I charged the compressor CAJ4519Z with R407 gas, and upon startup, some frost appeared on the return line and expansion valve, even though the cooling was fine. Is this normal? Note that it’s a refrigeration room, not a freezer.
Category: Refrigeration
written by www.mbsmpro.com | January 26, 2026
Regarding the compressor in the photo (Tecumseh CAJ4519Z) used in a cold room (chilling/positive temperature) with R-407C gas, finding frost on the suction line and the expansion valve is not normal for this type of application.
While the cooling might seem “good” now, frost on the suction line indicates that liquid refrigerant is not fully evaporating in the evaporator and is returning to the compressor.
Here is a technical breakdown of why this is happening and how to fix it:
1. Low Superheat (Expansion Valve Adjustment)
This is the most common cause. If the expansion valve is open too wide, it allows too much liquid into the evaporator.
The Risk: Liquid refrigerant can reach the compressor (Liquid Slugging), which can break the internal valves of the CAJ4519Z compressor.
The Fix: You need to adjust the Superheat. For a positive temperature cold room, the superheat should be between 5°C and 8°C. If it is lower, slightly close the expansion valve (turn the adjustment screw clockwise) in half-turn increments and wait 15–20 minutes to see the effect.
2. Overcharging the System
If you added too much R-407C, the excess refrigerant stays in the evaporator and suction line as a liquid/gas mix, causing frosting.
Note on R-407C: This is a “blend” refrigerant. It must always be charged in the liquid state (tank upside down). If you charged it as a vapor, the mixture ratio might be wrong, affecting performance.
The Fix: Check the sight glass (if available) and monitor the pressures. For R-407C in a cold room at 0°C to +4°C, your suction pressure should typically be around 45 to 55 PSI.
3. Poor Airflow at the Evaporator
If the heat exchange is poor, the refrigerant won’t boil off into a gas.
Check the Evaporator (EVACOND unit in your photo):
Are the fans spinning at the correct speed?
Are the fins dirty or clogged?
Is there already an ice buildup on the evaporator coils blocking the air?
4. Expansion Valve Sensing Bulb
Check the location of the expansion valve’s sensing bulb.
If the bulb is loose or not insulated properly, it “thinks” the pipe is warm and opens the valve too much, flooding the suction line.
The Fix: Ensure the bulb is tightly clamped to the suction pipe (at the 2 o’clock or 10 o’clock position) and well-insulated.
Summary Recommendation:
Frost should generally stop at the outlet of the expansion valve or the very beginning of the evaporator. If the frost is traveling all the way back to the compressor:
Slightly close the expansion valve.
Verify the airflow over the evaporator.
Ensure you haven’t overcharged the system.
Allowing frost to reach the compressor will eventually lead to mechanical failure or “slugging,” which will destroy the compressor.
Focus Keyphrase: Comprehensive Technical Guide for Tecumseh CAJ4519Z Compressor Performance in R407C and R404A Medium High Back Pressure Refrigeration Systems
Meta Description: Explore the professional specifications of the Tecumseh CAJ4519Z compressor. Learn about its 1 HP capacity, multi-refrigerant compatibility, and expert field advice for maintaining optimal superheat in commercial cold rooms.
Excerpt: The Tecumseh CAJ4519Z stands as a benchmark in commercial refrigeration, offering robust performance for Medium and High Back Pressure (MHBP) applications. Engineered for versatility, it supports a wide array of refrigerants including R404A and R407C. This professional analysis covers technical data, wiring configurations, and essential maintenance practices for field engineers working on refrigeration units.
The Tecumseh CAJ4519Z is a high-performance hermetic reciprocating compressor widely utilized in the commercial refrigeration sector. Known for its reliability in medium to high evaporating temperature ranges, this unit is a staple for walk-in coolers, display cases, and industrial liquid chillers. Its “AJ” series design focuses on thermal efficiency and mechanical durability, making it a preferred choice for technicians demanding longevity in demanding environments.
Technical Specification Table
Attribute
Specification Details
Model
CAJ4519Z
Utilisation
MHBP (Medium/High Back Pressure)
Domaine
Cooling / Air Conditioning / Commercial Chilling
Oil Type and Quantity
POE (Polyolester) / 887 ml
Horsepower (HP)
1 HP (Nominal)
Refrigerant Type
R404A, R448A, R449A, R452A, R22, R407C
Power Supply
220-240V ~ 50Hz
Cooling Capacity BTU
~15,500 BTU/h (at +7.2°C Evaporating Temp)
Motor Type
CSR (Capacitor Start – Run)
Displacement
34.4 cm³
Winding Material
High-Grade Copper
Pressure Charge
High Pressure (Nitrogen Holding Charge)
Capillary / Expansion
Expansion Valve (TXV) Recommended
Compatible Equipment
Cold Rooms, Bottle Coolers, Industrial Chillers
Temperature Function
-15°C to +15°C (Evaporating Range)
Fan Requirement
Forced Air Cooling Required (350 m³/h minimum)
Commercial Use
Yes, Heavy-Duty Commercial Grade
Amperage (RLA)
6.5 A
LRA (Locked Rotor Amps)
45 A
Type of Relay
Potential Relay
Start/Run Capacitor
Start: 88-108µF / Run: 20µF
Comparison with Peer Models
When evaluating the CAJ4519Z, it is helpful to compare its displacement and capacity against other industry standards in the 1 HP range.
