Danfoss MLZ Series Instructions page 2

1 – Introduction
These instructions pertain to the MLZ / MLM scroll
compressors used for refrigeration systems. They provide
necessary information regarding safety and proper
usage of this product.
2 – Handling and storage
• Handle the compressor with care. Use the dedicated
handles in the packaging. Use the compressor lifting
lug and use appropriate and safe lifting equipment.
• Store and transport the compressor in an upright position.
• Store the compressor between -35°C and 70°C /
-31°F and 158°F.
• Don't expose the compressor and the packaging
to rain or corrosive atmosphere.
3 – Safety measures before assembly
Never use the compressor in a flammable atmosphere.
• Mount the compressor on a horizontal flat surface
with less than 7° slope.
• Verify that the power supply corresponds to the
compressor motor characteristics (see nameplate).
• When installing a compressor for R404A,
R507 R407A, R407F or R134a, use equipment
specifically reserved for HFC refrigerants which
was never used for CFC or HCFC refrigerants.
• Use clean and dehydrated refrigeration-grade
copper tubes and silver alloy brazing material.
• Use clean and dehydrated system components.
• The piping connected to the compressor must be
flexible in 3 dimensions to dampen vibrations.
• The compressor must always be mounted with the
rubber grommets supplied with the compressor.
4 – Assembly
• Slowly release the nitrogen holding charge
through discharge and suction ports.
• Connect the compressor to the system as soon as possible
to avoid oil contamination from ambient moisture.
• Avoid material entering into the system while
cutting tubes. Never drill holes where burrs
cannot be removed.
• Braze with great care using state-of-the-art
technique and vent piping with nitrogen gas flow.
• Connect the required safety and control devices.
When the schrader port, if any, is used for this,
remove the internal valve.
• For parallel assemblies of the compressors in
version C8, contact Danfoss.
5 – Leak detection
Never pressurize the circuit with oxygen or dry
air. This could cause fire or explosion.
• Do not use leak detection dye.
• Perform a leak detection test on the complete system.
• The low side test pressure must not exceed 31 bar
/450 psi.
• When a leak is discovered, repair the leak and
repeat the leak detection.
6 – Vacuum dehydration
• Never use the compressor to evacuate the system.
• Connect a vacuum pump to both the LP & HP sides.
• Pull down the system under a vacuum of
500 µm Hg (0.67 mbar) / 0.02 inch Hg absolute.
• Do not use a megohmmeter nor apply power to
the compressor while it is under vacuum as this
may cause internal damage.
7 – Electrical connections
• Switch off and isolate the main power supply.
• All electrical components must be selected as per
local standards and compressor requirements.
• Refer to electrical connections details. For three
phase applications, the terminals are labeled T1, T2,
and T3. For single-phase applications the terminals
are labeled C (common), S (start), and R (run).
• Danfoss scroll compressors will only compress gas
while rotating counter-clockwise (when viewed
Danfoss can accept no responsibility for possible errors in catalogues, brochures and other printed material. Danfoss reserves the right to alter its products without notice. This also applies to products
already on order provided that such alterations can be made without subsequential changes being necessary in specifications already agreed.
All trademarks in this material are property of the respective companies. Danfoss and the Danfoss logotype are trademarks of Danfoss A/S. All rights reserved.
FRCC.PI.014.A4.02 - December 2014
from the compressor top). Since single-phase
motors will start and run in only one direction,
reverse rotation is not a major consideration.
Three-phase motors, however, will start and
run in either direction, depending on the phase
angles of the supplied power. Care must be taken
during installation to ensure that the compressor
operates in the correct direction.
• Use ø 4.8 mm / #10 - 32 screws and ¼" ring terminals
for the power connection with ring connect screw
terminal (C type). Fasten with 3 Nm torque.
• Use ø 6.3 mm tabs for quick connect spade
terminals (P type).
• Use a self tapping screw to connect the
compressor to earth.
8 – Filling the system
• Keep the compressor switched off.
• Keep the refrigerant charge below the indicated
charge limits if possible. Above this limit; protect the
compressor against liquid flood-back with a pump-
down cycle or suction line accumulator.
• Never leave the filling cylinder connected to the circuit.
Compressor models Refrigerant charge limit
MLZ / MLM015-019-021-026
MLZ / MLM030-038-045-048
MLZ / MLM058-066-076
9 – Verification before commissioning
Use safety devices such as safety pressure switch
and mechanical relief valve in compliance with both
generally and locally applicable regulations and
safety standards. Ensure that they are operational
and properly set.
