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System design recommendations

Suction accumulator: 

a suction accumulator 

offers protection against refrigerant flood back 
at start-up, during operations or defrosting by 
trapping the liquid refrigerant upstream from 
the compressor. The suction accumulator also 
protects against off-cycle migration by providing 
additional internal free volume to the low side of 
the system.

A suction accumulator must be carefully 
dimensioned, taking into account the refrigerant 
charge as well as the gas velocity in the suction 
line. Depending on the operating conditions it 
may happen that the recommended connections 
of the accumulator are one size smaller than the 
suction line.

Liquid flood back

During normal operation, refrigerant enters the 
compressor as a superheated vapour. Liquid 
flood back occurs when a part of the refrigerant 
entering the compressor is still in liquid state.

A continuous liquid flood back will cause oil 
dilution and, in extreme situations lead to lack 
of lubrication and high rate of oil leaving the 
compressor.

Liquid flood back test

 - Repetitive liquid flood 

back testing must be carried out under TXV 
threshold operating conditions: a high pressure 
ratio and minimum evaporator load, along with 
the measurement of suction superheat, oil sump 
temperature and discharge gas temperature.

During operations, liquid flood back may be 
detected by measuring either the oil sump 
temperature or the discharge gas temperature. 
If at any time during operations, the oil sump 
temperature drops to within 10K (18°F) or less 
above the saturated suction temperature, or 

should the discharge gas temperature be less 
than 35K (65°F) above the saturated discharge 
temperature, this indicates liquid flood back. 

Continuous liquid flood back can occur with 
a wrong dimensioning, a wrong setting or 
malfunction of the expansion device or in case of 
evaporator fan failure or blocked air filters.

A suction accumulator providing additional 
protection as explained hereunder can be used 
to solve light continuous liquid flood back.

•  While the thermostat is off, the number of 

pressure switch resets should be limited to 
avoid short cycling of the compressor. Use 
dedicated wiring and an additional relay which 
allows for one shot pump-down.

The pump-down allows to store all the refrigerant 
in the high pressure side circuit. On unitary 
or close-coupled systems, where the system 
refrigerant charge is expected to be both correct 
and definable the entire system charge may be 
stored in the condenser during pump-down if all 
components have been properly sized.

Other application needs a liquid receiver to store 
the refrigerant.

Receiver dimensioning requires special attention. 
The receiver shall be large enough to contain 
part of the system refrigerant charge but it shall 
not be dimensioned too large. A large receiver 
easily leads to refrigerant overcharging during 
maintenance operation.

AB243286444663en-001003

33

Application Guidelines

Summary of Contents for MLZ Evolution A

Page 1: ...Danfoss Scroll for Refrigeration MLZ Evolution A with POE Oil 50 60 Hz R404A R507 R134a R22 R407A R407F R448A R449A R452A R513A Application guidelines www danfoss com ...

Page 2: ......

Page 3: ...temperature 23 Application envelope 23 Maximum discharge gas temperature 28 High and low pressure protection 29 On off cycling cycle rate limit 29 System design recommendations 30 General 30 Essential piping design considerations 30 Refrigerant charge limit 31 Off cycle migration 31 Liquid flood back 33 Specific application recommendations 34 Low ambient application 34 Scroll and reciprocating 34 ...

Page 4: ...fer cooling capacity from 3 4 to 21kW 2 to 10HP at common voltages and frequencies as well as any of the common refrigerants R404A R507 R134a R22 R407A R407F R448A R449A R452A R513A Thanks to its dedicated refrigeration design the MLZ scroll compressor delivers a number of powerful advantages With its high efficiency motor and optimised scroll design it reduces energy cost in normal operating cond...

Page 5: ...s compression pockets between the two scroll elements Low pressure suction gas is trapped within each crescent shaped pocket as it forms continuous motion of the orbiting scroll serves to seal the pocket which decreases in volume as the pocket moves towards the centre of the scroll set with corresponding increase in gas pressure Maximum compression is achieved as the pocket reaches the discharge p...