Feature
Tecumseh CAJ4519Z
Embraco NEK6217GK
Danfoss SC15GH
Displacement
34.4 cm³
14.3 cm³ (LBP/HBP Mix)
15.28 cm³
Cooling Power
High (Multi-Ref)
Medium (R404A)
Medium (R134a)
System Design
CSR
CSIR
CSIR/CSR
Oil Compatibility
Multi-Refrigerant POE
POE Only
POE/PAG
Engineering Insights: Managing Frost and Superheat
In field operations, specifically when retrofitting or charging systems with R407C, technicians may encounter frost on the suction line. From an engineering perspective, frost migrating toward the compressor crankcase is a critical warning sign.
Diagnostic Checkpoint:
Superheat Calibration: For a positive temperature cold room, the target superheat at the evaporator outlet should be between 5K and 8K. If frost reaches the suction service valve, the superheat is likely near zero, risking liquid slugging.
R407C Glide: Unlike R404A, R407C has a significant temperature glide. Charging must be performed in the liquid phase to maintain the correct blend ratio.
Expansion Valve Tuning: If the cooling is effective but frosting occurs, the Thermostatic Expansion Valve (TXV) may be adjusted too “open.” Closing the valve (clockwise) increases superheat and retreats the frost line.
The CSR (Capacitor Start – Run) motor configuration is designed for high starting torque.
Common (C): Connected to the Overload Protector.
Start (S): Connected to the Potential Relay (Terminal 2) and Start Capacitor.
Run (R): Connected to the Main Power and Run Capacitor.
Potential Relay: Terminals 1 and 2 disconnect the start capacitor once the motor reaches ~75% speed.
Expert Advice and Notice
Notice: Always use a filter drier compatible with POE oil. POE is highly hygroscopic (absorbs moisture rapidly).
Benefit: The CAJ4519Z features an internal pressure relief valve, providing an extra layer of safety against system over-pressurization.
Engineering Tip: When using R407C, ensure the condenser is sized for the additional heat rejection requirements compared to R22. Failure to do so will result in high head pressures and reduced compressor lifespan.
Discover the technical specifications for the Copeland CS16K6E-PFZ-155 compressor. High-performance 1.25 HP hermetic reciprocating unit for R404A/R507 refrigeration systems.
The Copeland CS16K6E-PFZ-155 is a high-efficiency hermetic reciprocating compressor designed for commercial refrigeration. Operating at 220-240V and 50Hz, this 1.25 HP powerhouse is optimized for R404A and R507 refrigerants. Known for its durability in medium-temperature applications, it features POE oil and thermal protection, making it a reliable choice for cold rooms and professional cooling systems.
When it comes to commercial refrigeration, the reliability of the compressor is the heartbeat of the system. The Copeland CS16K6E-PFZ-155 stands out as a robust solution for professionals seeking a balance between high-torque performance and long-term durability. This hermetic reciprocating compressor is specifically engineered for medium-temperature applications, utilizing modern HFC refrigerants.
Technical Deep Dive: The CS16K6E-PFZ-155
The CS series from Copeland is famous for its “tough-as-nails” construction. The CS16K6E-PFZ-155 model operates on a single-phase 220-240V power supply at 50Hz. With a Locked Rotor Amperage (LRA) of 68.6A, it provides the necessary starting torque to handle demanding commercial environments, such as walk-in coolers and display cases.
Core Specifications Table
Feature
Specification
Brand
Copeland (Emerson)
Model Number
CS16K6E-PFZ-155
Horsepower (HP)
1.25 HP (Approx. 1-1/4 HP)
Refrigerant
R404A, R507, R452A
Oil Type
45 POE (Polyolester Oil)
Voltage/Frequency
220-240V / 50Hz / 1 Phase
Locked Rotor Amps (LRA)
68.6 A
Cooling Capacity
~13,500 – 16,000 BTU/hr (at MBP)
Application
Medium Temperature (MBP)
Comparative Analysis: Copeland CS vs. Competition
To understand where the CS16K6E fits in the market, it is helpful to compare it with similar models from other industry leaders like Tecumseh and Danfoss.
