If oil return continues to perform poorly, further
investigation of the piping design is required.
• In all cases, the application limits of the compressor
must be respected; moreover, high superheat
values lead to high discharge temperatures and
decrease compressor capacity. The maximum
discharge temperature is 130°C: operating ata
higher temperature may result in refrigerant
decomposition.
• Under steady-state operating conditions, check
refrigerant piping or capillary tubes for abnormal
vibrations (refrigeration line movement in excess
of 1.5 mm necessitates corrective actions, pipe
brackets, etc.).
• Ensure that refrigerant flow through the liquid
line sight glass (when mounted) is adequate and
that operating temperatures correspond with
system specifications.
• When needed, refrigerant may be added in the
liquid phase, carefully throttling the refrigerant on
the low-pressure side and as far as possible from
the compressor.The compressor must be operating
during this process.
Do not overcharge the system.
11 - Troubleshooting
•
Compressor failure to start:
verify that the
compressor is hooked up to the power supply;
check the power lead connections and all suitable
capacitors on single-phase models. If these
verifications reveal no abnormality, control the
motor windings with an ohmmeter.
Note: when the internal motor protector has tripped
out, it may take up to several hours to reset and
restart the compressor.
•
Compressor failure to build up pressure:
check to make sure that all bypass valves in the
system have not been opened. Also check that all
solenoid valves are in their proper position. If the
internal pressure relief valve is open, the compressor
sump will be warm and the compressor will trip
out on the motor protector. If this happens, it may
take up to 2 or 3 hours to reset and automatically
restart the compressor.
•
Abnormal running noise on the system:
- Ensure the absence of any liquid flood-back
to the compressor by means of measuring
the return gas superheat and compressor sump
temperature. The sump should be at least 10K
above the saturated suction temperature under
steady-state operating conditions.
- Check that the fans are running free and without
vibration.
•
The high-pressure switch trips out:
check
condenser operations (condenser cleanliness,
fan operations, etc.). If above check out OK,
the problem may be due to either refrigerant
overcharging or the presence of a non-condensable
(e.g. air, moisture) in the circuit.
•
The low-pressure switch trips out:
check
evaporator operations (coil cleanliness, fan
operations, water flow, water filter, etc.), liquid
refrigerant flow and pressure drops (solenoid valve,
filter dryer, expansion valve, etc.), refrigerant charge.
•
Low refrigerant charge:
the correct refrigerant
charge is given by the liquid sight glass indication,
the condenser delta T in relation to the refrigerant
pressure tables (pressure-temperature), the
superheat and the sub-cooling, etc. (if additional
charge is deemed necessary, refer to the «Filling
the system» section).
• Compressor maximum short cycling:
there
must be a minimum delay of five minutes between
two compressor starts. DCC recommends the
compressor should run at least two minutes after
each start, and between each stop and start must
be three minutes standstill. Only during pump
down cycle, the compressor may run much shorter
until the pumpdown pressure has been reached
or when safety devices will prohibit compressor
further operation.
12 - Maintenance
• Proper operations and maintenance of the
condensing units serve to prevent against
system-related problems. The following preventive
maintenance checks, to be performed at regular
intervals, are highly recommended:
- Control operating conditions (evaporating
temperature, condensing temperature,
compressor discharge temperature, temperature
difference on heat exchangers, superheat,
sub-cooling). These conditions must always
remain within compressor operation limits.
- Verify that safety devices are operational and
properly set.
- Check the compressor oil level and quality; this
step may include an acid test, humidity check,
spectrometer analysis, etc. whenever the oil
becomes discolored.
- Ensure that the circuit is leak tight.
- Verify the proper operation of heat exchangers
and, if necessary, clean them.
- Check that the fans are running free (without
vibration) and current draw on the compressor
motor as well as proper voltage balance
between phases.
- Change the filter dryer when necessary.
- Check that all electrical connections are still
adequately fastened.
- Make sure the condensing unit is clean and in
good working order; verify the absence of rust
or corrosion on components under pressure
and electrical connections.
- Make sure the refrigerant charge is suitable for
both winter and summer operation.
• Ensure that periodic in-service inspections
required by local regulations are performed.
13 - Replacement
Precaution must be taken when disconnecting
any components, cutting or drilling holes in the
tubing to ensure that no refrigerant under pressure
is present in the system.
The refrigerant shall not be discharged directly
into the atmosphere; rather, it must be removed
using approved reclamation techniques and
equipment and then safely stored, inaccordance
with applicable legislation.
The presence of refrigerant vapor can displace
air and lead to suffocation. Proper ventilation
is mandatory at all times when servicing the
equipment.
A condensing unit component change must be
carried out in compliance with local regulations.
• Make sure that the main power supply has been
switched off.
• Before replacement, it is necessary to determine
the cause of failure and implement remedial
action. If such analysis and repair are not performed,
repetitive failure may occur. Note that an oil acidity
test always proves helpful indiagnosis when
undertaking compressor replacement.
• Check that the replacement component has the
same electrical and refrigeration performance
characteristics as the original one.
• Whenever piping needs to be modified, please
refer to the «
Safety measures prior to assembly
»
section.
• For further details on replacement steps,refer to
the previous sections of this manual.
Note:
In the event of compressor motor failure,
flush and clean the entire circuit before replacing
the compressor in order to remove acids and
contaminants. Systematically install a new filter
dryer on the liquid line. Prior to this step (if
necessary), run the system for at least 2 hours
with anti-acid cartridges (in such instances, the
installation of a suction filter might also be required).
After an operating period of approximately 2 weeks,
check the level of oil acidity. If the oil acid test
proves positive, drain and replace the oil, replace
the anti-acid liquid line filter dryer cartridges and
the suction filter previously installed. Repeat oil
and filter dryer replacements until the system is
clean and acid-free.
When there is no longer any sign of acidity, replace
the anti-acid cartridges by the standard model and
remove the suction strainer cartridge as required.
14 - User advisory
Insist that all service operations only be
performed by qualified personnel.
The condensing unit tubing and compressor
surface temperatures may exceed 100°C (212°F)
and cause severe bodily burns. Special precaution
must be taken when working around the compressor
and refrigerant tubing. Moreover, a compressor
in operation can generate very cold surface
temperatures (as low as -45°C / -49°F), there by
exposing personnel to the risk of freezing burns.
Pressure inside the compressor and refrigerant
circuit can reach dangerously high levels (e.g.
abnormal operation, fire,…) leading to personnel
injury if suddenly released; therefore, never drill,
weld or cut the compressor shell and adjacent
tubing (release of liquid refrigerant can cause
flash freezing on exposed skin).
Even though fans are fitted with safety guard
it is recommended not to work on condenser
while fans are running.
Be aware that the product warranty may be
deemed null and void in the following cases:
• Modifications to the unit, unless approved by
Danfoss Commercial Compressors, absence of
nameplate, broken or dented components, shock
marks, etc...
• Compressor opened by the customer or returned
unsealed (i.e. open discharge or suction ports),
• Presence of rust or water inside the condensing
unit circuit,
• Addition of leak-detection fluid in the compressor
lubricant,
• Use of a refrigerant or lubricant not approved by
Danfoss Commercial Compressors.,
• Any deviation from recommended instructions
pertaining to installation, application or maintenance,
• Use in mobile applications (boats, trains, trucks,
etc.) or under explosive atmospheric conditions.
The date of production of the condensing unit is
indicated on the nameplate. Ensure that the model
and serial number information is always transmitted
with any claim filed regarding this product.
Instructions
6
8510198 P03-A © Danfoss Commercial Compressors 03/05
