System configuration .......................................................................................................................................................5
Tandem .................................................................................................................................................................................. 8
General requirements ...................................................................................................................................................... 9
General requirements ....................................................................................................................................................12
General requirements ....................................................................................................................................................14
General requirements ....................................................................................................................................................16
System evaluation ...........................................................................................................................................................17
Test, criteria and solutions ............................................................................................................................................ 17
System evaluation ...........................................................................................................................................................19
System evaluation ...........................................................................................................................................................21
Test, criteria and solutions ............................................................................................................................................21
Control logic ...................................................................................................................... 22
Safety control logic requirements .............................................................................................................................22
Short cycle protection....................................................................................................................................................22
Ordering information .....................................................................................................................................................25
ORDERING INFORMATION .............................................................................................. 25
The application guideline describes the operating
characteristics, design features and application
requirements for hybrid manifolding of the
Danfoss DSH fixed-speed compressor and the
VZH inverter compressor in air-conditioning and
heat pump applications.
To ensure proper parallel installation and running
conditions, the following recommendations must
be followed:
A parallel compressor installation refers to a
system of interconnected compressors with a
common suction line and a common discharge
line. The technique of mounting compressors
in parallel is also called manifolding. The hybrid
manifolding in this application guideline refers
to the manifolding of the Danfoss inverter
compressor (VZH) and fixed speed compressor
(DSH), which has several benefits.
• It is essential to respect all the instructions
given in these guidelines; please refer to
the instruction leaflet supplied with each
compressor and the application guidelines for
single compressors.
• For additional system components related to
specific application requirements, the supplier
recommendations must always be respected.
The main reason is reduced operating cost
through controlling capacity and power
consumption to a greater extent. This is achieved
by both staggering the compressor switch-on
sequences and regulating the speed of the
inverter compressor which allows the parallel
system to continuously match its power with the
capacity needed.
PRODUCT INFORMATIONSYSTEM DESIGNORDERING INFORMATIONGENERAL INFORMATION
Capacity
Compressor n°1
VZH 25-100 rps
A second reason for manifolding the inverter
compressor and the fixed speed compressor is
improved part-load efficiency. In the variable
speed+fixed speed parallel installation,
the system can run either only the inverter
compressor at lower load or both the inverter and
fixed speed compressors at a higher load with the
fixed speed compressor operating at 100% load.
Compressor n°1
VZH 25-100 rps
Compressor n°2
xed speed DSH
Therefore, it will be possible to achieve a higher
part-load efficiency.
Thirdly, the capacity of the hybrid manifolding
system can be widely regulated, for example 10%
to 100%. The continuous capacity regulation
allows for accurate temperature control and a
comfortable indoor environment.
4AB298632269085en-000401
Oil management concept
System configuration
Hybrid manifolding systems use the dynamic
system for oil balance. The suction connections
between the two individual compressors are
interconnected by a special suction separator
design that allows most of oil feed into variable
speed compressors.
Discharge line
VZH
VZH
DSH
DSH
An optical-electrical oil level sensor fixed in
a variable speed compressor monitors the
compressor oil level.
If the oil level drops below the limit, the OEM
main controller activates the oil management
logic.
Drive
ModBus
OEM main controller
GENERAL INFORMATIONSYSTEM DESIGNORDERING INFORMATIONPRODUCT INFORMATION
Oil equalization tubeSuction separatorSuction line
Optical oil
level sensor
5AB298632269085en-000401
Oil management concept
FS
Return
Gas
Oil-rich gas flow
Oil poor gas flow
VS
FSVS
GENERAL INFORMATIONSYSTEM DESIGNORDERING INFORMATIONPRODUCT INFORMATION
Downstream
compressor
Upstream
compressor
The hybrid manifolding system uses the dynamic
system for oil balance.
The suction connections of the two individual
compressors are interconnected by a suction
separator that integrates with the suction oil
separator and the gas restrictor. The variable
speed compressor (VS) is installed in the
upstream position which appears first on suction
line and fixed speed compressor (FS) is installed
on downstream position.
The oil which clings back along the main suction
line is separated by the suction separator which
Suction separator (Oil separator/gas restrictor)
returns most of the oil in the suction gas to the
upstream compressor. The suction separator
creates a slight pressure drop to ensure lower
sump pressure between two compressors are
well balance when fixed speed compressor
is ON and the inverter compressor is running
at maximum speed. When the variable speed
compressor runs at any frequency below
maximum speed, the sump pressure in the fixed
speed compressor is lower than the variable
speed compressor, and driven by the sump
pressure difference, the excess oil from the
variable speed compressor runs into the fixed
speed compressor sump.
6AB298632269085en-000401
Oil management concept
Approved hybrid tandem
configurations and
capacity range
Different configurations of hybrid tandems are possible. All VZH models (high/low pressure ratio/
different voltage) could be manifolded with fixed speed compressors.
Standard rating conditions: ARI standard Evaporating temperature: 7.2°C Superheat: 11.1k
Condensing temperature: 54.4°C Subcooling: 8.3k
Subject to modification without prior notification
Data given for motor code G compressor – for full data details and capacity tables, please refer to Coolselector2
www.coolselector.danfoss.com
FS: 50Hz, VS:100HzFS: 60Hz, VS: 100Hz
kWTRkWTR
GENERAL INFORMATIONSYSTEM DESIGNORDERING INFORMATIONPRODUCT INFORMATION
7AB298632269085en-000401
Dimensions
Tandem
GENERAL INFORMATIONSYSTEM DESIGNORDERING INFORMATIONPRODUCT INFORMATION
HH
D
L
Tandem modelComposition
VZH178 HVZH088+DSH090
VZH208HVZH088+DSH120
VZH257HVZH117+DSH140
VZH278HVZH117+DSH161
VZH301HVZH117+DSH184
VZH354HVZH170+DSH184
VZ H410HVZH170+DSH240
VZH465HVZH170+DSH295
Tandem configurations are achieved by assembling individual compressors
Outline drawing
number
85601561" 5/81" 3/81011445482
85601551" 5/81" 3/8811445482
85601541" 5/81" 3/81011445540
85601531" 5/81" 3/8811445540
85601521" 5/81" 3/81024445540
85601511" 5/81" 3/8811445540
85601521" 5/81" 3/81024445540
85601511" 5/81" 3/8811445540
85601501" 5/81" 3/8111 6445555
85601491" 5/81" 3/8811445555
856014 82" 1/81" 5/81241583682
85601472" 1/81" 5/8890583682
85562712" 1/81" 5/81245583682
85562702" 1/81" 5/8953583682
85562712" 1/81" 5/81245583682
85562702" 1/81" 5/8953583682
D
L
SuctionDischargeL (mm)D (mm)H (mm)
8AB298632269085en-000401
Design pipe
General requirementsProper piping practices should be employed to:
1. Ensure adequate oil return, even under
minimum load conditions (fixed speed
compressor off, variable speed compressor
at minimum speed, minimum evaporating
conditions). If minimum refrigerant velocity
cannot be reached, it is strongly recommended
that an oil separator is used. For a validation test,
the see section “Manage oil in the circuit”.