Check that the settings of high-pressure
switches don't exceed the maximum service
pressure of any system component.
• A low-pressure switch is recommended to avoid
low pressure operation.
Minimum setting for R22 1.5 bar (absolute) / 22 psia
Minimum setting for R404A 2.8 bar (absolute) / 41 psia
Minimum setting for R407A 1.7 bar (absolute) / 25 psia
Minimum setting for R407F 1.9 bar (absolute) / 28 psia
Minimum setting for R134a 1.45 bar (absolute) / 21 psia
• Verify that all electrical connections are properly
fastened and in compliance with local regulations.
• When a crankcase heater is required, it must be
energized at least 24 hours before initial start-up
and start-up after prolonged shutdown.
• Please respect a 90 Nm ± 20 Nm for tightening
torque of all rotolock nut.
10 – Start-up
• Never start the compressor when no refrigerant is charged.
• Do not provide any power to the compresor
unless suction and discharge service valves are
open, if installed.
• Energize the compressor. It must start promptly.
If the compressor does not start, check wiring
conformity and voltage on terminals.
• Eventual reverse rotation can be detected by
following phenomena; the excessive noise, no
pressure differential between suction and discharge,
and line warming rather than immediate cooling.
A service technician should be present at initial
start-up to verify that supply power is properly
phased and that the compressor is rotating in the
correct direction. MLZ / MLM Scroll compressors are
designed to operate for a maximum of 150 hours
in reverse, but as a reverse rotation situation can
go unnoticed for longer periods, phase monitors
are recommended. For compressors MLZ / MLM
048 and larger, phase monitors are required for
all applications. Danfoss recommends phase
protection for residential compressors.
• If the internal overload protector trips out, it must cool
down to 60°C / 140°F to reset. Depending on ambient
temperature, this may take up to several hours.
11 – Check with running compressor
Check current draw and voltage. Measurement of
amps and volts during running conditions must be
taken at other points in the power supply, not in the
compressor electrical box.
• Check suction superheat to reduce risk of slugging.
• Observe the oil level in the sight glass (if provided)
for about 60 minutes to ensure proper oil return to
the compressor.
• Respect the operating limits.
• Check
Movements in excess of 1.5 mm / 0.06 in require
corrective measures such as tube brackets.
• When needed, additional refrigerant in liquid phase
may be added in the low-pressure side as far as
possible from the compressor. The compressor must
be operating during this process.
• Do not overcharge the system.
• Never release refrigerant to atmosphere.
• Before leaving the installation site, carry out
a general installation inspection regarding
cleanliness, noise and leak detection.
3.6 kg / 8 lb
• Record type and amount of refrigerant charge
5.4 kg / 12 lb
as well as operating conditions as a reference for
7.2 kg / 16 lb
future inspections.
12 – Maintenance
Internal pressure and surface temperature
are dangerous and may cause permanent injury.
Maintenance operators and installers require
appropriate skills and tools. Tubing temperature may
exceed 100°C / 212°F and can cause severe burns.
Ensure that periodic service inspections to
ensure system reliability and as required by local
regulations are performed.
To prevent system related compressor problems,
following periodic maintenance is recommended:
• Verify that safety devices are operational and
properly set.
• Ensure that the system is leak tight.
• Check the compressor current draw.
• Confirm that the system is operating in a way
consistent with previous maintenance records
and ambient conditions.
• Check that all electrical connections are still
adequately fastened.
• Keep the compressor clean and verify the absence
of rust and oxidation on the compressor shell,
tubes and electrical connections.
• Acid / moisture content in system and oil should
be checked regularly.
13 - Warranty
Always transmit the model number and serial
number with any claim filed regarding this product.
The product warranty may be void in following
cases:
• Absence of nameplate.
• External modifications; in particular, drilling,
welding, broken feet and shock marks.
• Compressor opened or returned unsealed.
• Rust, water or leak detection dye inside the compressor.
• Use of a refrigerant or lubricant not approved by Danfoss.
• Any deviation from recommended instructions
pertaining to installation, application or maintenance.
• Use in mobile applications.
• Use in explosive atmospheric environment.
• No model number or serial number transmitted
with the warranty claim.
14 – Disposal
Danfoss recommends that compressors
and compressor oil should be recycled by
a suitable company at its site.
© Copyright Danfoss | Commercial Compressors | 2014.12
all tubes for abnormal vibration.