Danfoss Maneurop NTZ Series Instruction Manual

Maneurop® reciprocating
compressors NTZ
R404A - R507 - R452A
Application guidelines
http://cc.danfoss.com

Content
Maneurop® reciprocating compressors............................................................................................. 5
Features .................................................................................................................................................................................5
Specifications....................................................................................................................................... 6
Technical specifications and nominal ratings..........................................................................................................6
Versions..................................................................................................................................................................................6
Compressor reference ......................................................................................................................................................6
Nominal performance data for R404A and R452A.................................................................................................7
Dimensions .......................................................................................................................................... 8
1 cylinder...............................................................................................................................................................................8
2 cylinders.............................................................................................................................................................................9
4 cylinders..........................................................................................................................................................................10
Electrical connections and wiring .................................................................................................... 11
Voltage application range............................................................................................................................................11
Single phase electrical characteristics.....................................................................................................................11
Nominal capacitor values and relays........................................................................................................................11
Single phase motor protection and suggested wiring diagram....................................................................11
Trickle circuit.....................................................................................................................................................................11
PSC wiring..........................................................................................................................................................................11
CSR wiring..........................................................................................................................................................................11
Single phase PSC wiring with trickle circuit ..........................................................................................................12
Single phase CSR wiring with trickle circuit ..........................................................................................................12
Single phase CSR wiring without trickle circuit....................................................................................................12
Three phase electrical characteristics......................................................................................................................13
Three phase motor protection and suggested wiring diagram.....................................................................13
Wiring diagram with pump-down cycle.................................................................................................................13
Wiring diagram without pump-down cycle..........................................................................................................14
IP rating...............................................................................................................................................................................14
Motor protection.............................................................................................................................................................14
Voltage unbalance..........................................................................................................................................................14
Approval and certifications .............................................................................................................. 15
Approvals and certificates............................................................................................................................................15
Pressure equipment directive 2014/68/EU............................................................................................................15
Low voltage directive 2014/35/EU............................................................................................................................15
Machinery directive 2014/30/EU...............................................................................................................................15
Internal free volume.......................................................................................................................................................15
Operating conditions ........................................................................................................................ 16
Refrigerants and lubricants .........................................................................................................................................16
Operating envelope .......................................................................................................................................................16
R404A / R507.....................................................................................................................................................................16
R452A ..................................................................................................................................................................................16
Discharge temperature protection...........................................................................................................................17
Operating limits...............................................................................................................................................................17
System design recommendations.................................................................................................... 18
Piping design....................................................................................................................................................................18
Suction line........................................................................................................................................................................18
Discharge line...................................................................................................................................................................18
Oil charge and oil separator........................................................................................................................................19
Filter driers.........................................................................................................................................................................19
Suction pressure control...............................................................................................................................................19
Suction line heat exchanger........................................................................................................................................19
Cycle rate limit..................................................................................................................................................................20
Liquid refrigerant control and charge limits .........................................................................................................20
Off-cycle migration.........................................................................................................................................................20
Liquid floodback during operation ..........................................................................................................................20
Crankcase heater.............................................................................................................................................................21
Liquid line solenoid valve & pump-down ..............................................................................................................21
Suction accumulator......................................................................................................................................................21
3FRCC.PC.046.A4.02
Application Guidelines

Content
Sound and vibration management.................................................................................................. 22
Sound ..................................................................................................................................................................................22
Vibration.............................................................................................................................................................................22
Installation and service..................................................................................................................... 23
System cleanliness..........................................................................................................................................................23
Compressor handling, mounting and connection .............................................................................................23
Compressor connection to the system ...................................................................................................................24
System pressure test ......................................................................................................................................................24
Leak detection..................................................................................................................................................................25
Vacuum pump-down and dehydration procedure ............................................................................................25
Start-up...............................................................................................................................................................................25
Refrigerant charging......................................................................................................................................................25
Oil charge and oil level..................................................................................................................................................26
Installation checks ..........................................................................................................................................................26
Ordering information and packaging.............................................................................................. 27
Code numbers..................................................................................................................................................................27
Packaging...........................................................................................................................................................................27
Accessories......................................................................................................................................... 28
FRCC.PC.046.A4.024
Application Guidelines