Page 6: ...timised for refrigeration Motor protection L Internal motor protection Tubing and electrical connections P Brazed connections spade terminals C Brazed connections screw terminals T Rotolock connections spade terminals Q Rotolock connections screws terminals Motor voltage code 1 208 230V 1 60Hz 2 200 220V 3 50Hz 208 230V 3 60Hz 4 380 415V 3 50Hz 460V 3 60Hz 5 220 240V 1 50Hz 7 575V 3 60Hz 9 380V 3 ...

Page 7: ...48A MLZ015 2 3200 11000 1 68 1 91 6 52 33 8 2 06 5 9 208 1 1 37 31 68 MLZ019 2 5 4200 14300 2 11 1 99 6 79 43 5 2 65 7 6 268 1 1 37 31 68 MLZ021 3 4400 15000 2 23 1 97 6 73 46 2 2 82 8 0 283 1 1 37 31 68 MLZ026 3 5 5500 18700 2 78 1 97 6 72 57 1 3 48 9 9 350 1 1 37 31 68 MLZ030 4 6600 22500 3 17 2 08 7 09 68 8 4 20 12 0 424 1 6 54 37 81 MLZ038 5 7800 26600 3 64 2 14 7 30 81 0 4 94 14 1 498 1 6 54 ...

Page 8: ...0 15800 53925 8 04 1 96 6 69 162 4 9 91 28 3 999 2 7 91 45 99 R452A MLZ015 2 3400 11500 1 71 1 97 6 72 33 8 2 06 5 9 208 1 1 37 31 68 MLZ019 2 5 4300 14700 2 17 1 99 6 80 43 5 2 65 7 6 268 1 1 37 31 68 MLZ021 3 4600 15700 2 27 2 02 6 89 46 2 2 82 8 0 283 1 1 37 31 68 MLZ026 3 5 5700 29400 2 81 2 02 6 90 57 1 3 48 9 9 350 1 1 37 31 68 MLZ030 4 6800 23400 3 27 2 10 7 18 68 8 4 20 12 0 424 1 6 54 37 ...

Page 9: ...R448A MLZ015 2 3800 13100 1 96 1 96 6 69 33 8 2 06 7 1 251 1 1 37 31 68 MLZ019 2 5 5100 17400 2 48 2 06 7 02 43 5 2 65 9 1 321 1 1 37 31 68 MLZ021 3 5400 18400 2 62 2 06 7 03 46 2 2 82 9 7 343 1 1 37 31 68 MLZ026 3 5 6800 23200 3 21 2 12 7 23 57 1 3 48 12 0 424 1 1 37 31 68 MLZ030 4 6600 22500 3 17 2 08 7 09 68 8 4 20 14 5 512 1 6 54 37 81 MLZ038 5 8200 28100 3 72 2 22 7 56 81 0 4 94 17 0 600 1 6 ...

Page 10: ... 91 34 1 1204 2 7 91 45 99 R452A MLZ015 2 4100 13900 2 05 1 99 6 78 33 8 2 06 7 1 251 1 1 37 31 68 MLZ019 2 5 5200 17900 2 57 2 03 6 94 43 5 2 65 9 1 321 1 1 37 31 68 MLZ021 3 5500 18800 2 70 2 05 6 99 46 2 2 82 9 70 343 1 1 37 31 68 MLZ026 3 5 6800 23300 3 34 2 04 6 97 57 1 3 48 12 0 424 1 1 37 31 68 MLZ030 4 8400 28700 3 94 2 14 7 29 68 8 4 20 14 5 512 1 6 54 37 81 MLZ038 5 9800 33300 4 55 2 15 ...

Page 11: ...231 393 Schrader valve and cap Oil sight glass All dimensions in mm inch P T terminal box type 1 7 0 06 41 1 61 Ø 41 Ø 1 61 29 5 1 16 5 16 18 UNC self tapping Recommended torque for mounting bolts 11Nm 1Nm Ø11 Ø0 43 not supply with the grommet 239 9 40 7 50 4x Ø0 75 4x Ø19 0 Ø163 5 165 5 Discharge line Ø1 00 14UN 2A Suction line Ø1 1 4 12UN 2A Oil sight glass Schrader valve and cap 129 5 07 110 72...

