Danfoss MTZ56HL4BVE Maneurop Reciprocating Compressor

Danfoss Maneurop MTZ56HL4BVE Hermetic Reciprocating Compressor

The Danfoss Maneurop MTZ56HL4BVE is an evaporating temperature hermetic reciprocating compressor engineered for commercial, industrial, and marine refrigeration systems. Built around an internal circular gas-cushioned motor design, the MTZ series is purpose-engineered to withstand hostile operating environments, high suction superheat conditions, and liquid floodback risks common in shipboard provisions, cargo hold refrigeration, and industrial chiller circuits.

The MTZ56HL4BVE utilizes Danfoss POE lubricant 175PZ, providing full compatibility with hydrofluorocarbon (HFC) and hydrofluoroolefin (HFO) blends including R134a, R404A, R407A/C/F, R448A, R449A, and R452A. It features an internal relief valve, an internal motor protection line break, threaded sight-glass accommodation for optical oil level monitoring, and industry-standard Rotolock service connections that eliminate the need for line-torching during overhaul or replacement.

Technical Details:

Terminal Allocations & Wiring Schematic

• Terminal 1 (L1 / U): Phase A Line In
• Terminal 2 (L2 / V): Phase B Line In
• Terminal 3 (L3 / W): Phase C Line In
• Ground (PE): Direct chassis ground stud (tightened to 3.0 Nm)

Primary Applications

• Marine Provision Refrigeration Units: Deep-freeze meat/fish rooms (-25°C to -18°C) and vegetable cold rooms (+2°C to +4°C) operating under constant ambient engine-room heat.
• Shipboard Air Conditioning & Deck Cranes: Cab cooling, wheelhouse HVAC, galley package units, and hydraulic deck winch cooling circuits.
• Supermarket & Commercial Cold Rooms: Walk-in storage freezers, walk-in coolers, blast chillers, and display cabinets using centralized R404A or R449A systems.
• Industrial Process Chillers: Closed-loop fluid chillers, pharmaceutical process coolers, and offshore oil platform environmental control systems.

Compatible Equipment Models

• Danfoss Optyma & Optyma Plus Condensing Units: Fits models MGZ056, OP-MPUM056, OP-LPUM056.
• Marine & Industrial Package Chiller Brands: Carrier Transicold, Sabroe/Johnson Controls, Daikin Marine, Bitzer packaged retrofits, Novenco, Dometic Marine provision packs.
• Replacement Scenarios: Direct drop-in mechanical replacement for legacy Maneurop MT56 series compressors transitioning from R22 mineral-oil circuits to HFC/HFO refrigerants (requires complete R22 line blow-through).

Part Number Cross-References

• Danfoss Ordering Code (Industrial Pack): MTZ56-4VI, MTZ56-4VM
• Danfoss Single Pack Code: MTZ56HL4BVE, MTZ56HL4DVE
• Global EAN Barcode: 5702428980500 / 5702428866996
• Legacy Model Cross-Reference: Replaces Maneurop MT56HL4BVE / MT056-4 (when flushing mineral oil for POE conversions).

Our Engineering Expert’s Guide

1) The Marine Engineer’s Vacuum & Moisture Rule

Maneurop MTZ series compressors use Danfoss 175PZ POE lubricant, which is hydroscopic. If you are replacing a burnt-out or open compressor onboard:

• Never leave the compressor shipping plugs uncapped for longer than 15 minutes.
• Evacuate the system down to at least 0.67 mbar (500 microns) and hold for a 30-minute rise test to ensure absolute dehydration before opening the service valves.

2) Rotolock Torque & Gasket Alignment

Never reuse Teflon Rotolock gasket washers. When reinstalling service valves:

• Torque the 1-3/4″ Suction Rotolock union nut to 110 Nm (81 ft-lbs).
• Torque the 1-1/4″ Discharge Rotolock union nut to 90 Nm (66 ft-lbs).
• Overtightening distorts the internal Teflon seat, while undertightening causes slow micro-leaks under constant shipboard diesel vibration.

3) Crankcase Heater Operational Interlock

In marine installations subject to tropical-to-temperate ambient swings, migration of liquid refrigerant to the compressor shell during compressor shutdown is the primary cause of broken discharge reeds on startup. Verify that the crankcase heater has been continuously energized for at least 12 hours prior to initial start. The oil sump temperature must sit at least 10 K to 15 K above saturation temperature.

4) Phase Sequence & Single-Phasing Safeguards

Because the MTZ56 uses internal line-break protection rather than external phase monitoring:

• Verify phase balancing across all legs. Phase unbalance in voltage must not exceed 2%.
• A 2% voltage unbalance creates up to a 14% to 18% current unbalance in the stator windings, generating hotspot failures that trip the internal Klixon prematurely.

Frequently Asked Questions

What oil does the Danfoss MTZ56HL4BVE use, and can mineral oil be added?

The MTZ56HL4BVE is factory-charged with 1.8 liters of Danfoss 175PZ Polyolester (POE) oil. You must never mix mineral oil or alkylbenzene lubricants into an MTZ compressor. Mixing mineral oil with POE reduces oil return, clouds the sight glass, and causes carbonization at high discharge temperatures.

Can the MTZ56HL4BVE directly replace an older Danfoss Maneurop MT56-4VI compressor?

Yes. Mechanically, the mounting footprint (190 mm x 190 mm), Rotolock union threads (1-3/4″ suction, 1-1/4″ discharge), and overall height (413 mm) are identical. However, the MT56 used mineral oil for R22 systems. If swapping in an MTZ56, the line set and evaporator must be thoroughly flushed to remove residual mineral oil below 1% concentration before charging with alternative HFC refrigerants.

What should the balanced winding resistance read across terminals?

On a healthy MTZ56 motor stator at standard ambient reference (25°C), the resistance between any two phase terminals (T1-T2, T2-T3, T1-T3) must read approximately 2.44 Ohms. A resistance variance greater than 0.2 Ohms between phases or any continuity to ground indicates insulation degradation or burned stator turns.

What is the maximum number of compressor starts permitted per hour?

The MTZ56 is rated for a maximum of 12 starts per hour. Cycle rates higher than this induce high thermal and inductive shock to the motor windings, dramatically reducing insulation life and risking early contactor pitting. Implement an anti-recycle timer set to a minimum run/rest interval of at least 3 to 5 minutes.