1 - Introduction
These instructions pertain to the VZH Variable
Speed scroll compressors used for A/C 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 55°C.
• Don’t expose the compressor and the packa-
ging to rain or corrosive atmosphere.
3 – Safety measures before assembly
Never use the compressor in a flammable
atmosphere.
• The compressor ambient temperature may
not exceed 50°C during off-cycle.
• Mount the compressor on a horizontal flat
surface with less than 3° slope.
• The compressor can only be supplied by a
frequency converter. Make sure that the frequency
converter is the dedicated one for the compressor
(power size and voltage: input & output).
Parameter 1.13 of the frequency converter lists the
possible combinations of compressors, frequency
converters and refrigerants.
• When installing a VZH, use equipment specifi-
cally reserved for HFC refrigerants which was
never used for CFC 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.
• Make sure the installation is equipped with
high-pressure safety components (e.g. pressure
switch, pressure relief valve) to prevent against
the bursting of pressure-containing compo-
nents.
4 - Assembly
• Slowly release the nitrogen holding charge
through the schrader port.
• 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 tech-
nique and vent piping with nitrogen gas flow.
• Connect the required safety and control de-
vices. When the schrader port is used for this,
remove the internal valve.
5 – Leak detection
Never pressurize the circuit with oxygen or
dry air. This could cause fire or explosion.
• Do not use dye for leak detection.
• Perform a leak detection test on the complete
system.
• The low side test pressure must not exceed 30 bar.
• 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.
• Evacuate the system to a pressure of 500 µm
Hg (0.67 mbar) 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.
See previous page for wiring details.
• The compressor is protected against excess
current by the frequency converter. Follow local
regulations regarding power line protection.
The compressor must be connected to ground.
• All electrical components must be selected as per
local standards and compressor requirements.
• Please refer to drawings for typical wiring connec-
tions and examine the specific wiring diagram
located in the frequency converter package. For
further details, refer to the application guidelines.
• Follow very closely the installation instruction
for the frequency converter:
- Mounting: The base frame of the frequency
converter must be very well fixed to the
support to ensure a very good continuity
between the ground potential of all electrical
panels and electrical boxes of the system.
- Wiring: All control wires have to be of a screee-
ned design. The cable for electrical motor sup-
ply has to be of a shielded design as well. Cor-
rect earthing of the shield cover has to be done
using the method shown on drawings, every
time this one has to be earthed on each end
of the cables. Distinct cable trays must be used
for control and motor supply.
• The frequency converter ensures direct motor
protection and the factory set parameters are
such to protect the motor over all current mal-
functions. An external overload is not necessary.
• Set the frequency converter parameters in
accordance with Danfoss recommendations
for the CDS303 frequency converter and VZH
variable speed compressor.
8 – Filling the system
• Keep the compressor switched off.
• Fill the refrigerant in liquid phase into the
outlet side of the condenser or liquid receiver.
The charge must be as close as possible to the
nominal system charge to avoid low pressure
operation and excessive superheat.
Compressor
Refrigerant charge limit (kg)
VZH088
5.9
VZH117
7.9
VZH170
13.5
Above this limit; protect the compressor against
liquid flood-back with a pump-down cycle not
lower than 2.3 bar (g) or a suction line accumu-
lator.
• Never leave the filling cylinder connected to
the circuit to avoid overfilling.
9 – Verification before commissioning
Use safety devices such as safety pressure
switch and mechanical relief valve in compliance
with both generally and locally applicable regu-
lations and safety standards. Ensure that they
are operational and properly set.
Check that the settings of high-pressure
switches and relief valves don’t exceed the
maximum service pressure of any system com-
ponent.
• A low-pressure switch is mandatory to avoid
vacuum operation. Minimum setting 1.5 bar (g).
• Verify that all electrical connections are properly
fastened and in compliance with local regula-
tions.
• The crankcase heater function is factory preset
to "disabled". It must not be used for VZH170 but
could be used for VZH088/117. In default case, an
external crankcase heater is required.
• After comissioning it is strongly recommended to
keep the frequency converter always energized.
10 – Start-up
• All service valves must be in the open position.
• Balance the HP/LP pressure.
• Energize the compressor. It must start promptly.
• If the compressor doesn’t start, verify that the
compressor is hooked up to the frequency
converter; check the power lead connections.
If these verifications reveal no abnormality,
check the motor windings with an ohmmeter.
• Check the frequency converter control pa-
nel: If any alarm is displayed check the wiring
and in particular the polarity of the control
cables. If an alarm is shown, refer to the fre-
quency converter application manual. Verify
in particular the combination of compressor,
frequency converter and refrigerant.
• Check current draw and voltage levels on the
mains. The values for the compressor elec-
trical motor can be directly displayed on the
frequency converter control panel.
• The optimum compressor suction superheat
is around 6K. The maximum allowed super-
heat is 30K.
11 – Check with running compressor
• Check current draw and voltage.
• Check suction superheat to reduce risk of
slugging.
• Observe the oil level at start and during opera-
tion to confirm that the oil level remains visible.
Excess foaming in oil sight glass indicates refri-
gerant on the sump.
• Monitor the oil sight glass for 1 hour after sys-
tem equilibrium to ensure proper oil return to
the compressor. This oil check has to be done
over the speed range to guarantee:
- a good oil return at low speed with mini-
mum gas velocity.
- a good oil management at high speed
with maximum oil carry over.
• Respect the operating limits.
• Check all tubes for abnormal vibration. Move-
ments in excess of 1.5 mm require corrective
measures such as tube brackets.
• When needed, additional refrigerant in the
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 the atmosphere.
• Before leaving the installation site, carry out
a general installation inspection regarding
cleanliness, noise and leak detection.
• Record type and amount of refrigerant charge
as well as operating conditions as a reference for
future inspections.
• Compressor failure to build up pressure: Check
all bypass valves in the system to ensure that
none of these has 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 compressor sump temperature. The
sump should be at least 6K above the satura-
ted suction temperature under steady-state
operating conditions.
• The high-pressure switch trips out: Check
condenser operations (condenser cleanliness,
fan operation, water flow and water pressure
valve, water filter, etc.). If all these are OK,
the problem may be due to either refrige-
rant 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
FRCC.EI.024.A1.02 © Danfoss Commercial Compressors 10/12
3
Instructions