Maneurop® reciprocating compressors
Features The Maneurop® NTZ series from Danfoss
Commercial Compressors is a range of hermetic
reciprocating compressors for low evaporating
temperature applications. These compressors
replace the former LTZ range.
The NTZ series is engineered as a true low
temperature compressor, optimised with
R404A at -35°C with an extended evaporating
temperature range from -45°C up to -10°C. The
compressors can be operated at a return gas
temperature (suction gas temperature) of 20°C
even at low evaporating temperatures.
A liquid injection system is not required. All
components are of high quality and precision to
assure a long product life.
NTZ compressors have a large internal free
volume that helps to reduce the risk of liquid
hammering. The electrical motor is fully suction
gas cooled which means that no additional body
cooling is required and it allows the compressor
to be insulated with an acoustic hood when the
installation requirements call for extra low sound
characteristics.
5FRCC.PC.046.A4.02
Application Guidelines

Specifications
Compressor
model
Swept
volume
cm3/rev
Displacement Nominal ratings* Number
of
cylinders
Oil
charge
litre
Net
weight
kg
50 Hz
2900 rpm
m3/hr
60 Hz
3500 rpm
m3/hr
50 Hz 60 Hz
Cooling
capacity W COP W/W Cooling capacity W COP W/W
NTZ048 48 8.4 10.1 995 1.15 1190 1.13 10.95 21
NTZ068 68 11.8 14.3 1749 1.15 2065 1.15 10.95 23
NTZ096 96 16.7 20.2 2002 1.15 2395 1.16 21.8 35
NTZ108 108 18.7 22.6 2465 1.16 2788 1.10 21.8 35
NTZ136 136 23.6 28.5 3225 1.11 3739 1.12 21.8 35
NTZ215 215 37.5 45.2 4948 1.19 5886 1.19 43.9 62
NTZ271 271 47. 3 57.0 6955 1.24 8058 1.21 43.9 64
(*) Motor code 4 operating conditions: R404A, Evap. temp.: -35°C, Cond. temp.: 40°C, RGT: 20°C, SC: 0K
For full NTZ data details and capacity tables refer to Online Datasheet Generator: www.danfoss.com/odsg
NT Z 4 L048 A R1 B
Motor voltage code
Z: Polyolester lubricant
Displacement in cm³ / rev.
UL index indicator
NT: New low temperature
reciprocating compressors
Evolution index,
B - R404A / R507 / R452A
Oil Charged 175PZ
A - Phased out
Equipment version
(R1: Rotolock connections,
oil equalisation connection
and sight glass)
Motor protection
(L: Internal Motor Protection)
Compressor reference
(indicated on the compressor
nameplate)
Technical specifications
and nominal ratings
Versions Available equipment version:
• R1: Rotolock suction and discharge connections, 3/8" flare oil equalisation connection, threaded
sight glass.
FRCC.PC.046.A4.026
Application Guidelines