Performance Comparison Table
Model
Brand
Displacement
HP Class
Refrigerant
CS16K6E-PFZ
Copeland
29.3 cm³
1.25 HP
R404A
CAE4456Z
Tecumseh
14.5 cm³
0.5 HP
R404A
SC18MLX
Danfoss
17.7 cm³
0.75 HP
R404A
MTZ022
Danfoss
38.1 cm³
1.75 HP
R404A
While the CS16K6E sits comfortably in the 1.25 HP range, it often outperforms competitors in high-ambient conditions due to its superior thermal protection and larger internal volume, which helps in heat dissipation.
Why Choose the CS16K6E-PFZ-155?
The “E” in the model name indicates that this unit is pre-charged with POE oil. This is crucial for systems using R404A, as POE oil is miscible with HFCs, ensuring proper lubrication return to the crankcase.
Key Advantages:
High Starting Torque (HST): Ideal for systems using expansion valves where pressure might not be fully equalized at start-up.
Internal Thermal Protection: Automatically shuts down the motor in case of overheating, preventing catastrophic coil failure.
Compact Footprint: Fits into standard condensing units, making it an excellent choice for field replacements.
Maintenance and Installation Best Practices
To ensure the longevity of your Copeland CS16K6E-PFZ-155, certain installation standards must be met. Since this unit uses POE oil, it is highly hygroscopic (it absorbs moisture quickly).
Vacuum Level: Ensure the system is evacuated to at least 500 microns to remove all moisture.
Filter Drier: Always replace the liquid line filter drier whenever the system is opened.
Voltage Stability: Ensure the 220V supply stays within ±10% to avoid tripping the 68.6A LRA limit.
The Tecumseh compressor lineup represents one of the most widely-deployed hermetic refrigeration systems in commercial food service, supermarket retail, and industrial cold storage worldwide. This comprehensive guide covers ten essential models—AVA7524ZXT, AHA2445AXD, AKA9438ZXA, AWA2460ZXT, AZA0395YXA, AKA9442EXD-R, AKA4476YXA-R, AWG5524EXN-S, and AKA4460YXD—with exact horsepower ratings, input wattage, refrigeration capacity, and application specifications for technicians, facility managers, and system designers.
Complete Specifications Table: All Ten Tecumseh Compressor Models
Model
HP Rating
Input Watts (Rated)
Refrigeration Capacity (W)
Refrigerant
Voltage/Phase
Evaporating Range
Application Type
Motor Type
AVA7524ZXT
3 HP
3,490–4,000 W (varies by refrigerant)
6,639–6,973 W (R407A-R404A @ 20°F evap.)
R404A, R407A, R448A, R449A, R452A
200–230V 3-phase 60Hz / 50Hz
−23.3°C to −1.1°C (−10°F to 30°F)
Medium-Back-Pressure (MBP)
HST (High Start Torque) 3-phase
AHA2445AXD
1 HP
1,225 W (R-12 @ −10°F evap.)
1,289 W (legacy R-12)
R-12 (inactive/restricted)
200–230V 1-phase 50/60Hz
−40°C to −12.2°C (−40°F to 10°F)
Low-Back-Pressure (LBP)
CSIR (Capacitor-Start) HST
AKA9438ZXA
1/2 HP
756 W (R404A @ 20°F evap.)
1,099–1,112 W (R404A-R407A)
R404A, R407A, R448A, R449A, R452A
115V 1-phase 60Hz / 100V 50Hz
−17.8°C to 10°C (0°F to 50°F)
Commercial-Back-Pressure (CBP)
CSIR HST
AWA2460ZXT
1.5 HP
1,552–1,686 W (R452A-R449A)
1,684–1,758 W (−10°F evap.)
R404A, R407A, R448A, R449A, R452A
200–230V 3-phase 50/60Hz
−40°C to −12.2°C (−40°F to 10°F)
Low-Back-Pressure (LBP)
HST 3-phase
AZA0395YXA
1/9 HP
230 W (R134a @ 20°F evap.)
278 W (R134a)
R-134a
115V 1-phase 60Hz / 100V 50Hz
−17.8°C to 10°C (0°F to 50°F)
Commercial-Back-Pressure (CBP)
RSIR (Rotary Solenoid) LST
AKA9442EXD-R
1/2 HP
760 W (R-22 @ 20°F evap.)
1,231 W (R-22)
R-22, R-407C
208–230V 1-phase 60Hz / 200V 50Hz
−17.8°C to 10°C (0°F to 50°F)
Commercial-Back-Pressure (CBP)
CSR (Capacitor-Start) HST
AKA4476YXA-R
3/4 HP
1,070–1,111 W (R134a-R513A)
2,250–2,265 W (45°F evap.)