To condenser
0.5% slope
max. 4 m
max. 4 m
4 m/s or more
U-trap, as short as possible
8-12 m/s
Evaporator
0.5% slope
4 m/s or more
2. Prevent condensed liquid refrigerant from
draining back into the compressor when
stopped (discharge piping upper loop). For
validation tests, see the section “Manage off-cycle
migration”.
General recommendations are described in the
figures below:
GENERAL INFORMATIONPRODUCT INFORMATIONORDERING INFORMATIONSYSTEM DESIGN
HP
LP
U trap, as short as possible
Upper loop
HP
LP
3D flexibility
3. Piping should be designed with adequate
three-dimensional flexibility to avoid excess
vibration. It should not be in contact with the
surrounding structure, unless a proper tubing
mount has been installed. For more information
Condenser
on noise and vibration, see the section “Sound
and vibration management” in the application
guideline for Danfoss VZH Gen3 scroll
compressors (AB300034185311en).
9AB298632269085en-000401
Design pipe
Suction on leftSuction on right
GENERAL INFORMATIONPRODUCT INFORMATIONORDERING INFORMATIONSYSTEM DESIGN
Variable speed
Fixed speed
Fixed speedVariable speedTandem model Suction direction
DSH090VZH088V ZH178HLeft/Right
DSH120VZH088VZH208HLeft/Right
DSH140VZH117VZH257HLeft/Right
DSH161VZ H117VZH278HLeft/Right
DSH184V ZH117VZH301HLeft/Right50 & 60120Z0656
DSH184VZH170VZH354H
DSH240V ZH170VZH410HLeft/Right50 & 60120Z0657
DSH295V ZH170VZH465HLeft/Right50 & 60120Z0655
Note:
The tandem accessory includes oil equalization kits and oil level sensor. For compressors that need a UL certificate, please order the accessory kit with the 24V oil level sensor.
+
+
+
+
+
Left
+
Right
+
+
+
Hz of FS
compressor
50120Z0 676
6012 0Z0675
50120Z0664
60120Z0658
50120Z0666
60120Z0665
50120Z0665
60120Z 0674
50
60
50
60
Fixed speed
Suction
separator code
120Z0683
120Z0683
120Z0655
120Z0655
120Z0 687
120Z0 687
120Z0 687
120Z0 687
Variable speed
Tandem accessory kit code
120Z0653 (with 24V oil level sensor)
120Z0654 (with 230V oil level sensor)
120Z0653 (with 24V oil level sensor)
120Z0654 (with 230V oil level sensor)
120Z0651 (with 24V oil level sensor)
120Z0652 (with 230V oil level sensor)
120Z0651 (with 24V oil level sensor)
120Z0652 (with 230V oil level sensor)
120Z0653 (with 24V oil level sensor)
120Z0654 (with 230V oil level sensor)
120Z0653 (with 24V oil level sensor)
120Z0654 (with 230V oil level sensor)
120Z0653 (with 24V oil level sensor)
120Z0654 (with 230V oil level sensor)
120Z0653 (with 24V oil level sensor)
120Z0654 (with 230V oil level sensor)
120Z0651 (with 24V oil level sensor)
120Z0652 (with 230V oil level sensor)
120Z0682 (with 24V oil level sensor)
120Z0681 (with 230V oil level sensor)
120Z0682 (with 24V oil level sensor)
120Z0681 (with 230V oil level sensor)
120Z0682 (with 24V oil level sensor)
120Z0681 (with 230V oil level sensor)
120Z0682 (with 24V oil level sensor)
120Z0681 (with 230V oil level sensor)
120Z0649 (with 24V oil level sensor)
120Z0650 (with 230V oil level sensor)
120Z0649 (with 24V oil level sensor)
120Z0650 (with 230V oil level sensor)
+
10AB298632269085en-000401
Design pipe
Suction separator
Oil equalization design
The suction connections of the two individual
compressors are interconnected by a suction
separator, which is supplied as an accessory.
The two compressors are connected by a ½" or
¾" oil equalization pipe. To fix the oil equalization
connection rotolock, use the adaptor sleeves
½"
Suction separator
and the seal gasket which were included in the
tandem accessory kit.
Supplied with the compressor
Included in tandem kit
Not supplied
Supplied with the compressor
Included in tandem kit
Not supplied
11AB298632269085en-000401
Design compressor mounting
Tightening torque
General requirements
VZH178H Mounting feet
GENERAL INFORMATIONPRODUCT INFORMATIONORDERING INFORMATIONSYSTEM DESIGN
VZH208H Mounting feet
The tandem is fixed to the frame using the
flexible grommets that are supplied with
The compressors are fixed to the frame using
rubber grommets, mounting sleeves, and
washers (supplied with the compressors).
HM 8 bolt
Lock washer
Flat washer
Steel mounting
sleeve
Rubber grommet
Nut
Base plate, frame, etc. with sucient rigidity
Mounting for DSH090 and VZH088
15Nm
15 mm
The compressors are fixed to the frame using
rubber grommets, mounting sleeves, and
washers (supplied with the compressors).
Because VZH088 is 7 mm smaller than DSH120,
in order to ensure that the oil equalization
Tightening torque
HM 8 bolt
Lock washer
Flat washer
Steel mounting
sleeve
Rubber grommet
15Nm
15 mm
the compressor or which are included in the
accessory kit.
connection is at the same level for both
compressors, an additional 7mm rigid spacer
must be added under VZH088 (see drawing. The
7 mm rigid spacer is supplied with the tandem
accessory kit).