Specifications
Nominal performance data for R404A and R452A
R404A Refrigeration
Compressor
model
50 Hz, EN12900 ratings
To = -35°C, Tc = 40°C, SC = 0K, SH = 10K 50 Hz, EN12900 ratings To = -35°C, Tc = 40°C, SC = 0K, RGT = 20°C
Cooling
capacity
W
Power
input
kW
Current
input
A
COP
W/W
Cooling
capacity
W
Power
input
kW
Current
input
A
COP
W/W
NTZ048-4 860 0.87 2.08 0.99 990 0.87 2.08 1.15
NTZ068-4 1510 1.52 3.42 1.00 1750 1.52 3.42 1.15
NTZ096-4 1730 1.73 3.29 1.00 2000 1.73 3.29 1.15
NTZ108-4 2130 2.08 4.53 1.02 2470 2.08 4.53 1.19
NTZ136-4 2790 2.90 6.10 0.96 3230 2.90 6.1 1.11
NTZ215-4 4280 4.15 7. 52 1.03 4950 4.15 7. 52 1.19
NTZ271-4 6010 5.62 9.65 1.07 6960 5.62 9.65 1.24
R404A Refrigeration
Compressor
model
60 Hz, EN12900 ratings
To = -35°C, Tc = 40°C, SC = 0K, SH = 10K 60 Hz, EN12900 ratings To = -35°C, Tc = 40°C, SC = 0K, RGT = 20°C
Cooling
capacity
W
Power
input
kW
Current
input
A
COP
W/W
Cooling
capacity
W
Power
input
kW
Current
input
A
COP
W/W
NTZ048-4 1030 1.06 1.99 0.97 1190 1.06 1.99 1.13
NTZ068-4 1790 1.79 3.42 1.00 2070 1.79 3.42 1.15
NTZ096-4 2070 2.06 3.30 1.00 2390 2.06 3.30 1.16
NTZ108-4 2410 2.53 4.50 0.95 2790 2.53 4.50 1.10
NTZ136-4 3230 3.35 5.67 0.96 3740 3.35 5.67 1.12
NTZ215-4 5050 4.90 7.52 1.03 5840 4.90 7.52 1.19
NTZ271-4 7090 6.64 9.65 1.07 8210 6.64 9.65 1.24
R452A Refrigeration
Compressor
model
50 Hz, EN12900 ratings
To = -35°C, Tc = 40°C, SC = 0K, SH = 10K 50 Hz, EN12900 ratings To = -35°C, Tc = 40°C, SC = 0K, RGT = 20°C
Cooling
capacity
W
Power
input
kW
Current
input
A
COP
W/W
Cooling
capacity
W
Power
input
kW
Current
input
A
COP
W/W
NTZ048-4 850 0.79 1.85 1.08 960 0.79 1.85 1.22
NTZ068-4 1490 1.28 3.31 1.16 1680 1.28 3.31 1.31
NTZ096-4 1820 1.65 3.25 1.10 2060 1.65 3.25 1.25
NTZ108-4 2090 1.98 4.32 1.06 2370 1.98 4.32 1.20
NTZ136-4 2950 2.78 6.11 1.06 3350 2.78 6.11 1.21
NTZ215-4 4210 3.98 7.30 1.06 4780 3.98 7.30 1.20
NTZ271-4 5580 5.00 8.94 1.12 6330 5.00 8.94 1.27
R452A Refrigeration
Compressor
model
60 Hz, EN12900 ratings
To = -35°C, Tc = 40°C, SC = 0K, SH = 10K 60 Hz, EN12900 ratings To = -35°C, Tc = 40°C, SC = 0K, RGT = 20°C
Cooling
capacity
W
Power
input
kW
Current
input
A
COP
W/W
Cooling
capacity
W
Power
input
kW
Current
input
A
COP
W/W
NTZ048-4 1100 1.04 1.96 1.06 1250 1.04 1.96 1.20
NTZ068-4 1700 1.51 3.16 1.13 1930 1.51 3.16 1.28
NTZ096-4 2230 2.05 3.43 1.09 2530 2.05 3.43 1.24
NTZ108-4 2820 2.50 4.64 1.13 3190 2.50 4.64 1.28
NTZ136-4 3560 3.33 6.13 1.07 4030 3.33 6.13 1.21
NTZ215-4 5330 4.96 7.72 1.07 6050 4.96 7.72 1.22
NTZ271-4 7050 6.47 9.85 1.09 8000 6.47 9.85 1.24
Note: R404A data is also valid for refrigerant R507.
7FRCC.PC.046.A4.02
Application Guidelines

Dimensions
Rotolock connections size Pipe sizing Rotolock valve
Suction Discharge Suction Discharge Suction Discharge
NTZ048
NTZ068 1"1/4 1" 5/8" 1/2" V09 V06
Oil equalisation
3/8"
PTC crankcase heater
25
98
Schrader
1/4"
263
333
353 (NTZ068-1)
Suction rotolock
1"1/4
Discharge rotolock
1"
68
82
109 118
35° 33°
68
Suc
tion 147
Discharge 142
159
17
17°
123
39
Threaded oil
sight glass
141
ø 224
68
HM8-40
23
15
Silent block
IP rating: 55 (with cable gland)
Spade connectors
1/4" AMP-AWE
Earth M4-12
Ø 21 mm
Knock-out Ø 21 mm
Terminal box
1 cylinder
FRCC.PC.046.A4.028
Application Guidelines

Dimensions
Rotolock connections size Pipe sizing Rotolock valve
Suction Discharge Suction Discharge Suction Discharge
NTZ096 - NTZ108 1"3/4 1"1/4 7/8" 3/4" V07 V04
NTZ136 1"3/4 1"1/4 1"1/8 3/4" V02 V04
(1) NTZ096 - 108
(2) NTZ136-1
98 (1)
117 (2)
60 156
8
Suction 179
Discharge 176
252
ø 288
413
32
Threaded oil
sight glass
Schrader
1/4"
PTC
crankcase heater
96
21
145
125
188
171
8
38
82 (1)
98 (2)
74 68
265
Suction rotolock
1"3/4
Discharge rotolock
1"1/4
Oil equalisation
3/8"
HM8-40
23
15
Silent block
IP rating: 55 (with cable gland)
Spade connectors
1/4" AMP-AWE
Earth M4-12
Ø 21 mm
Knock-out Ø 21 mm
Terminal box (1)
IP rating: 54 (with cable gland)
Terminal box (2)
2 cylinders
9FRCC.PC.046.A4.02
Application Guidelines