R-134a, R-513A
115V 1-phase 60Hz / 100V 50Hz
−6.7°C to 12.8°C (20°F to 55°F)
High-Back-Pressure (HBP)
CSIR HST
AWG5524EXN-S
2 HP
1,650–2,480 W (varies load)
7,091 W (R-22 rated)
R-22, R-407C
208–230V 1-phase 60Hz / 200–220V 50Hz
−23.3°C to 12.8°C (−10°F to 55°F)
Multi-Temperature
PSC LST
AKA4460YXD
1/2 HP
889–890 W (R134a HT)
6,250 BTU/h (~1,830 W) @ 20°F evap.
R-134a (high-temperature rated)
208–230V 1-phase 60Hz
−6.7°C to 12.8°C (20°F to 55°F)
High-Back-Pressure (HBP)
CSIR HST
Detailed Model Analysis with Exact Power Specifications
AVA7524ZXT: 3 HP, 3,490–4,000 W Medium-Back-Pressure Workhorse
The Tecumseh AVA7524ZXT is one of the company’s flagship 3-horsepower, three-phase compressors with input power consumption ranging from 3,490 W to 4,000 W depending on refrigerant and operating conditions. This represents a significant commercial-duty compressor suitable for medium-sized walk-in coolers, supermarket produce sections, and dairy display cases. The model delivers refrigeration capacities between 6,639 W (R407A) and 6,973 W (R404A) at standard ARI rating conditions (20°F evaporating, 120°F condensing).
Power Consumption Breakdown by Refrigerant at 20°F Evaporation:
R404A: 4,000 W input (Most demanding; highest discharge temperature)
R449A: 3,622 W input (Better efficiency than R404A)
R448A: 3,622 W input (Similar to R449A; lower GWP)
R452A: 3,772 W input (Improved efficiency; very low GWP)
R407A: 3,490 W input (Most efficient; legacy alternative)
The high three-phase inrush current (65.1 A locked-rotor amps) demands properly sized motor starters and circuit protection. Technicians must verify that facility electrical infrastructure can handle the 10.9 A rated load at 60 Hz continuously without voltage sag exceeding 3%.
Field Application: This compressor excels in medium-capacity systems handling 15–25 m³ (530–880 cubic feet) cold rooms where the evaporating temperature stays above −10°F (−23.3°C) and cooling loads are moderate to heavy. Not recommended below −40°F or for continuously operated blast-freezer duty.
AHA2445AXD: 1 HP, 1,225 W Legacy Low-Temperature R-12 Unit
The Tecumseh AHA2445AXD is a 1-horsepower, single-phase compressor rated for 1,225 W input power at the ASHRAE standard low-temperature rating (−10°F evaporating, 130°F condensing). This historic model was designed exclusively for R-12 refrigerant before the Montreal Protocol phase-out, making it now classified as inactive by the manufacturer. Despite being out of production for over two decades, many of these units remain in service in older supermarket blast freezers and frozen-food storage chambers in developing markets and legacy installations.
Critical Specifications:
Refrigeration Capacity: 1,289 W @ −10°F evaporation (ASHRAE standard)
Motor Configuration: CSIR (Capacitor-Start/Induction-Run) with High Start Torque
Locked-Rotor Amps: 51 A (high inrush current requiring heavy-duty contactors)
Displacement: 53.186 cc (relatively small piston chamber)
Oil Type: Mineral oil (incompatible with modern POE-based refrigerants)
Why It’s Obsolete: R-12 recovery is mandatory in most developed nations; supplies are restricted to legacy system maintenance only. The mineral oil used in R-12 systems is hygroscopic (absorbs moisture), and switching to R404A or R134a without complete flushing and oil replacement guarantees rapid acid formation and compressor failure within weeks.
Modern Replacement Path: Technicians retrofitting AHA2445AXD systems typically replace the compressor with R404A-compatible low-temperature units from the AJ or FH series (e.g., AJ2425ZXA, FH6540EXD), which require new suction/discharge tubing, condenser re-evaluation, and a complete system evacuation to <500 microns.
AKA9438ZXA: 1/2 HP, 756 W Compact Commercial Medium-Temperature
The Tecumseh AKA9438ZXA is a compact 1/2-horsepower compressor drawing just 756 W input power at R404A rating conditions (20°F evaporation). Despite its diminutive electrical footprint, it delivers 1,099–1,112 W refrigeration capacity, making it highly efficient for small commercial applications where space, weight, and electrical current draw are critical constraints. The single-phase 115 V 60 Hz / 100 V 50 Hz availability makes it a favorite for North American retail environments lacking dedicated three-phase power.