Tightening torque
15Nm
Rigid spacer
VZH257H / VZH278H
Mounting feet
Nut
Base plate, frame, etc. with sucient rigidity
Mounting for DSH120
The compressors are fixed to the frame using
rubber grommets, mounting sleeves, and
washers (supplied with the compressors).
Tightening torque
HM 8 bolt
Lock washer
Flat washer
Steel mounting
sleeve
Rubber grommet
Nut
Base plate, frame, etc. with sucient rigidity
Mounting feet
15Nm
15 mm
Mounting for VZH088
12AB298632269085en-000401
Design compressor mounting
Tighteningtorque 21Nm
28mm
HM8 bolt
VZH301H Mounting feet
VZH410H / VZH465H
Mounting feet
The compressors are fixed to the frame using
rubber grommets, mounting sleeves, and
washers (supplied with the compressors).
Because VZH117 is 7 mm smaller than DSH184,
in order to ensure that the oil equalization
Tightening torque
HM 8 bolt
Lock washer
Flat washer
Steel mounting
sleeve
Rubber grommet
Nut
Base plate, frame, etc. with sucient rigidity
Mounting for DSH184
15Nm
15 mm
The compressors are fixed to the frame using
rubber grommets, mounting sleeves, and
washers. The VZH mounting kits are supplied
connection is at the same level for both
compressors, an additional 7mm rigid spacer
must be added under VZH117 (see drawing. The
7 mm rigid spacer is supplied with the tandem
accessory kit).
Tightening torque
15Nm
GENERAL INFORMATIONPRODUCT INFORMATIONORDERING INFORMATIONSYSTEM DESIGN
Rigid spacer
Mounting for VZH117
with the VZH compressor, and DSH mounting kits
are included in the tandem accessory kit.
VZH354H Mounting kit
Tightening
HM 8 bolt
Lock washer
Flat washer
Steel mounting sleeve
Rubber grommet
Nut
Mounting feet
torque 21Nm
Compressor
base plate
28 mm
The compressors are fixed on the frame using
rubber grommets, mounting sleeves, washers
(delivered with the compressors).
Tightening
torque 15Nm
Lock washer
Steel mounting
sleeve
Nut
HM8 bolt
Flat
washer
Rubber
grommet
Rigid
spacers
Because DSH184 is 14mm smaller than VZH170,
in order to have oil equalization connection at the
same level for both compressors, two additional
7mm rigid spacers must be added under DSH184
(See below drawing, two 7mm rigid spacers are
provided in Tandem accessory kit).
HM8 bolt
Tightening
torque 21Nm
28mm
Base plate, frame, etc. with enough rigidity
Mounting for DSH184Mounting for VZH170
13AB298632269085en-000401
Design oil level sensor
General requirementsOil level sensor is a special component which
assembles on variable speed compressor. It is
GENERAL INFORMATIONPRODUCT INFORMATIONSYSTEM DESIGNORDERING INFORMATION
GENERAL INFORMATION
VZH088VZH117VZH170
provided in oil level sensor accessory kit.
14AB298632269085en-000401
Manage operating envelope
RequirementThe operating envelope for hybrid manifolding is
shown below, and guarantees reliable operation
of the compressor for steady-state operation.
VZH088/117 C Operating Map - 575V/400V/208V
75
70
65
60
55
50
45
40
Tc (°C)
35
30
25
20
15
10
5
-35-30-25-20-15-10-505151030352520
50-90 rps
50-100 rps
30-90 rps
The steady-state operation envelope is valid for a
suction superheat of between 5K and 30K.
30-90 rps
GENERAL INFORMATIONPRODUCT INFORMATIONSYSTEM DESIGNORDERING INFORMATION
25-90 rps
25-100 rps
Te (°C)
VZH170 C Operating Map - 575V/400V/208V
75
70
65
60
55
50
45
40
Tc (°C)
35
30
25
20
15
10
5
-35-30-25-2 0-15-10-505151030352520
50-90 rps
50-100 rps
25-100 rps
30-90 rps
30-90 rps
25-90 rps
Te (°C)
Note:
1) The solid line envelope is valid for a suction superheat within 5K (9°F) at nominal voltage. Higher suction superheat may lead to
discharge temperatures above 135°C (275°F)
For superheat between 5K and 11K, this top left envelope might be reduced by condensing temperature of 1°C or 2°C (1. 6°F to
3.2°F) in order to keep discharge T° below 135°C (275°F)
For superheat above 11K (20°F), the envelop will further be reduced based on 135°C (275°F) discharge temperature restriction.
2) For 380V power input, permitted highest condensing temperature will decrease accordingly: 25-100rps, condensing temperature
from 60°C to 56°C(140°F to 133°F); 30-90rps, condensing temperature from 68°C to 65°C(154°F to 149°F).
SYSTEM DESIGN
Pressure settings
bar (g)psi (g)
R410A
Working pressure range low side2. 3~15. 733.36~227.7
Maximum high pressure safety switch setting48.7706.33
Minimum low pressure safety switch setting1.521.75
GENERAL INFORMATIONPRODUCT INFORMATIONSYSTEM DESIGNORDERING INFORMATIONGENERAL INFORMATION
Speed limit guarantees compressor
reliability and must be respect. Details refer to
single VZH M/L GEN3 guideline”Manage speed
limit”
16AB298632269085en-000401
Manage superheat
Requirement
System evaluation
Basic unit
single exchanger
as evaporator and
condenser
XXOptionalPass liquid flood back test
X-XRecommended
During normal operation, refrigerant enters the
compressor as a superheated vapour. Liquid
flood back occurs when some of the refrigerant
entering the compressor is still in a liquid state.
In the steady-state condition, the expansion
device must ensure a suction superheat of
between 5k and 30k.
Advance unit
Multiple exchangers as evaporator or
condenser (heat-recovery, exchanger,
four-pipe chiller…)
XXMandatoryPass liquid flood back test
XXMandatory
Liquid flood back can cause oil dilution and, in
extreme situations, lead to liquid slugging that
can damage compression parts.