Page 12: ... 19 4 x Ø 0 75 5 27 7 50 4 64 17 16 10 27 2 20 0 74 0 43 C Q terminal box type C T1 S T2 R T3 1 7 0 06 41 1 61 Ø 41 Ø 1 61 29 5 1 16 5 16 18 UNC self tapping Recommended torque for mounting bolts 11Nm 1Nm Ø11 Ø0 43 not supply with the grommet Rotolock Brazed 121 2 4 77 suction line 95 25 134 120 3 4 73 92 0 94 0 403 2 202 4 261 Oil sight glass Schrader 435 9 19 11 34 31 45 2 239 190 Ø182 54 184 54...

Page 13: ...4 31 45 73 190 232 9 13 7 50 4 92 125 4 x Ø 19 4 x Ø 0 75 0 74 C Q terminal box type C T1 S T2 R T3 1 7 0 06 41 1 61 Ø 41 Ø 1 61 29 5 1 16 5 16 18 UNC self tapping Recommended torque for mounting bolts 11Nm 1Nm Ø11 Ø0 43 not supply with the grommet 232 9 13 7 50 124 9 4 91 suction line 133 31 73 45 2 119 27 Ø185 Ø7 28 350 134 7 19 Suction line Ø1 3 4 12UN 2A Oil sight glass Schrader valve and cap ...

Page 14: ...ncorporating a schrader valve Torque requirements Schrader valve core 0 6 0 2Nm 0 44 0 14lb ft Schrader valve cover 14 5 1Nm 10 7 0 7lb ft Schrader Compressor models Brazed connection size Rotolock adaptor set adaptor gasket sleeve nut Rotolock adaptor adaptor only Rotolock Solder sleeve ODF Code Number Code Number MLZ 015 019 021 026 Suction 3 4 1 1 4 3 4 120Z0126 120Z0366 Discharge 1 2 1 1 2 120...

Page 15: ...r Care must be taken during installation to ensure that the compressor operates in the correct direction see Phase sequence and reverse rotation protection The drawings below show electrical terminal labelling and should be used as a reference when wiring the compressor For three phase applications the terminals are labelled T1 T2 and T3 For single phase applications the terminals are labelled C c...

Page 16: ...LZ019T7 38 7 0 5 4 5 4 7 3 7 3 MLZ021T7 38 8 0 5 5 5 4 7 3 7 3 MLZ026T7 38 9 0 6 0 5 4 7 3 7 3 MLZ030T7 42 9 0 7 8 4 4 4 5 4 4 MLZ038T7 53 11 5 9 4 4 0 3 9 4 0 MLZ045T7 64 11 5 11 3 2 8 2 9 2 9 MLZ048T7 67 14 12 3 2 6 2 6 2 5 MLZ058T7 75 16 14 4 2 3 2 3 2 3 MLZ066T7 95 17 16 3 2 0 2 0 2 0 MLZ076T7 100 20 19 1 1 7 1 7 1 7 Motor voltage code 9 380V 3ph 60Hz MLZ015T9 40 7 5 6 0 3 2 4 4 4 4 MLZ019T9 5...

Page 17: ...al starting current to the motor s start winding The current passing through the PTC causes it to heat up and at a certain temperature change to a very high resistance At this time the motor is up to nominal speed and the run capacitor determines the current through the start winding The PTC remains at high temperature and thus at high resistance as long as power is connected to the compressor Whe...

Page 18: ...omponents for CSR wiring PSC wiring CSR wiring Run capacitor Start capacitor Relay µF µF Reference 220 240V 1 50Hz Motor voltage code 5 MLZ015 40 145 175 3ARR3 3AL RVA3EKL MLZ019 021 026 70 145 175 3ARR3 3AL RVA3EKL MLZ030 50 161 193 3ARR3 24AP RVA3EKL MLZ038 042 55 88 108 3ARR3 25AS RVA4GKL 208 230V 1 60Hz Motor voltage code 1 not provided with the compressor MLZ015 45 145 175 3ARR3 3M RVA2ACKL M...