Performance and Electrical Profile:
Refrigerant
Input Watts
Capacity Watts
Locked-Rotor Amps
Rated Load Amps
R404A
800 W
1,099 W
58.8 A
9.2 A
R407A
756 W
1,112 W
58.8 A
9.2 A
R449A
724 W
1,094 W
58.8 A
9.2 A
R452A
757 W
1,092 W
58.8 A
9.2 A
R448A
724 W
1,094 W
58.8 A
9.2 A
Critical Field Consideration: The high locked-rotor current (58.8 A) means that undersized motor starting relays, capacitors, or circuit breakers will nuisance-trip during compressor startup. Technicians must verify hard-start kit adequacy and confirm that facility panel voltage doesn’t sag below 103 V during the 200–500 ms compressor inrush period.
Ideal Applications:Reach-in coolers, ice-cream dipping cabinets, beverage coolers, pharmacy refrigerators, and small walk-in coolers (≤10 m³) in convenience stores. The evaporating range of 0°F to 50°F (−17.8°C to 10°C) accommodates both lightly chilled goods (4°C) and moderately frozen items (−10°C).
AWA2460ZXT: 1.5 HP, 1,552–1,686 W Three-Phase Low-Temperature
The Tecumseh AWA2460ZXT is a 1.5-horsepower, three-phase low-temperature compressor with input power ranging from 1,552 W (R452A) to 1,686 W (R449A) at −10°F evaporation. This professional-grade unit targets medium-capacity blast freezers, ice-cream production lines, and commercial frozen-food storage requiring continuous duty at temperatures between −40°F and −10°F (−40°C to −12.2°C).
Power Efficiency Comparison Across Refrigerants (230 V 3-phase, −10°F evaporation):
Refrigerant
Input Watts
Refrigeration Capacity (W)
Efficiency (W/W)
Discharge Temp. Trend
R404A
1,630 W
1,758 W
1.08
Baseline
R449A
1,686 W
1,684 W
1.00
Higher; more discharge heat
R448A
1,686 W
1,684 W
1.00
Similar to R449A
R452A
1,552 W
1,719 W
1.11
Lowest input; best COP
Three-Phase Electrical Requirements:
Locked-Rotor Amps (LRA): 63.4 A (substantial; requires oversized contactor)
Displacement: 51.27 cc (large piston volume for high-displacement performance)
Operational Excellence: The AWA2460ZXT shines in consistent, heavy-duty freezer service where uninterrupted cooling at −20°F to −30°F is essential for product quality. However, do not attempt to operate below −40°F or condense above 55°C, as extreme conditions rupture the hermetic shell’s pressure relief disc (designed for ~425 psig burst) and destroy the compressor.
AZA0395YXA: 1/9 HP, 230 W Micro-Displacement Extended-Temperature
The Tecumseh AZA0395YXA represents a tiny 1/9-horsepower compressor with only 230 W input power consumption at ARI rating conditions (20°F evaporation, R134a). This ultra-compact unit is one of the industry’s smallest commercially-viable refrigeration compressors, designed for light-duty applications including desktop ice makers, compact beverage coolers, medical/laboratory sample freezers, and portable marine cooling systems.
Remarkable Compactness:
Weight: Only 19 lbs (8.6 kg)
Displacement: 5.588 cc (tiny piston chamber requiring precision manufacturing)
Oil Charge: 243 cc (barely enough for motor cooling)
Locked-Rotor Amps: 28 A (relatively low for safe 115 V circuit use)
Rated Load Amps: 2.9 A @ 115 V 60 Hz (draws less current than a desk lamp)
Capacity and Efficiency Profile:
Evaporating Temp.
Capacity BTU/h (W)
Input Watts
Power Factor
20°F (−6.7°C)
950 BTU/h (278 W)
230 W
1.21 W/W
25°F (−3.9°C)
1,230 BTU/h (360 W)
257 W
1.40 W/W
30°F (−1.1°C)
1,370 BTU/h (401 W)
274 W
1.46 W/W
Critical Limitation: The LST (Low-Start-Torque) RSIR motor is deliberately designed to minimize inrush current stress on small electrical circuits. However, never operate this compressor without refrigerant circulation, as the micro-displacement cannot provide adequate oil circulation for motor cooling without active refrigerant flow. Running dry for even 10 seconds risks motor winding insulation breakdown and bearing seizure.
Typical Installations:Countertop beverage coolers at gas stations (2–4°C setpoint), portable coolers for boats and RVs, laboratory equipment with temperature-sensitive components.
AKA9442EXD-R: 1/2 HP, 760 W Mid-Range R-22 and R-407C
The Tecumseh AKA9442EXD-R is a 1/2-horsepower, single-phase compressor rated for 760 W input power at ASHRAE conditions (20°F evaporation, R-22). This R-22 specialist bridges the gap between legacy CFC systems and modern HFC/HFO blends, making it particularly valuable for retrofit scenarios in regions where R-22 phase-out is gradual and drop-in R-407C migration is cost-justified.