GENERAL INFORMATIONPRODUCT INFORMATIONORDERING INFORMATION
Tes t
Non-reversible
Reversible
Suction accumulator
Pass liquid flood back test
Pass defrost test
Pass liquid flood back test
Pass defrost test
Test, criteria and solutions
Tes t NoPurposeTest conditionPass criteriaSolutions
Liquid flood back testing must be
carried out under expansion valve
threshold operating conditions:
Variable speed On at min.speed /
fixed speed Off
Running conditions corresponding
to the lowest foreseeable
evaporation, and highest
foreseeable condensation
In case of reversible system, the test
must be done in both cooling and
heating mode
If advanced unit, test in all possible
configurations
Tests must be carried out in the
most unfavourable conditions:
• fan staging
• compressor ramping up and down
The defrost test must be carried out
in the most unfavorable conditions
(at 0°C evaporating temperature)
Suction superheat >5k
The oil superheat must not be more
than 30 sec below the safe limit
defined in the dilution chart (see
graph below)
The oil superheat must not be more
than 30 sec below the safe limit
defined in the dilution chart (see
graph below)
1. Check expansion valve selection
and setting
(EXV) check measurement chain and
PID.
2. Add a suction accumulator*
1. In reversible systems, the defrost
logic can be worked out to limit the
liquid flood back effect. (For more
details see “Control logic”)
2. Add a suction accumulator*
Liquid flood
back test
Defrost test
Steady-state
Trans ient
Check liquid
flood back
during defrost
cycle
SYSTEM DESIGN
* A suction accumulator offers protection by trapping the liquid refrigerant upstream from the compressor. The accumulator should be
sized at least 50% of the total system charge. The suction accumulator dimensions can impact oil return (gas velocity, oil return, hole size
etc.), and therefore the oil return has to be checked according to the “Manage oil in the circuit” section.
17AB298632269085en-000401
Manage superheat
GENERAL INFORMATIONPRODUCT INFORMATIONORDERING INFORMATION
The oil temperature sensor
must be placed between the oil
sight glass and the compressor
baseplate for fixed speed
compressor, and beside the oil
level sensor for the variable speed
compressor.
Use a little thermal paste to
improve conductivity. The sensor
must also be thermally insulated
correctly from the ambience.
Oil superheat is defined as:
(Oil temperature - Evaporating temperature)
VZH088 117 170/R410A
SYSTEM DESIGN
Dilution chart (reference at 20°C / 68°F ambient temperature)
15
14
13
12
Safety area
11
10
9
8
7
6
5
Oil superheat (K)
4
3
Unsafety area Max 60secs per event
2
1
0
-25
-20-15-100510152025
Saturated Suction temperature °C
18AB298632269085en-000401
Manage off-cycle migration
Off-cycle refrigerant migration happens:
• when the compressor is located at the coldest
part of the installation, and refrigerant vapour
then condenses in the compressor, or
Requirement
The amount of liquid refrigerant in the
compressors must not exceed the charge limit.
System evaluation
Non splitSplitBelow charge limitAbove charge limit
XXOptionalMandatoryMandatoryOptional
XXMandatoryMandatoryMandatoryRecommended
X--MandatoryMandatoryMandatoryRecommended
*Surface sump heater
The surface sump heaters are designed to
protect the compressor against off-cycle
refrigerant migration.
Additional heater power or thermal insulation
is needed in case the ambient temperature falls
below -5°C and the wind speed is above 5 m/sec.
The heater must be turned on whenever all the
compressors are off.
Surface sump heater accessories are available
from Danfoss (see the “Accessories” section).
Surface sump
heater*
• directly in the liquid phase as the result of
gravity. When the compressor starts running
again, the refrigerant diluted in the oil generates
poor lubrication conditions. In extreme
situations, this leads to liquid slugging that can
damage compressor parts.
Non-return valve
Liquid line
solenoid valve**
Pump-down
cycle***
**Liquid line solenoid valve (LLSV)
An LLSV is used to isolate the liquid charge
on the condenser side, thereby preventing
refrigerant being transferred to the compressor
during off-cycles. The electronic expansion valve
that closes automatically including in power
shut down situation can replace the LLSV. The
quantity of refrigerant on the low-pressure side
of the system can be further reduced by using a
pump-down cycle in association with the LLSV.
***Pump-down cycle
By decreasing pressure in the sump, pump down:
• evacuates refrigerant from the oil
• sets the sump saturating pressure much lower
than the ambient temperature, and as a result,
refrigerant condensation is avoided in the
compressor.
Pump-down switch setting must be set higher
than 2.3 bar(g).
GENERAL INFORMATIONPRODUCT INFORMATIONORDERING INFORMATION
SYSTEM DESIGN
Refrigerant charge limit
table
For more details on pump-down cycle see the
section “Control logic”.
Tandem modelsRefrigerant charge limit(kg)
VZH178H/VZH208H8.0
VZH257H/VZH278H/VZH301H10.0
VZH354H/VZH410H/VZH465H15. 0
19AB298632269085en-000401
Manage oil in the circuit
Non return valve
GENERAL INFORMATIONPRODUCT INFORMATIONORDERING INFORMATION
Oil management system
for hybrid manifolding
Non-return valve at discharge prevents
R
from liquid or gas migration. Selection of nonreturn valve is a trade-off between pressure
dropping at high speed, and the state of the
valve stability while at low speed.
See Section Prevent off cycle migration §Test and
components required per application to know
when to use non return valve
The oil management system architecture for
hybrid manifolding is described below.
An oil equalization tube between the variable
speed compressor and the fixed speed
compressor is used to maintain the oil balance.
OEM main controllerDrive
ModBus
The following table displays present Danfoss
non-return valve selection per each specific
compressor. DSH are with internal NRV, no need
external NRV.
Compressor modelNRV model
VZH088NRV 16
VZH117NRV 19
VZH170NRV 22
An oil level sensor need to be installed on the
variable speed compressor. The oil level sensor
monitors the compressor oil level and send oil
level signal to OEM main controller. When oil
level is below the minimal, OEM controller enter
in oil management mode to recover a proper
oil level in compressor. If oil level cannot be
recovered, controller stop the system.