Dimensions
Rotolock connections size Pipe sizing Rotolock valve
Suction Discharge Suction Discharge Suction Discharge
NTZ215 - NTZ271 1"3/4 1"1/4 1"1/8 3/4" V02 V04
Ø 352
518
117
155
232
99
Oil equalisation
3/8"
Mounting hole for
PTC crankcase heater
15°
15°
15°
246
205
155°
246
Suction rotolock
1"3/4
Discharge rotolock
1"1/4
233
210
125
209
98
95
Threaded oil
sight glass
Schrader 1/4 "
30
19
HM12-50
Silent block
IP rating: 54 (with cable gland)
Terminal box
4 cylinders
FRCC.PC.046.A4.0210
Application Guidelines

Electrical connections and wiring
Motor voltage code Nominal voltage Voltage application range
1208-230V/1/60Hz 187–253V
3200-230V/3/60Hz 180–253V
4380-400V/3/50Hz
460V/3/60Hz 340–440V (50Hz) 414–506V (60Hz)
5220-240V/1/50Hz 198–264V
9380V/3/60Hz* 342–418V
LRA - Locked Rotor
Current (A) MCC - Maximum Continuous Current (A) Winding resistance (Ω) ( ± 7 % at 20° C)
Motor Code 1 5 1 5 1 5
Winding run start run start
NTZ048 43.7 37 13.7 11 1.32 4.16 1.62 3.95
NTZ068 72 53 21 17 0.94 2.01 1.05 3.19
NTZ096 97 31 0.45 1.84
NTZ108 97 33 0.45 1.84
NTZ136 140 41 0.36 1.73
Models
PSC/CSR* CSR only
Run capacitors (1) Start capacitors (2) Start
relay
(A) µF (C) µF (B) µF
50 Hz NTZ048 20 10 100
RVA6AMKL
NTZ068 20 10 100
60 Hz
NTZ048 15 10 100
NTZ068 25 25 135
NTZ096 30 15 135
NTZ108 30 15 135
NTZ136 30 15 135
Voltage application range
Single phase electrical
characteristics
Nominal capacitor values
and relays
* PSC: Permanent Split Capacitor
CSR: Capacitor Start Run
(1) Run capacitors: 440 volts
(2) Start capacitors: 330 Volts
Single phase motor
protection and suggested
wiring diagram
Single phase compressor motors are internally
protected by a temperature / current-sensing
bimetallic protector which senses the main and
start winding current as well as motor winding
temperature. If the motor were to be overloaded
and the protector trips, it might take up to
several hours to reset and restart the compressor.
The trickle circuit provides the facility of heating
the compressor crankcase by feeding a small
current to the auxiliary winding and the run
capacitor (See the drawings in section “Electrical
connections and wiring”).
For the larger single phase compressor models
NTZ048-068, the use of the PTC crankcase heater
is recommended.
PSC wiring may be used for refrigerant circuits
with capillary tubes or expansion valves with
bleed ports. Pressure equalisation must be
ensured before start-up because of the low
starting torque characteristics of this system.
CSR wiring provides additional motor torque
at start-up, by the use of a start capacitor in
combination with the run capacitor. This system
can be used for refrigerant circuits with capillary
tubes or expansion valves. The start capacitor is
only connected during the starting operation, a
potential relay is used to disconnect it after the
start sequence.
Some applications with high differential pressure
can require a very high starting torque. For such
cases the CSR starting kit can be converted to
a very high starting torque kit by an additional
start capcitor of 100 μF parallel to the start
capacitor of the CSR kit. This configuration
can also be used to reduce erratic starting
at unfavourable conditions such as very low
ambient temperature or weak voltage.
Trickle circuit
PSC wiring
CSR wiring
* Some models are approved for 380-400V/60Hz. Please check data sheet.
11FRCC.PC.046.A4.02
Application Guidelines