Page 19: ...or three phase applications the voltage measured at the compressor terminals for each phase should be within 2 of the average for all phases Phase sequence and reverse rotation protection Voltage imbalance Internal motor protection MLZ scroll compressors are equipped with an internal line break protector mounted on the motor windings The protector is an automatic reset device containing a snap act...

Page 20: ...Danfoss Products Internal free volume at LP side without oil MLZ 015 026 1 85 litre 113 in 3 MLZ 030 048 3 44 litre 210 in 3 MLZ 058 076 6 15 litre 375 in 3 Pressure equipment directive 2014 68 EU Machinery directive 2006 42 EC annex II b Low voltage directive 2014 35 EU Electromagnetic compatibility 2014 30 EU Products MLZ 015 to 076 Refrigerating fluids Group 2 Category PED I Evaluation module n...

Page 21: ...n HFO refrigerant with properties comparable to R404A R507 has no ozone depletion potential ODP 0 As with R404A R507 is particularly suitable for low evaporating temperature applications but it can also be used for medium evaporating temperature applications R507 is an azeotropic mixture with no temperature glide R407A and R407F are two HFC refrigerants with similar properties Both have a GWP belo...

Page 22: ... with POE compressor could replace it As PVE oil is fully miscible with POE Danfoss recommends the POE oil RL46HB regardless of oil charge in the compressor Replacement POE RL46HB oil is available for topping up or replacing oil in the field see section Accessory Designation Composition ODP GWP Safety group Boiling temp C F Temp glide C F Critical temp C F Critical pressure bar Cond temp 26bar C F...

Page 23: ...mperatures as per the operating envelopes MLZ compressors can be applied from 35 C 31 F to 55 C 131 F ambient temperature The compressors are designed as 100 suction gas cooled without need for additional fan cooling Ambient temperature has very little effect on the compressor performance In case of enclosed fitting and high ambient temperature it s recommend to check the temperature of power wire...

Page 24: ... temperature F Condensing temperature C Condensing temperature F SH 11K 19 8 F SH 10K 18 F RGT 20 C 68 F MLZ015 066 R407A 5 10 15 20 25 30 35 40 45 50 55 60 65 41 50 59 68 77 86 95 104 113 122 131 140 149 30 25 20 15 10 5 0 5 10 15 22 13 4 5 14 23 32 41 50 59 Evaporating temperature C Evaporating temperature F Condensing temperature C Condensing temperature F AB243286444663en 001003 24 Application...

Page 25: ...ature F Condensing temperature C Condensing temperature F SH 10K 18 F RGT 20 C 68 F MLZ015 066 R407F 5 10 15 20 25 30 35 40 45 50 55 60 65 30 25 20 15 10 5 0 5 10 15 Evaporating temperature C Evaporating temperature F Condensing temperature C Condensing temperature F 41 50 59 68 77 86 95 104 113 122 131 140 149 22 13 4 5 14 23 32 41 50 59 SH 10K 18 F RGT 20 C 68 F AB243286444663en 001003 25 Applic...

Page 26: ... 50 59 41 50 59 68 77 86 95 104 113 122 131 140 149 SH 10K 18 F RGT 20 C 68 F MLZ R22 10 15 20 25 30 35 40 45 50 55 60 65 70 75 50 59 68 77 86 95 104 113 122 131 140 149 158 167 35 30 25 20 15 10 5 0 5 10 15 20 31 22 13 4 5 14 23 32 41 50 59 68 Evaporating temperature C Evaporating temperature F Condensing temperature C Condensing temperature F SH 11K 19 8 F RGT 25 C 77 F AB243286444663en 001003 2...

Page 27: ...5 40 45 50 55 60 65 41 50 59 68 77 86 95 104 113 122 131 140 149 SH10K 18 F RGT 20 C 68 F MLZ R452A Condensing temperature C Condensing temperature F Evaporating temperature C Evaporating temperature F 35 30 25 20 15 10 5 0 5 10 15 31 22 13 4 5 14 23 32 41 50 59 5 10 15 20 25 30 35 40 45 50 55 60 65 41 50 59 68 77 86 95 104 113 122 131 140 149 SH10K 18 F RGT 20 C 68 F AB243286444663en 001003 27 Ap...