SYSTEM DESIGN
Oil management logic
FS
Power supply
Oil equalization tube
In order to maintain the proper oil level in the
compressors, an oil management control logic
needs be implemented in the OEM controller.
The oil management control logic must include
three steps.
1. In the case of low oil level detection, an oil
balance mode (Variable speed on, Fixed speed
off) is activated to recover oil from fixed speed
to variable speed.
VS
Optical oil
level sensor
2. If oil level cannot be recovered in VS
compressor, controller go to Oil boost Mode
(Variable speed on, Fix Speed on) in order to
recover oil trapped in system.
3. If the oil level is still below the limit after a full
oil balance action and oil boost action have
been completed, the controller must enter in
protection mode, and stop the system in alarm.
For more detailed oil management logic, please
refer to “Oil management logic” in the annex.
20AB298632269085en-000401
Manage oil in the circuit
Requirement
Fixed speed compressor: The oil level must
be visible or full in the sight glass when the
compressor is running and when all the
compressors in the circuit are stopped.
Variable speed compressor: This compressor is
equipped with an oil level switch located at the
minimum acceptable level. If the oil level drops
below this limit, the controller must follow the oil
logic (See “Oil management logic” in the annex).
R
Fixed speed compressor oil returned status
need be monitored in qualification test by
normal OSG on FS compressor or additional oil
level switch placed on FS OSG, the OEM should
make sure enough oil in FS compressor by test on
their own unit.
System evaluation
Basic unit
Single exchanger
as evaporator and
condenser
X--XOptionalPass tests 1 & 2
-----XMandatoryPass tests 1, 2 & 3
Advance unit
Multiple exchangers as
evaporator or condenser
(heat-recovery, exchanger,
four-pipe chiller…)
X--XRecommendedPass tests 1 & 2
Split
Non-reversible
Reversible
Non-split
Oil separator
Test, criteria and solutions
Tes t no.PurposeTest conditionPass criteriaSolutions
Variable speed On at minimum
speed / Fixed speed Off
Running condition corresponds to
lowest foreseeable evaporation,
and highest foreseeable
condensation on the system
Running for 6 hours
For a reversible system, perform
the test in both heating and cooling
Oil return
1
2
3
test under
minimum mass
flow
Check oil
management
control logic is
working
Oil return in
split system
modes. If it is an advanced unit, test
in all possible configurations
Variable speed On at minimum
speed / Fixed speed On
Running condition corresponding
to lowest foreseeable evaporation,
and highest foreseeable
condensation on the system
Running for 6 hours
For a reversible system, perform
the test in both heating and cooling
modes. If it is an advanced unit, test
in all possible configurations
Variable speed On at 50 rps for
VZH088-117 or 40 rps for VZH170 /
Fixed speed On
Running conditions corresponding
to the lowest foreseeable
evaporation, and the highest
foreseeable condensation on the
system.
Running for 6 hours
For a reversible system, perform
the test in both heating and cooling
modes. If it is an advanced unit, test
in all possible configurations
Since each installation is unique,
tests 1 and 2 cannot fully validate
the oil return
The oil level must be checked and
adjusted at commissioning
Variable speed: No lack of oil alarm
No more than two oil boost cycles
per hour
Variable speed: No lack of oil alarm
Fixed speed: Oil visible in sight glass
No more than two oil balance cycles
per hour
Fixed speed: Oil visible in sight glass
Fix speed: Oil visible in sight glass
No more than two oil balance cycles
per hour
Look for potential oil trap
Increase oil boost duration
Top up with oil, generally 4% of the
total system refrigerant charge (in
weight)
Oil separator can be added
Look for potential oil trap
Increase oil boost duration
Top up with oil, generally 4% of the
total system refrigerant charge (in
weight). If more than 4% is used,
look for a potential oil trap in the
system
Oil separator can be added
The oil separator is mandatory
Pay special attention to “Piping
design”
Top-up with oil, generally 4% of the
total system refrigerant charge (in
weight). If more than 4% is used,
look for a potential oil trap in the
system
GENERAL INFORMATIONPRODUCT INFORMATIONORDERING INFORMATION
Tes t
SYSTEM DESIGN
21AB298632269085en-000401
Control logic
Safety control logic
requirements
Safeties
HP switch
LP safety switch
GENERAL INFORMATIONPRODUCT INFORMATIONORDERING INFORMATION
Electronic module (only for
SH180-240 -295)
See the pressure settings
table in the “Manage
operating envelope section”
Contact M1-M2 opened
Short cycle protectionMinimum run time is necessary to ensure proper
oil return to the compressor. A 3 minutes
minimum run time is usually recommended but
some systems may require more time to establish
a proper superheat and a stable oil return.
Additionally, compressor must not exceed a
maximum of 12 starts per hour. 12 starts per
Tripping conditionsRe-start conditions
ValueTimeValueTime
Manual reset
Immediate, no delay
No by-pass
Conditions back to normal
Switch closed again
Max. 5 auto resets during a
12-hour period, then manual
reset
Max. 5 auto resets during a
12-hour period, then manual
reset
is the maximum number of starts acceptable for
a limited period to ensure enough time for oil
return after start-up.
Short cycle protection can be done either by the
drive or the unit controller. The following table
describes the parameters to adjust depending on
short cycle protection selected
hour must not be considered as an average, this
Drive parametersDescriptionValueDefault
Short cycle protection is done by unit controller
28.00Short cycle protection
Short cycle protection is done in drive; LP (low pressure) protection must be connected to T27 to keep LP protection during minimum running time.
Terminal 27 (Par 5.12) must be set to “Coast inverse”
If Modbus is used it is not necessary to connect terminal 27, but a “Coasting” command must be sent to be able to stop compressor in case of an alarm
during minimum run time
Short cycle protection done in unit controller: (preferred
option)
DisableEnable
28.00Short cycle protectionShort cycle protection done by the drive.EnableEnable
28.01Interval between starts
28.02Minimum Run time
SYSTEM DESIGN
5.12Terminal 27 Digital inputDesignated for the LP switch.
The diagram below demonstrates how the function works:
(a) Start signal is given by the unit controller
(b) Compressor started
(c) Compressor stop requested by the unit controller
(d) Stop command is ignored. Stop delay warning (W97).