R-22 vs. R-407C Power Characteristics:
The AKA9442EXD-R’s specification sheet documents 1,231 W refrigeration capacity @ 20°F evaporation on R-22 with 760 W input power, yielding a coefficient of performance (COP) of 1.62. When retrofitted to R-407C (a non-flammable synthetic blend approved as drop-in replacement for R-22), capacity typically increases by 5–10% while discharge temperature often remains within acceptable limits (usually 5–10°C lower than baseline R-22 operation).
Motor and Electrical Specs:
Motor Type: CSR (Capacitor-Start/Run) with HST winding
Locked-Rotor Amps: 31 A (moderate; 1/3 that of larger models)
Rated Load Amps: 4 A @ 60 Hz (very economical)
Max Continuous Current: 6.64 A (allows smaller circuit breakers)
Displacement: 15.634 cc (mid-range piston volume)
Application Sweet Spot:Deli display cases, pharmacy refrigerators, small ice makers, walk-in coolers 8–15 m³ (280–530 cu ft). The 0°F to 50°F (−17.8°C to 10°C) evaporating range covers both chilled fresh-food applications and moderately frozen goods.
AKA4476YXA-R: 3/4 HP, 1,070–1,111 W High-Temperature Retail Cooler
The Tecumseh AKA4476YXA-R is a 3/4-horsepower, single-phase compressor consuming 1,070–1,111 W input power across R-134a and R-513A refrigerants at 45°F evaporation (high back-pressure rating). This model is optimized for supermarket produce displays, dairy coolers, and retail beverage cases operating near 2–8°C (35–46°F) evaporating temperature, where high COP and low discharge temperature are essential for compressor longevity and energy efficiency.
R-134a vs. R-513A Performance:
Refrigerant
Input Watts
Capacity (W)
COP (W/W)
Pressure Class
R-134a
1,070 W
2,250 W
2.10
Standard HBP
R-513A
1,111 W
2,265 W
2.04
Higher pressure (HFO blend)
Electrical Characteristics:
Locked-Rotor Amps: 58.8 A (requires motor-protection relay and hard-start kit in marginal voltage conditions)
Rated Load Amps: 11.3 A @ 115 V 60 Hz (moderate continuous draw)
Displacement: 22.599 cc (larger than 1/2 HP models, smaller than 1 HP units)
Why High-Temperature Application? The 20°F to 55°F (−6.7°C to 12.8°C) evaporating range places this compressor in the HBP (High Back-Pressure) classification, meaning suction pressures remain elevated even at light loads, protecting the motor winding from low-temperature cooling inadequacy. This design philosophy prioritizes reliability at warm evaporating temperatures over capacity at low temperatures.
Typical Installations:Supermarket dairy sections, produce rooms, beverage coolers, medication storage (pharmacies), bakery cold cases. The high efficiency (COP ≈ 2.0) translates to lower energy bills compared to older R-22 compressors operating in equivalent service.
AWG5524EXN-S: 2 HP, 1,650–2,480 W Dual-Voltage Large-Displacement R-22
The Tecumseh AWG5524EXN-S is a 2-horsepower, single-phase (despite the three-phase-like capacity) compressor with input power ranging from 1,650 W (light load) to 2,480 W (full load) at varying condensing temperatures. This large-displacement unit (43.1 cc) ranks among Tecumseh’s largest reciprocating compressors, delivering approximately 7,091 W (24,200 BTU/h) refrigeration capacity on R-22 at full-load conditions.
Power Profile Across Operating Envelope (230 V single-phase, R-22):
Evaporating Temp.
Condensing Temp. 100°F
Condensing Temp. 110°F
Condensing Temp. 120°F
0°F
1,100 W input
1,070 W input
—
10°F
1,210 W input
1,190 W input
1,170 W input
20°F
1,520 W input
1,560 W input
1,600 W input
Motor and Electrical Specifications:
Motor Type: PSC (Permanent-Split-Capacitor) with LST (Low-Start-Torque)
Locked-Rotor Amps: 60 A (substantial; demands heavy-duty electrical infrastructure)
Rated Load Amps: 11 A @ 60 Hz (continuous draw; requires 15 A minimum breaker)
Max Continuous Current: 18.3 A (absolute maximum permissible)
Displacement: 43.1 cc (nearly twice that of 1 HP models)
LST Motor Advantage: Unlike HST (High-Start-Torque) designs used in smaller compressors, the AWG5524EXN’s LST motor intentionally reduces inrush-current stress on facility electrical switchgear, capacitors, and contactors. This soft-start characteristic is critical when retrofitting older air-conditioning systems where the existing electrical infrastructure is marginal.
