
COMPRESSOR REMOVAL PROCEDURES
USE THESE PROCEDURES ONLY WHEN YOU HAVE
POSITIVELY DETERMINED THAT THE COMPRSSOR HAS EXPERIENCED A MECHANICAL AND/OR
ELECTRICAL FAILURE.
CAUTION: After a severe motor burn-out
the products of the burn-out may be acidic. The technician should wear rubber
gloves and eye protection to prevent injury when testing refrigerant oil.
DISCONNECT THE MAIN POWER SOURCE TO THE
UNIT AND LOCK THE DISCONNECT SWITCH IN THE OPEN POSITION.
Disconnect the electrical wiring at the
compressor identifying each wire and its location.
Remove the refrigerant charge from the
entire system using proper recovery procedures.
Remove the failed compressor.
Unsolder the suction and discharge
lines at the compressor stubs.
Remove the compressor hold down bolts.
Place the failed compressor on a smooth
surface to remove the mounting grommets and sleeves for use with the new
compressor .
Prevent any contamination from entering
the refrigerant lines.
Conduct an acid test on the oil from
the failed compressor.
Secure a generous sample of oil from
the failed compressor.
Follow the oil test kit instructions to determine the degree of compressor burn
out.
As a
general rule, oil with a test number less than 0.05 indicates a mild burn out.
Oil with a test number greater than
0.05 indicates a severe burn-out.
Some oil test kits indicate severity by
color change.
As a guide, burn out classifications is
as follows:
Oil clear, no color; the compressor may
have had a mechanical failure and not a burn-out.
Oil clear, slight color, the compressor
may have had a mild burn-out.
Oil very dirty, strong odor test >0.05,
the compressor may have had severe burn-out.
Note: Dispose of any contaminated
refrigerant oil in accordance with all environmental regulations and
procedures.
Use the following procedures with units
suspected of having mild to severe burn outs.
After compressor removal, insert a
clean, lint free swab into the system‘s suction and discharge lines to
determine the extent of contamination.
If contamination is noted for a
considerable depth, consider replacing the lines with new tubing.
Confirm that the new compressor has no
shipping damage. The line connections must come sealed from the factory. Verify
that the replacement compressor is the same model number and electrical
characteristics as the original.
Place the new compressor in the unit
and install the mounting bolts.
Remove the caps from the compressor
stubs, clean the lines and stubs, and braze joints together.
If any burn detected replace the liquid
line filter drier with an oversized core filter drier, if the burn was severe,
and a suction line filter drier.
Inspect all other components such as
check valve and electrical components for proper operation. Replace any if
necessary.
After all connections are made, open
the service valves and pressurize to 150 psi with dry nitrogen, Leak test with
liquid detergent. If a leak is found, repair it after removing the nitrogen,
and recheck.
After leak testing, recover any test
refrigerant.
Evacuate through both high and low side
connections to the system.
Evacuate to a level of 1500 microns
twice and 500 microns the last time.
Break each vacuum with dry nitrogen to
3.0 psi.
Use the largest connections and hoses
possible to expedite the process.
Charge with clean, new or reclaimed
R-22 refrigerant. Charge in accordance with proper charging procedures.
Re-check the system 24 hours of run
time to verify the unit is free of acid.
Other Check Points
Verify the operating voltage is within
the specified range.
Check that all wiring connections are
tight.
Verify that all fuses or circuit
breakers are of the proper type and operational.
Verify the air conditioning operates
properly in cooling.
Inspect all the other electrical
components for proper operation.
Verify the thermostat and sub base are
correct and operate properly.
Verify all ducts and air moving device are
sized and operate properly.
Verify the refrigerant piping is sized
correctly and not pinched
Verify all the system is in correct
position.