(e) Compressor stops when minimum run time (180s) has
elapsed.
(f) Start signal is given by the unit controller
Start command is ignored until the timer (300s) has
elapsed. Only then, can the compressor start.
The compressor cannot stop until the set time (180s) has
elapsed.
The timer starts counting following a compressor start.
Stop command is ignored.
Only a coast (inverse) command can override the time
and stop the compressor.
Interval between starts 300sec
(g) Start delay (W96)
(b) Compressor started
(c) Stop signal
(d) Stop delayed (W97)
(e) Compressor Stoped
300 sec300sec
180 sec12se c
[2]* Coast
inverse
(h) Compressor start
(g) Start command is ignored
(h) Compressor starts after the timer interval between starts
(300s) has elapsed.
(i) Compressor Coast (stop) This command can override
the time minimum run time and stop the compressor
immediately.
(a) Start signal
Note:
The short cycle protection function is not functional during Hand On control of the
frequency converter via the LCP. If selecting Hand On or Off, the two timers will be reset to
0, and not start counting until Auto is pressed and an active start command applied. The
counters are not available for display or monitoring.
(f) Star t signal(i) Compressor Coast
Stop inverse
22AB298632269085en-000401
Control logic
Defrost logic
recommendations
Variable speed 1
Fixed speed 2
4WV
EXV
ON
ON
Heating
100%
In reversible systems, the defrost logic can be
worked out to limit the effects of liquid flood
back by:
1. Running at full load during defrost to share the
liquid refrigerant between all the compressors.
The following defrost logic combines both
advantages:
Defrost
2. Transferring the liquid refrigerant from one
exchanger to the other thanks to pressures.
GENERAL INFORMATIONPRODUCT INFORMATIONORDERING INFORMATION
Pump-down logic
recommendations
4 Way Valve (4WV) stays in heating mode.
Defrost start. Stop all compressors
EXV opens to transfer liquid from outdoor
to indoor exchanger thanks to pressure
difference
* EXV opening degree and time have to be set to keep a minimum pressure for 4 way valve moving.
Pump down is initiated prior to shutting
down the last compressor on the circuit by
de-energizing a liquid line solenoid valve or
closing electronic expansion valve. When suction
pressure reaches the cut-out pressure, the
compressor is stopped.
When the pressures are almost bal-
anced*, 4WV changes to cooling mode
Restart variable speed and fixed speed
Defrost end. Stop all compressors
4 WV stays in cooling mode.
EXV opens to transfer liquid from
indoor to outdoor exchanger thanks
to pressure difference
When pressures are almost balanced*,
change 4WV to heating mode.
Restart variable speed and fixed speed
Two types of pump-down exist:
• One-shot pump down (preferred): When the
last compressor in the circuit stops, the suction
presssure is falls by 1.5 bar below the nominal
evaporating pressure with a minimum of 2,3
bar(g). Even if the suction pressure increases
again, the compressor will not restart.
• Continuous pump-down: Compressor restarts
automatically when the suction pressure
increases.
SYSTEM DESIGN
23AB298632269085en-000401
Assembly line procedure
The installation and service procedure for a
parallel system are similar to basic single-system
installations. The selection of additional system
components for parallel installations follows the
HandlingDanfoss Commercial Compressors recommends
using the lift and handling devices as shown on
the right, and that the following procedure be
used to prevent damage:
• There are two lifting rings on each compressor.
GENERAL INFORMATIONPRODUCT INFORMATIONORDERING INFORMATION
Use all four rings.
• Maximum loads authorized per sling and for the
hoist hook must not be lower than the weight
of the assembly.
• If the tandem unit is already installed as a
complete installation, it must never be lifted
using the lifting rings on the compressors.
basic system common rules. Please refer to the
application guidelines for Danfoss VZH Gen3
scroll compressors (AB300034185311en) for
detailed installation and service procedures.
SYSTEM DESIGN
24AB298632269085en-000401
Ordering information
To build a complete tandem installation,
the customer must order two must order 2
Compressor ordering
codes
Danfoss VZH and DSH scroll compressors can
be ordered in either industrial packs or in single
packs. Please refer to the single compressor
Accessory ordering codes
The suction separator and tandem kit can
be ordered using the code numbers listed in
the table below. The suction separator and
Tandem model
VZH178 HVZH088DSH090Left/Right
VZH208HVZH088DSH120Left/Right
VZH257HVZH117DSH140Left/Right
VZH278HVZH117DSH161Left/Right
VZH301HV ZH117DSH184Left/Right
VZH354HVZ H170DSH184
VZ H410HVZH170DSH240Left/Right
VZH465HVZH170DSH295Left/Right
Variable speed
compressor
Fixed speed
compressor
Suction
direction
Left
Right
Suction separatorTandem accessory kit
Hz (FS
compressor)
50 Hz120Z06761
60 Hz120Z06751
50 Hz120Z06641
60 Hz120Z06581
50 Hz120Z06661
60 Hz120Z06651
50 Hz120Z06651
60 Hz120Z06741
50 Hz120Z06561
60 Hz120Z06561
50 Hz
60 Hz120Z06551
50 Hz120Z 068 71
60 Hz120Z 06871
50 Hz120Z06571
60 Hz120Z06571
50 Hz120Z06551
60 Hz120Z06551
CodePack size
120Z0683
compressors, one suction separator and one
tandem accessory kit.
application guideline for compressor ordering
information (AB300034185311en for VZH Gen3,
AB288965961751en for DSH).
the tandem kit selection should be based on
compressor model, frequency of fixed speed
compressor and oil level switch voltage.