Application Range:Large supermarket condensing units, commercial ice-cream machine rooms, warehouse-scale blast freezers, industrial process cooling, R-22 retrofit projects in high-tonnage systems. The −10°F to 55°F (−23.3°C to 12.8°C) evaporating range covers everything from low-temperature freezers to high-temperature AC conditioners, making this a true multi-temperature workhorse.
AKA4460YXD: 1/2 HP, 889–890 W High-Temperature R-134a Unit
The Tecumseh AKA4460YXD is a 1/2-horsepower, single-phase compressor drawing 889–890 W input power at high-temperature rating (R-134a, 45°F evaporation). Despite its modest 1/2 HP electrical rating, it delivers approximately 6,250 BTU/h (1,830 W) refrigeration capacity, making it highly efficient for retail cooler and air-conditioning applications where warm evaporating temperatures (20°F to 55°F) are the norm.
High-Temperature (HT) Performance Profile (115 V single-phase, R-134a):
Evaporating Temp.
Input Watts
Capacity (W)
Efficiency (W/W)
20°F
890 W
1,830 W
2.06
30°F
891 W
2,100 W
2.36
40°F
893 W
2,350 W
2.63
50°F
895 W
2,600 W
2.90
Exceptional Efficiency at Warm Operating Points: Notice that as evaporating temperature rises (warmer operating conditions), input wattage stays nearly constant (~890–895 W) while capacity increases dramatically (1,830 W → 2,600 W). This represents an efficiency gain from 2.06 to 2.90 W/W—a hallmark of HBP/high-temperature design.
Electrical Characteristics:
Motor Type: CSIR (Capacitor-Start/Induction-Run) with HST
Locked-Rotor Amps: ~50 A (requires start component verification)
Rated Load Amps: 4–5 A @ 115 V 60 Hz (lightweight; suitable for 20 A circuits)
Displacement: Similar to AKA9442EXD (~15 cc class)
Complementary vs. Competing Role: Where the AKA9442EXD-R is R-22 legacy-focused, the AKA4460YXD is R-134a modern-focused. Both offer 1/2 HP rating and similar electrical profiles, but the AKA4460YXD’s warm evaporating envelope makes it the choice for air-conditioning condensing units and warm-weather cooler applications, while AKA9442EXD-R excels at chilled/frozen food storage.
Comparative Wattage and Efficiency Analysis
Power-to-Capacity Ratio (Input Watts vs. Refrigeration Watts)
To understand compressor efficiency relative to cooling output, the power-to-capacity ratio (also called COP or W/W coefficient) reveals which models deliver the most cooling per watt of electrical input:
Model
HP
Input Watts
Cooling Watts
W/W Ratio
Efficiency Ranking
AKA4460YXD
1/2
890
1,830–2,600
2.06–2.90
Excellent (HT-optimized)
AKA4476YXA-R
3/4
1,070
2,250
2.10
Excellent (HT-optimized)
AWG5524EXN-S
2
1,650–2,480
7,091
2.86 (avg)
Very Good
AKA9438ZXA
1/2
756
1,099
1.45
Good (CBP-rated)
AKA9442EXD-R
1/2
760
1,231
1.62
Good
AZA0395YXA
1/9
230
278
1.21
Fair (micro-sized)
AVA7524ZXT
3
3,490–4,000
6,973
1.74–1.99
Good
AWA2460ZXT
1.5
1,552–1,686
1,758
1.04–1.13
Fair (LT-rated; high pressure)
AHA2445AXD
1
1,225
1,289
1.05
Fair (legacy; low efficiency)
Key Insight:High-temperature (HT) models (AKA4460YXD, AKA4476YXA-R) deliver 2.0–2.9 W/W efficiency because warm evaporating temperatures reduce compression pressure ratios, allowing smaller volumes of gas to do more cooling work. Conversely, low-temperature (LT) models like AWA2460ZXT and AHA2445AXD struggle to exceed 1.1 W/W because extreme temperature differentials force large compression ratios with inherent inefficiency.
Refrigerant Selection and Wattage Impact
How Refrigerant Changes Input Power Requirements
The same compressor model can consume different input wattage depending on refrigerant choice. The AVA7524ZXT at 20°F evaporation is a perfect case study:
Refrigerant
Input Watts
Vs. R404A
Discharge Temp.
Pressure Ratio
R404A
4,000 W
Baseline (highest)
95°C (typical)
8.5:1
R449A
3,622 W
−9.4%
85°C (lower)
8.1:1
R448A
3,622 W
−9.4%
85°C (lower)
8.1:1
R452A
3,772 W
−5.7%
88°C
8.3:1
R407A
3,490 W
−12.8%
78°C (lowest)
7.9:1
R407A is the most efficient (3,490 W input) because it has a lower volumetric expansion ratio and inherently lower discharge temperatures. However, R407A is being phased down in favor of low-GWP blends like R448A and R452A, which offer 10–15°C lower discharge temperatures compared to baseline R404A while maintaining similar electrical input (within ±10%).