Electrical connections and wiring
Single phase PSC wiring
with trickle circuit
IOL Motor protector
A & C Run capacitors
C Common
S Start winding (auxiliary)
R Run winding (main)
Single phase CSR wiring
with trickle circuit
IOL Motor protector
A & C Run capacitors
B Start capacitor
C Common
S Start winding (auxiliary)
R Run winding (main)
IOL Motor protector
A + C Run capacitors
B Start capacitor
C Common
S Start winding (auxiliary)
R Run winding (main)
CapacitorsAandCarereplacedbyasingle
capacitor of size A + C
Single phase CSR wiring
without trickle circuit
FRCC.PC.046.A4.0212
Application Guidelines

Electrical connections and wiring
PTC
FU
FU
C1
EC
TH
N
L1
L2
L3
C1
MS
IOL
Comp.
FU Fuses
MS Main switch
C1 Compressor contactor
TH Thermostat
EC External controls
COMP Compressor
PTC Crankcase heater
IOL Internal overload line break
Three phase electrical
characteristics
Compressor
model
LRA
(Locked Rotor Amp) A MCC (Maximum Continuous Current) A Winding resistance (between phases +/- 7% at 25°C) Ohm
349349349
NTZ048 32 16 22 10.1 4.8 52.80 11. 55 7. 3
NTZ068 48.5 25 29 14.8 8.4 8.5 1.58 6.67 9.70
NTZ096 72 32 20.4 10.1 1.20 5.03
NTZ108 72 45 57 21.4 12.1 11 1.20 4.00 2.54
NTZ136 97. 2 51 64 29 14.3 15 0.98 3.80 2.54
NTZ215 147.7 74 110 42.3 22.3 23 0.57 2.23 1.26
NTZ271 198 96 150 56.5 27.0 30 0.41 1.61 0.84
Three phase motor
protection and suggested
wiring diagram
M
DGT
HP
180 s
TH
LP
CONTROL CIRCUIT
F1F1
KM
KM
KM
KA KA
A1
A2
A3
KA
KA
KS
KS
KS
L1 L3 L2
Q1
T1
T3
T2
LLSV KS
Wiring diagram with
pump-down cycle
Control device TH
Optional short cycle timer (3 min) 180 s
Control relay KA
Liquid Solenoid valve LLSV
Compressor contactor KM
Safety lock out relay KS
Pump-down control & L.P. switch BP
H.P. switch HP
Fused disconnect Q1
Fuses F1
Compressor motor M
Discharge gas thermostat DGT
13FRCC.PC.046.A4.02
Application Guidelines

Electrical connections and wiring
KM
L1 L3 L2
Q1
CONTROL CIRCUIT
F1F1
KM KA
KA KS
KS
KS
LP
HP
DGT
TH
180 s
85 52 019 - A
T1 T2
M
T3
KA KA
A1
A2
A3
Wiring diagram without
pump-down cycle
Control device TH
Optional short cycle timer (3 min) 180 s
Control relay KA
Compressor contactor KM
Safety lock out relay KS
H.P. switch HP
Fused disconnect Q1
Fuses F1
Compressor motor M
Discharge gas thermostat DGT
IP rating The compressor terminal boxes IP rating
according to CEI 529 are:
IP55 for NTZ048-136 except NTZ136-1
IP54 for NTZ136-1 & NTZ215-271
The IP ratings are only valid when correctly sized
cable glands of the same IP rating are applied.
Vavg = Mean voltage of phases 1, 2 and 3
V1-2 = Voltage between phases 1 and 2
V1-3 = Voltage between phases 1 and 3
V2-3 = Voltage between phases 2 and 3.
|Vavg - V1-2 |+|Vavg - V1-3 |+|Vavg - V2-3 |
2 xVavg
% voltage unbalance: x 100
Internal motor protection
Voltage unbalance
Motor protection
Three phase compressors are internally
protected by a temperature / current-sensing
bimetallic protector, connected to the neutral
point of the star-connected stator windings.
This internal overload line break protects the
motor against overheating, current overload and
locked rotor conditions. If the motor were to be
overloaded and the protector trips, all 3-phases
are cut out. It might take up to several hours to
reset and restart the compressor.
Operating voltage limits are shown in section
"Voltage application range". The voltage applied
to motor terminals must lie within these limits
during both start-up and normal operation.
The maximum allowable voltage unbalance is
2%. Voltage unbalance causes high amperage
on one or more phases, which in turn leads to
overheating and possible motor damage.
The voltage unbalance is given by the following
formula:
FRCC.PC.046.A4.0214
Application Guidelines