Voltage of oil
level switch
24V120Z06531
230V120Z06541
24V120Z06531
230V120Z06541
24V120Z06511
230V120Z06521
24V120Z06511
230V120Z06521
24V120Z06531
230V120Z06541
24V120Z06531
230V120Z06541
24V120Z06531
230V120Z06541
24V120Z06531
230V120Z06541
24V120Z06511
230V120Z06521
24V120Z06511
230V120Z06521
1
24V120Z0 6821
230V120Z06811
24V120Z0 6821
230V120Z06811
24V120Z0 6821
230V120Z06811
24V120Z0 6821
230V120Z06811
24V120Z0 6491
230V120Z06501
24V120Z0 6491
230V120Z06501
24V120Z0 6491
230V120Z06501
24V120Z0 6491
230V120Z06501
CodePack size
GENERAL INFORMATIONPRODUCT INFORMATIONSYSTEM DESIGN
120Z0 388 Surface sump heater, 80W, 24V, CE, UL
120Z0 389 Surface sump heater, 80W, 230V, CE, UL Multipack8
120Z0 390 Surface sump heater, 80W, 400V, CE, UL Multipack8
120Z0 391 Surface sump heater, 80W, 460V,CE, UL Multipack8
120Z0 402 Surface sump heater, 80W, 575V, CE, UL Multipack8
120Z0 360 Surface sump heater + bottom insulation, 56 W, 24 V, CE, UL
120Z0 376 Surface sump heater + bottom insulation, 56 W, 230 V, CE, UL Multipack6
120Z0 377 Surface sump heater + bottom insulation, 56 W, 400 V, CE, UL Multipack6
120Z0378 Surface sump heater + bottom insulation, 56 W, 460 V, CE, UL Multipack6
120Z0 379Surface sump heater + bottom insulation, 56 W, 575 V, CE, ULMultipack6
120Z0 66748W 24V surface sump heater CE and UL
120Z0 66848W 230V surface sump heater CE and ULSingle pack1
120Z066948W 400V surface sump heater CE and ULSingle pack1
120Z0 67048W 460V surface sump heater CE and ULSingle pack1
120Z0 67148W 575V surface sump heater CE and ULSingle pack1
120Z0 38880W 24V surface sump heater CE and ULMultipack8
120Z0 38980W 230V surface sump heater CE and ULMultipack8
120Z0 39080W 400V surface sump heater CE and ULMultipack8
120Z0 39180W 460V surface sump heater CE and ULMultipack8
120Z0 40280W 575V surface sump heater CE and ULMultipack8
120Z070 356W 24V surface sump heater + bottom insulation, CE & ULDSH240-295-381-485Multipack6
120Z070 456W 230V surface sump heater + bottom insulation, CE & ULDSH240-295-381-485Multipack6
120Z070 556W 400V surface sump heater + bottom insulation, CE & ULDSH240-295-381-485Multipack6
120Z070 656W 460V surface sump heater + bottom insulation, CE & ULDSH240-295-381-485Multipack6
120Z070756W 575V surface sump heater + bottom insulation, CE & ULDSH240-295-381-485Multipack6
VZH088-117
VZH170
DSH090 to 184
Multipack8
Multipack6
Single pack1
GENERAL INFORMATIONPRODUCT INFORMATIONSYSTEM DESIGN
ModelConfigration NRV code
VZH178 HVZH088 + DSH090
VZH208HVZH088 + DSH120
VZH257HVZH117 + DSH140
VZH278HVZH117 + DSH161
VZH301HVZH117 + DSH184
VZH354HVZH170 + DSH184
VZ H410HVZH170 + DSH240
VZH465HVZH170 + DSH295
VZH088DSH090
NRV16 (020B1059)-
VZH088DSH120
NRV16 (020B1059)-
VZH117DSH140
NRV19(020 B1054)-
VZH117DSH161
NRV19(020 B1054)-
VZH117DSH184
NRV19(020 B1054)-
VZH170DSH184
NRV22 (020 -1060)-
VZH170DSH240
NRV22 (020 -1060)-
VZH170DSH295
NRV22 (020 -1060)-
ORDERING INFORMATION
27AB298632269085en-000401
Annex
Oil Management logic
1. Oil management for
hybrid manifolding
system
An oil level sensor needs to be installed on
the variable speed compressor. The oil level is
permanently monitored by OEM main controller.
When oil level is below the minimal, OEM
OEM main controllerDrive
ModBus
FS
controller enters in oil management mode to
recover a proper oil level in compressor. If oil level
cannot be recovered, controller stops the system.
VS
2. Oil management
description
2.1 Basic rules
Power supply
Oil equalization tube
Oil management system for hybrid manifolding
This specification describes the control logic to
implement in OEM controller. This control logic
must be implemented and thoroughly tested by
OEM.
The variable speed compressor (VS) is primary
and the fixed speed compressor (FS) is Secondary.
FS must not run alone.
Optical oil
level sensor
As oil balancing logic needs to start / stop
compressor as well as increase / decrease speed,
make sure expansion device is fast enough to
maintain liquid flood back within acceptable
limit during those transients (Manage super heat
chapter).
28AB298632269085en-000401
Annex
2S
2.2 Oil management modes
The oil management control logic must include
3 steps.
Less than every
20min (TD2*)
Max 45 sec
(TD1*)
Fix speed ON
Oil
balance
Fix speed OFF
Partial Oil
boos (VS only)
Step 1Step
Normal
operation
Low oil level
>5 sec
Low oil
level
Step 1 (Oil balance or partial oil boost)
In case of low oil level detection by Oil level
sensor on VS, there is 2 possible actions
according to fix speed state:
• Fix speed is ON: Oil can be trapped in fix speed
compressor due to pressure unbalance. Oil
balance mode is activated. FS is stopped and
VS speed is increased; pressure in VS become
lower than FS oil is coming back through oil
equalization line.
• Fix speed is OFF: Oil is trapped in the system.
Partial oil boost is activated. VS speed is
increased to slightly increase refrigerant velocity
in the system and recover oil, FS remain OFF
Less than every
45min (TD4*)
Max 5min
(TD3*)
Oil level
not
recovered
Oil
Boost
(FS + VS)
Oil level
not
recovered
than TD2 after last step 1, switch immediately to
step 2.
Step 2 (Full oil boost)
If oil level cannot be recovered within defined
time, oil is trapped in the system. Full oil boost
is activated. (VS speed is increased and fix starts
(if not already ON). It considerably increases
refrigerant velocity in the system and recovers oil.
TD3 is the maximum time to complete step 2. If
oil is not recovered within TD3 switch to step 3. If
oil is recovered within TD3 come back to normal
operation. TD4 is the minimum interval between
two step 2. In case of low oil level detection
within a time <TD4, switch to step 3.
