8510223 P01-A © Danfoss Commercial Compressors March 2006
Instructions
main. The values for the compressor electrical
motor can be directly displayed on the frequency
converter control panel.
• Monitor the oil sight glass for 60 min. after
system equilibrium to ensure proper oil return
to the compressor. This oil check has to be done
over the speed range to garanty:
- a good oil return at low speed when gas velo-
city is at it’s minimum,
- a good oil management at high speed where
oil carry over is at it’s maximum.
• Suction superheat setting: Optimal compressor
suction superheat would be around 10K, with the
maximum allowable superheat being 30K.
• 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 at a 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.).
• After 2 to 4 hours of operations under
established conditions, check the oil level and
add oil if necessary (refer to TI 2-025). If oil return
continues to perform poorly, further investigation
of the piping design is required.
• 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 at a medium speed
if possible (this can be manually hand forced at
50 Hz for exemple).
Do not overcharge the system.
11 – Troubleshooting
• Compressor failure to start: Verify that the
compressor is hooked up to the frequency
converter; check the power lead connections. If
these verifications reveal no abnormality, control
the motor windings with an ohmmeter.
• Check the frequency converter control panel:
If any alarm is displayed check the wiring and
specially the polarity of the control cables,
when an alarm is shown refer to the converter
application manual and specially revue the
electrical motor parameters set in.
• 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.
• Abnormal running noise: Ensure the absence of
any liquid flood-back to the compressor by means
of measuring the return gas superheat and com-
pressor sump temperature. The sump should be at
least 10K above the saturated suction temperature
under steady-state operating conditions.
• The high-pressure switch trips out: Check
condenser operations (condenser cleanliness,
fan operations, water flow and water pressure
valve, water filter, 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 evapo-
rator 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 indica-
tion, the condenser delta T in relation to the re-
frigerant pressure tables (pressure-temperature),
the superheat and the sub-cooling, etc. (if addi-
tional charge is deemed necessary, refer to the
“Filling the system” section).
• Compressor short cycling: The number of cycles
shall never exceed 12 starts per hour.
12 - Maintenance
• Maneurop® compressors do not necessitate any
special maintenance procedure. However, it must
be recalled that proper operations and mainte-
nance of the system serve to prevent against sys-
tem-related compressor problems. The following
preventive maintenance checks, to be performed
at regular intervals, are highly recommended:
- Control operating conditions (evaporating
temperature, condensing temperature, compres-
sor discharge temperature, temperature differen-
ce 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 qua-
lity; 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 exchan-
gers and, if necessary, clean them.
- Check the current draw on the compressor motor
as well as proper voltage balance between phases.
- Check that all electrical connections are still
adequately fastened.
- Make sure the compressor is clean and in good
working order; verify the absence of rust on the
compressor shell, piping and electrical connections.
- Make sure the refrigerant charge is suitable
for both winter and summer operations.
• Insure that periodic in-service inspections
required by local regulations are performed.
• For the frequency converter check the internal
temperature on the display and control the
proper air flow for cooling.
• Fault are logged on the converter memory and
can be displayed, this can help to revue some
parameter of the frequency converter or of the
system itself.
13 – Replacement
Precaution must be taken when disconnec-
ting, cutting or drilling holes in the tubing to en-
sure 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, in accordance
with applicable legislation.
The presence of refrigerant vapor can displace
air and lead to suffocation. Proper ventilation is man-
datory at all times when servicing the equipment.
A refrigeration system 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 determi-
ne the cause of failure and implement remedial
action. If such analysis and repair are not perfor-
med, repetitive failure may occur. Note that an
oil acidity test always proves helpful in diagnosis
when undertaking compressor replacement.
• Don’t forget to use the fault memory of the
frequency converter and to recover the fault
descriptions before initializing the system and
even shutting off the power
• Check that the new Maneurop® compressor and
the on-site compressor to be replaced display the
same electrical and refrigeration performance
characteristics.
• Use the rubber grommets and gaskets supplied
with the new compressor.
• 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.
• Danfoss recommends not to throw away a used
compressor but to dispose of the com-
pressor and its oil at a specialised recycling
company site.
Note:
In the event of 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 compressor and tubing 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), thereby exposing personnel to the risk of
freezing burns.
Pressure inside the compressor can reach dange-
rously high levels (e.g. abnormal operation, fire,…)
leading to personnel injury if suddenly released; the-
refore, never drill, weld or cut the compressor shell
and adjacent tubing (release of liquid refrigerant can
cause flash freezing on exposed skin).
Be aware that the product warranty may be
deemed null and void in the following cases:
• external modifications to the compressor (ab-
sence of nameplate, drilling, welding, broken
feet, shock marks),
• compressor opened by the customer or returned
unsealed (i.e. open discharge or suction ports),
• presence of rust or water inside the compressor,
• addition of leak-detection fluid in the lubricant,