Approval and certifications
Products NTZ 048 to 068 NTZ 096 to 271
Refrigerating fluids Group 2 Group 2
Category PED III
Evaluation module out of the scope D1
Maximum / Minimum allowable temperature - TS 50°C > Ts > -35°C 50°C > Ts > -35°C
Maximum allowable pressure - PS 22.6 bar 22.6 bar
Products NTZ 048 to 271
Declaration of conformity Contact Danfoss
Products NTZ 048 to 271
Manufacturer's declaration of incorporation Contact Danfoss
CE
(European Directive) All models
UL
(Underwriters Laboratories) All models (Except NTZ108/136/215/271 code9)
CCC (China Compulsory
Product Certification) Models with motor voltage code 4&5. NTZ271-4 is out of CCC scope
EAC Eurasian conformity mark Models with motor voltage code 4&5
Approvals and
certificates
Pressure equipment
directive 2014/68/EU
Low voltage directive
2014/35/EU
Machinery directive
2014/30/EU
Internal free volume
Maneurop® NTZ compressors comply with the
following approvals and certificates.
Other certificates/approvals please contact
Danfoss.
Products Internal free volume without oil (litre)
Low pressure side High pressure side Total
NTZ048-068 7.5 0.3 7.8
NTZ096-108-136 16.5 0.6 17.1
NTZ215-271 31 1.2 32.2
15FRCC.PC.046.A4.02
Application Guidelines

Operating conditions
Model Refrigerant Type* GWP** Temp.glide*** (K) Lubricant
NTZ
R404A HFC 3922 0.7/0.3
175PZ POE chargedR507 HFC 3985 0/0
R452A HFC+HFO 2141 3.9/3.7
*Type: HFC: Hydrofluorcarbon (no chlorine component, "long-term" zero-ODP alternative)
**GWP: Global Warning Potential
*** Temperature glide: difference between saturated vapor temperature and saturated liquid temperature at constant pressure
RGT 20°C
SH = 10K
NTZ / R452A
Operating envelope
Refrigerants and
lubricants
Because of their thermodynamic properties,
R404A and R507 are especially suitable for low
and medium temperature applications. Danfoss
recommends the use of these refrigerants with
NTZ compressors. Note that R404A has a small
temperature glide. It must therefore be charged
in the liquid phase. For most other aspects
however, this small glide may be neglected. R507
is an azeotropic mixture without temperature
glide.
Because of its thermodynamic properties R452A
is suitable for low temperature applications.
R452A has a medium glide of 4K and must
therefore to be charged in the liquid phase.
Maneurop® NTZ compressors are designed and
optimised for refrigerants R404A / R507 / R452A.
The use of hydrocarbons is not authorised in NTZ
compressors.
Only approved refrigerants and lubricants as
listed in below table may be used.
R404A / R507
R452A
FRCC.PC.046.A4.0216
Application Guidelines

Operating conditions
NTZ – R404A / R507 R452A
Working pressure range, high side (bar gauge) 13.2 – 27.7 12.5 - 24.2
Working pressure range, low side (bar gauge) 0.05 – 3.3 0.18 - 3
Minimum low pressure safety switch setting (bar gauge) 0 0.13
Minimum low pressure pump-down switch setting (bar gauge) 0.21 0.35
Relief valve opening pressure difference (2 and 4 cyl) (bar) 30 30
Relief valve closing pressure difference (bar) 8 8
Low pressure
Operating limits
High pressure
A low-pressure (LP) safety switch must also be
used; deep vacuum operations will result in
failure. The minimum LP safety switch (loss of
charge switch) setting is 0 relative bar (0 bar
g). For systems without pump-down feature,
the LP safety switch must be either a manual
lockout device or an automatic LP safety switch
wired into an electrical lockout circuit. LP switch
tolerance must not allow for vacuum operation
of the compressor. LP safety switch settings for
pump-down cycles with automatic reset are
listed in the following table.
A high-pressure (HP) safety switch is required to
shut down the compressor should the discharge
pressure exceed the values shown in the table
below. This switch can be set at lower values
depending on the application and ambient
conditions. It must be either located in a lockout
circuit or associated with a manual reset device
to prevent cycling around the high pressure limit.
If a discharge valve is used, the HP switch must
be connected to the service valve gauge port,
which cannot be isolated.
Thermostat
Insulation
Bracket
Discharge line
Discharge temperature
protection
Even when the motor windings are protected
against overheating by the internal motor
protection, the compressor discharge gas
temperature could exceed the maximum
allowed value of 135°C when the compressor
is operated outside its application envelope.
The most effective protection against too
high discharge gas temperature is to mount
a discharge gas thermostat. An accessory kit
is available from Danfoss which includes the
thermostat, mounting bracket and insulation.
The thermostat must be attached to the
discharge line as indicated below at no more
than 150 mm from the discharge connection.
17FRCC.PC.046.A4.02
Application Guidelines