Page 28: ...ge temperature depends mainly on the combination of evaporating temperature condensing temperature and suction gas superheat Discharge gas temperature should be controlled with an isolated thermocouple or thermostat attached to the discharge line 15 cm 6 inches from the compressor shell Maximum discharge gas temperature must not exceed 135 C 275 F when the compressor is running within the approved...

Page 29: ... MLZ058 076 scroll compressors are not equipped with an internal pressure relief valve therefore a high pressure switch is required to shut down the compressor should the discharge pressure exceed the values shown in the table above The high pressure switch can be set to lower values depending on the application and ambient conditions The HP switch must either be placed in a lockout circuit or con...

Page 30: ... when stopped see fig 2 The maximum elevation difference between the indoor and outdoor section cannot exceed 8 m System manufacturers should specify precautions for any applications that exceed these limits to ensure compressor reliability Piping should be designed with adequate three dimensional flexibility figure 2 It should not be in contact with the surrounding structure unless a proper tubin...

Page 31: ...the risk of off cycle migration is the following Stabilize the non running system at 5 C 41 F ambient temperature Raise the ambient temperature to 20 C 68 F and keep it for 10 minutes Start the compressor and monitor sump temperature sight glass indication and sound level The presence of liquid in the crankcase can be easily detected by checking the sump level through the oil sight glass Foam in t...

Page 32: ...ng diagrams please see to section Electrical connections Models MLZ015 048 incorporate an internal low leak check valve that is appropriate for pump down operations This valve prevents the back flow of refrigerant from the high pressure to the low pressure side through the compressor so pump down conditions can be achieved and maintained Models MLZ058 076 are not equipped with this low leak check ...

Page 33: ...ing either the oil sump temperature or the discharge gas temperature If at any time during operations the oil sump temperature drops to within 10K 18 F or less above the saturated suction temperature or should the discharge gas temperature be less than 35K 65 F above the saturated discharge temperature this indicates liquid flood back Continuous liquid flood back can occur with a wrong dimensionin...

Page 34: ...ight 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 For further information please contact Danfoss Low ambient start up Und...

Page 35: ...g a brazed plate condenser heat exchanger a sufficient free volume for the discharge gas to accumulate is required in order to avoid excess pressure build up At least 1 meter of discharge line is necessary to generate this volume To help reduce the discharge gas volume immediately after start up the supply of cooling water to the heat exchanger may be opened before the compressor starts to remove ...

Page 36: ...ing power of lower frequency sound Use of sound insulation materials on the inside of unit panels is an effective means of substantially reducing the sound being transmitted to the outside Ensure that no components capable of transmitting sound vibration within the unit come into direct contact with any non insulated parts on the walls of the unit Because of the unique design of a full suction gas...

Page 37: ...ially transmitted to the frame The tubing should be designed so as to both reduce the transmission of vibrations to other structures and withstand vibration without incurring any damage Tubing should also be designed for three dimensional flexibility For more information on piping design please see the section entitled Essential piping design considerations Gas pulsation The MLZ scroll compressors...

Page 38: ...signed for Any other substances within the system will not improve performance and in most cases will be highly detrimental to system operations The presence of non condensable substances and system contaminants such as metal shavings solder and flux have a negative impact on compressor service life Many of these contaminants are small enough to pass through a mesh screen and can cause considerabl...

Page 39: ...azing material into the joint but not into the compressor Remove all remaining flux once the joint has been soldered with a wire brush or a wet cloth Remaining flux would cause corrosion of the tubing Ensure that no flux is allowed to enter into the tubing or compressor Flux is acidic and can cause substantial damage to the internal parts of the system and compressor The POE oil used in MLZ compre...

Page 40: ...nd storage Liquid line filter driers A properly sized type of drier is required Important selection criteria include the driers water content capacity the system refrigeration capacity and the system refrigerant charge The drier must be able to reach and maintain a moisture level of 50ppm end point dryness EPD Danfoss recommends DML 100 molecular sieve driers for MLZ compressors R404A R507 R134a R...