Protection
tep 3
TD1 is the maximum time to complete
Step 1: If oil is not recovered within TD1, switch to
Step 2: If oil is recovered within TD1 come back to
normal operation. TD2 is the minimum interval
between two step 1. If step 1 is requested in less
Step 3 (Protection)
If oil is still lower than limit after completed step
1 & 2, or if oil level drop within a time <TD4,
controller must enter in protection mode, and
stop the system in alarm.
Note: TD time is adjustable. Please refer to “Parameter and variable table” in page 31.
29AB298632269085en-000401
Annex
2.3 Steps description
2.3.1 Oil balanceFunction description
Balance oil from FS compressor to VS Compressor.
Enter condition
Low oil level in VS compressor detected by oil
level sensor.
AND
FS compressor is ON
AND
t2>TD2, Interval between two Oil balance / Oil
boost is > TD2
Cancel condition
High oil level in VS compressor detected by oil
level sensor.
OR
t1>TD1, Oil balance duration exceed TD1
Control sequence
1. At the initial state, VS and FS compressor are
ON.
2. Low oil level detected in VS compressor. Reset
and Start t1.
3. FS compressor must stop. VS compressor speed
must increase to Fboost.
4. When high oil level detected in VS compressor.
• VS compressor speed must be decreased to
minimal speed Fmin.
• Reset and Start t2
• Reset t1
5 When VS compressor speed reaches FStart, FS
compressor must restart.
Max TD1
Oil level signal
VS speed
FS speed
t1
Oil lack
2
Fboost
1
3
Oil balance
from FS to VS
compressor
4
t2
FstartFstart
5
30AB298632269085en-000401
2.3.2 Partial oil boostFunction description
Return oil trapped in the system to compressors
by increasing refrigerant mass-flow in the system.
Enter condition
Low oil level in VS compressor detected by oil
level sensor.
AND
FS compressor is OFF
AND
t2>TD2, Interval between two Oil balance / Oil
boost is > TD2
Cancel condition
High oil level in VS compressor detected by oil
level sensor.
OR
t1>TD1,Partial oil Boost duration exceed TD1
Oil level signal
Control sequence
1 At the initial state, VS compressor is ON and FS
compressor is OFF.
2 Low oil level detected in VS compressor. Reset
and start t1
3 VS compressor speed must increase to Fboost.
4 When high oil level detected in VS compressor
• VS compressor speed must be decreased to the
initial speed (Fstart)
• Reset and start t2
• Reset t1
Max TD1
t1
Oil lack
t2
VS speed
FS speed
2
1
3
Fboost
4
31AB298632269085en-000401
Annex
2.3.3 Oil boostFunction description
Return oil trapped in the system to compressors
by increasing refrigerant mass-flow in the system.
Enter condition
Low oil level in VS compressor detected by oil
level sensor.
AND
(t1>TD1, Oil balance / boost duration t1 > TD1 OR
t2<TD2, Interval between two Oil balance / Oil
boost is < TD2)
Cancel condition
High oil level in VS compressor detected by oil
level sensor.
OR
t1>TD3, Oil balance / boost duration exceeds
Maximum Oil boost duration
Control sequence
1. At initial state, oil level is low .Partial oil boost
/Oil balance was not successful or was aborted
because minim interval criteria. VS compressor is
at FStart and FS compressor is either ON or OFF.
2. VS compressor speed must increase to Fboost,
FS compressor must start if not already ON
Reset and start t1
3. When High oil level detected in VS compressor.
• VS compressor speed must be decreased to the
initial speed (Fstart)
• FS compressor to initial state.
• Reset and start t2
• Reset and start t3
• Reset t1
4. When VS compressor speed reaches FStart, FS
compressor must restart (if was ON before)
Max TD3
t1
2
Oil lack
t2
VS comp
FS comp
1
Fboost
3
FstartFstart
32AB298632269085en-000401
Annex
24VDC MODEL
24VAC MODEL
24VDC MODEL
2.3.4 Protection
Function description
Stop compressors to prevent short of oil running.
Enter condition
Low oil level in VS compressor detected by oil
level sensor.
AND
(t1>TD3, Oil balance / boost duration exceeds
Cancel condition
Manual Reset
Control sequence
Stop FS and VS compressor
Reset t1
Reset t2
Reset t3
TD3 OR t3<TD4, Interval between two Oil boost
is < TD4)
t2Interval between two oil balance / Partial oil boostVariableminutes
t3Interval between two oil boostVariableminutes
2.5 Sensor Wiring diagram
230VAC MODEL
24VAC MODEL
An TEKLAB LC-XN optical-electrical level sensor
is fixed on the inverter compressor. The oil
level sensor monitors the compressor oil level
and sends oil level signal to an external relay
(provided by OEM ). Regarding this oil level
signal, a 5±2 seconds delay is recommended to
flowing through load or coil of external relay.
For relay, output is open.
- Enough oil: Circuit between 2 and 3 will be
closed internally, there will be current flowing
through load or coil of external relay. For relay,
output is closed
24VDC MODEL
be used to consider the oil level fluctuation which
may trigger false alarms.
For customers who needs UL certificates, please
order 24V AC/DC sensor.
- Lack of oil: Circuit between 2 and 3 will be
opened internally, there will be no current
33AB298632269085en-000401
Danfoss Commercial Compressors
Danfoss Inverter Scrolls
is a worldwide manufacturer of compressors and condensing units for refrigeration and HVAC applications. With a wide range
of high quality and innovative products we help your company to find the best possible energy efficient solution that respects
the environment and reduces total life cycle costs.
We have 40 years of experience within the development of hermetic compressors which has brought us amongst the global
leaders in our business, and positioned us as distinct variable speed technology specialists. Today we operate from engineering
and manufacturing facilities spanning across three continents.
Danfoss Turbocor Compressors
Danfoss Scrolls
Danfoss Optyma Condensing Units
Danfoss Maneurop Reciprocating Compressors
Danfoss Light Commercial Refrigeration
Compressors
Our products can be found in a variety of applications such as rooftops, chillers, residential air conditioners,
heatpumps, coldrooms, supermarkets, milk tank cooling and industrial cooling processes.
http://cc.danfoss.com
Danfoss Commercial Compressors, BP 331, 01603 Trévoux Cedex, France | +334 74 00 28 29