System design recommendations
Suction line
Piping design
Horizontal suction line sections shall have a
slope of 0.5% in the direction of refrigerant flow
(5 mm per meter).The cross-section of horizontal
suction lines shall be such that the resulting
gas velocity is at least 4 m/s. In vertical risers, a
gas velocity of 8 to 12 m/s is required to ensure
proper oil return.
A U-trap is required at the foot of each vertical
riser. If the riser is higher than 4 m, additional
U-traps are required for each additional 4 meters.
The length of each U-trap must be as short as
possible to avoid the accumulation of excessive
quantities of oil (see figure below).
Gas velocities higher than 12 m/s will not
contribute to significantly better oil return.
However they will cause higher noise levels
and result in higher suction line pressure
drops which will have a negative effect on the
system capacity. Note that the suction rotolock
valves, which can be ordered from Danfoss
as accessories, are designed for average pipe
sizes, selected for systems running at nominal
conditions. The pipe sizes selected for specific
systems may differ from these average sizes.
The suction line must always be insulated to limit
suction gas superheat.
Oil in a refrigeration circuit is required to
lubricate moving parts in the compressor. During
normal system operation small oil quantities
will continuously leave the compressor, with
the discharge gas. Therefore, the system piping
shall be designed in a way which allows a good
oil circulation, avoiding oil being trapped in
the system and ensuring a constant oil return
to the compressor. As long as the amount of
oil circulating through the system is small it
will contribute to good system operation and
improved heat transfer efficiency.
Lubricant getting trapped in the evaporator or
suction lines will affect system performance and
will ultimately lead to compressor lubrication
failures. Where a poor oil return situation exists,
adding lubricant will not help safeguard the
compressor. Only a correct piping design can
ensure adequate oil circulation maintaining safe
oil level in the compressor.
Maneurop® NTZ compressors have been
designed and qualified for stationary equipment
using standard alternating power supply.
Danfoss does not warrant the compressors
for use on mobile applications such as trucks,
railways, subways, ships etc.
Discharge line When the condenser is mounted above the
compressor, a loop above the condenser and a
U-trap close to the compressor are required to
prevent liquid draining from the condenser into
the discharge line during standstill.
FRCC.PC.046.A4.0218
Application Guidelines

System design recommendations
Oil charge and oil
separator
Filter driers
Suction pressure control
Suction line heat
exchanger
In most installations the initial compressor oil
charge will be sufficient. In installations with line
runs exceeding 20 m, or with many oil traps or an
oil separator, additional oil may be required. In
installations with the risk of slow oil return such
as in multiple evaporator or multiple condenser
installations, an oil separator is recommended.
Also refer to the section "Oil charge and oil level".
For new installations with NTZ compressors
Danfoss recommends using the Danfoss DML
100% molecular sieve, solid core filter drier.
Molecular sieve filter driers with loose beads
from third party suppliers shall be avoided.
For servicing of existing installations where acid
formation is present the Danfoss DCL solid core
filter driers containing activated alumina are
recommended.
The drier is to be oversized rather than
undersized. When selecting a drier, always
take into account its capacity (water content
capacity), the system refrigerating capacity and
the system refrigerant charge.
An MOP-type expansion valve or suction
pressure regulator (i.e. Danfoss KVL) must be
used to limit suction pressure at a maximum of
4 bar relative (-5°C). Do not apply both of these
devices in combination with one another.
When compressors are mounted onto a rack
for a multi-evaporator system (i.e. supermarket)
or when evaporators operate at different
temperatures, use pressure regulators (Danfoss
KVP) without an MOP expansion valve.
A suction line heat exchanger is recommended
for low temperature applications, better
performance and efficiency are expected.
However in hot location this may cause high
suction gas superheat which can result in too
high discharge temperature.
Low ambient temperature
operation
At low ambient temperatures, the condensing
temperature and condensing pressure in air
cooled condensors will decrease. This low
pressure may be insufficient to supply enough
liquid refrigerant to the evaporator. As a result
the evaporating temperature will decrease,
leading to low capacity and eventual poor oil
return. At start-up, the compressor will pull into
vacuum and it will be switched off by the low
pressure protection. Depending on how the low
pressure switch and delay timer are set, short
cycling can occur. To avoid these problems,
several solutions are possible, based on reducing
condenser capacity:
In air-cooled machines, cycling the fans with
a head pressure controller will ensure that the
fans remain off until the condensing pressure
has reached a satisfactory level. Variable speed
fans can also be used to control the condensing
pressure. In water-cooled units, the same can
be performed using a water regulator valve
that is also operated by head pressure, thereby
ensuring that the water valve does not open until
the condensing pressure reaches a satisfactory
level.
The minimum condensing pressure must be
set at the minimum saturated condensing
temperature shown in the application envelopes.
Under very low ambient conditions, in which
testing has revealed that the above procedures
might not ensure satisfactory condensing and
suction pressures, the use of a head pressure
control valve is recommended. Note: This
solution requires extra refrigerant charge, which
can introduce other problems. A non-return
valve in the discharge line is recommended and
special care should be taken when designing the
discharge line.
When the compressor is located in a low ambient
temperature environment, increased refrigerant
migration will occur during shut down periods.
For such conditions an extra belt-type crankcase
heater is strongly recommended.
Note that with 100% suction gas cooled motors,
Maneurop® compressors can be externally
insulated. Refer to section "Liquid refrigerant
migration & charge limits" for more details.
19FRCC.PC.046.A4.02
Application Guidelines