Page 41: ...onnection Included Included 4 grommets per compressor Included Included 4 assemblies of self tapping US thread bolt washer sleeve per compressor Not included Included 4 sleeves per compressor Included Included Quantity for full pallets Single packs can be ordered per 1 Stacking only allowed for full pallets with identical products per pallet Made from US Danfoss pallets Optimized for overseas cont...

Page 42: ...809 121L8815 MLZ058 T Q 9 121L8817 121L8819 121L8825 MLZ066 T Q 9 121L8827 121L8829 121L8853 MLZ076 T Q 9 121L8835 121L8837 121L8843 Compressors Model Variation Connections Features Voltage Code 1 Voltage Code 2 Voltage Code 4 Voltage Code 5 Voltage Code 9 Danfoss palette MLZ015 T T 9 121L8708 121L8710 121L8844 MLZ019 T T 9 121L8718 121L8722 121L8726 121L8730 121L8734 MLZ021 T T 9 121L8736 121L873...

Page 43: ...120U8677 120U8645 120U8697 MLZ042 T C 9 120U8789 MLZ045 T C 9 120U8679 120U8649 120U8801 120U8699 MLZ048 T C 9 120U8681 120U8651 120U8811 120U8701 MLZ058 T C 9 120U8683 120U8653 120U8821 120U8703 MLZ066 T C 9 120U8685 120U8657 120U8831 MLZ076 T C 9 120U8687 120U8655 120U8839 Brazed version Rotolock version Compressors Model variation Connections Features Voltage code 1 Voltage code 2 Voltage code ...

Page 44: ...6 120U8676 120U8644 120U8646 120U8696 MLZ042 T C 9 120U8788 MLZ045 T C 9 120U8678 120U8648 120U8800 120U8698 MLZ048 T C 9 120U8680 120U8650 120U8810 120U8700 MLZ058 T C 9 120U8682 120U8652 120U8820 120U8702 MLZ066 T C 9 120U8684 120U8656 120U8830 MLZ076 T C 9 120U8686 120U8654 120U8838 Brazed version Rotolock version Compressors Model variation Connections Features Voltage code 1 Voltage code 2 Vo...

Page 45: ... 042 60HZ Motor Code 1 MLZ MLM038 Multipack 10 50μF 8173233 PSC wiring Run Capacitor 50μF 50Hz Motor Code 5 MLZ MLM030 Multipack 10 45μF 8173232 PSC wiring Run Capacitor 45μF 60Hz Motor Code 1 MLZ MLM015 019 021 Multipack 10 40μF 8173231 PSC wiring Run Capacitor 40μF 50Hz Motor Code 5 MLZ MLM015 Multipack 10 Type Code n Description Application Packaging Pack size 145 175μF 120Z0399 CSR wiring Star...

Page 46: ...ck 50 Code n Description Application Packaging Pack size 7968004 Rotolock valve V06 1 Rotolock 1 2 ODF Discharge MLZ015 026 045 Industry pack 50 8168031 Rotolock valve V06 1 Rotolock 1 2 ODF Multipack 6 7968006 Rotolock valve V04 1 1 4 Rotolock 3 4 ODF Suction MLZ015 026 Discharge MLZ048 Industry pack 42 8168029 Rotolock valve V04 1 1 4 Rotolock 3 4 ODF Multipack 6 7968007 Rotolock valve V05 1 1 4...

Page 47: ...LZ015 019 021 026 Multipack 6 118U0057 IP54 upgrade kit for square terminal box MLZ030 038 042 045 048 058 076 Multipack 6 Acoustic hood Terminal box Code No Description Application Packaging Pack Size 120Z5083 Acoustic hood MLZ015 019 021 026 Single pack 1 120Z5084 Acoustic hood MLZ030 038 042 045 048 Single pack 1 120Z5085 Acoustic hood MLZ058 066 076 Single pack 1 Code No Description Applicatio...

Page 48: ...itioned us as distinct variable speed technology specialists Today we operate from engineering and manufacturing facilities spanning across three continents AB243286444663en 001003 Danfoss DCS CC 2020 06 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 ww...

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