System design recommendations
Cycle rate limit No more than 12 starts per hour (6 when a soft
start accessory is used) are allowed. A higher
number would reduce the service life of the
motor-compressor unit. If necessary, use an anti-
short-cycle timer within the control circuit.
The system must be designed in a way that
guarantees minimum compressor running time
so as to provide sufficient motor cooling after
start-up as well as proper oil return from the
system to the compressor.
A 5-minute delay between two successive
compressor starts is being proposed herein,
with a 2-minute runtime after each start and a
3-minute idle time between each stop and start.
Only during the pump-down cycle may the
compressor run for much shorter intervals.
Liquid floodback during
operation
Off-cycle migration
Liquid refrigerant control
and charge limits
During normal and stable system operation,
refrigerant will leave the evaporator in a
superheated condition and enter the compressor
as a superheated vapour. Normal superheat
values at compressor suction are 5 to 30 K.
However the refrigerant leaving the evaporator
can contain an amount of liquid refrigerant due
to different reasons:
• wrong dimensioning, wrong setting or
malfunction of expansion device
• evaporator fan failure or frosted-up evaporator
coils.
In these situations, liquid refrigerant will
continuously enter the compressor. The negative
effects from continuous liquid floodback are:
• permanent oil dilution
• in extreme situations with high system
refrigerant charge and large amounts of
floodback, liquid slugging could occur.
During system standstill and after pressure
equalisation, refrigerant will condensate in
the coldest part of the system which may be
the compressor when it is placed in a cold
environment. Ultimately, the full system
refrigerant charge can condensate in the
compressor crankcase. A large amount will
dissolve in the compressor oil until the oil is
completely saturated with refrigerant. When
the compressor is started, the pressure in the
crankcase decreases rapidly and refrigerant
will violently evaporate, causing the oil to foam
(boiling). Both dilution and foaming reduce
the lubrication properties of the oil. In extreme
situations liquid could enter the compressor
cylinders with immediate compressor break-
down as a result.
Refrigeration compressors are basically
designed as gas compressors. Depending on the
compressor design and operating conditions,
most compressors can also handle a limited
amount of liquid refrigerant. Maneurop® NTZ
compressors have a large internal volume and
can therefore handle relatively large amounts of
liquid refrigerant without major problems.
However even when a compressor can handle
liquid refrigerant, this will not be favourable to
its service life.
Liquid refrigerant will dilute the oil, wash out the
bearings causing wear and eventually seizure.
Furthermore, high oil carry over will cause lack of
oil in the sump.
Good system design can limit the amount of
liquid refrigerant in the compressor, which will
have a positive effect on the compressor service
life.
Liquid refrigerant can enter a compressor in
various ways, with different effects on the
compressor as described in the following points.
FRCC.PC.046.A4.0220
Application Guidelines