Installation, Electrical Integration, and Safety Guidelines
Matching Electrical Infrastructure to Compressor Power Draw
A critical installation error is undersizing circuit protection or motor starters relative to compressor inrush current. Example scenario:
Site Condition: Installation of AKA9438ZXA (1/2 HP, 756 W input) into a facility with existing 15 A circuit breaker.
Problem:Locked-rotor amps = 58.8 A. The motor starting relay must energize the compressor, causing inrush current of 58.8 A for ~200 ms. A 15 A breaker trips immediately; a 20 A breaker may nuisance-trip if voltage sags during startup.
Solution: Install hard-start kit (start capacitor 30–45 µF + potential relay) to reduce effective locked-rotor current to 30–40 A, allowing a 20 A breaker to handle the inrush safely.
Three-Phase vs. Single-Phase Considerations
Three-Phase Models (AVA7524ZXT, AWA2460ZXT):
Advantage: Much lower inrush current per phase (typically 1/3 of single-phase equivalent)
Disadvantage: Requires three-phase electrical service; facility must have three separate 120° phase waveforms
Advantage: 115 V or 208–230 V single-phase service available at nearly every site
Disadvantage: High inrush current (50–60 A); requires robust start components and voltage-stable circuits
Typical Sites: Retail stores, restaurants, small convenience shops
Voltage Sensitivity: All compressors are sensitive to ±10% voltage variation. A 115 V compressor operating at only 103.5 V (10% sag) experiences reduced motor torque, slower startup, and risk of thermal overload. Facilities with chronic voltage sag must install voltage-stabilizing transformers or power-factor correction equipment.
Complete Tecumseh compressor technical data: exact horsepower (1/9 HP to 3 HP), input watts (230 W to 4,000 W), R404A R134a capacities, and application guide for every model.
Tecumseh commercial compressors range from 1/9 HP (230 W) to 3 HP (4,000 W), delivering refrigeration capacities from 278 W to 6,973 W across R404A, R134a, and legacy refrigerants. This complete technical guide provides exact horsepower, input wattage, evaporating ranges, and application types for all ten major models used in supermarkets, walk-ins, and retail coolers.
The Cold Heart of Commercial Freezing: Embraco NEU2178GK
If you are an artisan bricoleur or a refrigeration technician working on commercial island freezers or restaurant reach-ins, you have likely encountered the Embraco NEU2178GK. This isn’t your standard domestic fridge compressor; this is a 1 HP powerhouse designed for the heavy lifting required by Low Back Pressure (LBP) applications using R404A or R507 refrigerant.
Known for its robust “Made in Slovakia” build, the NEU2178GK is a CSR (Capacitor Start, Capacitor Run) motor. This is a critical detail for technicians: unlike simpler PTCSCR compressors, this unit relies on a precise electrical box containing both a start capacitor and a run capacitor to manage its high starting torque (HST). It is the engine you choose when you need reliability in a -30°C environment.
Why the “GK” Matters
In Embraco’s nomenclature, the “K” at the end (as in NEU2178GK) often signifies a specific motor type—in this case, one designed for High Starting Torque. This means it can restart even if pressures haven’t fully equalized, a common scenario in busy commercial kitchens where doors are opened frequently.
Technical Specifications: The Data You Need
Here is the breakdown of the technical capabilities of this compressor.
Feature
Specification
Model
NEU2178GK
Brand
Embraco (Nidec)
Horsepower (HP)
1 HP
Displacement
16.80 cm³ (cc)
Refrigerant
R404A / R507 / R452A
Application
LBP (Low Back Pressure)
Voltage
220-240V ~ 50Hz
Cooling Capacity
~900 W (at -23.3°C ASHRAE)
Motor Type
CSR (Capacitor Start & Run)
Start Capacitor
88 – 108 µF / 330V
Run Capacitor
15 µF / 400V
Oil Type
POE 22 (Polyolester)
Oil Charge
350 ml
Expansion Device
Capillary or TXV (Expansion Valve)
Exploitation: Installation Tips for the Artisan
Installing a 1 HP commercial compressor is different from swapping a domestic one. Here are the “golden rules” for the NEU2178GK:
The Electric Box is Mandatory: You cannot bypass the capacitor box. This motor needs the 15µF run capacitor to maintain efficiency and keep the windings cool, and the start capacitor to kick the rotor into motion against high head pressure.
Moisture is the Enemy: This compressor comes filled with POE oil. POE is like a sponge for humidity. If you leave the plugs open for more than 15 minutes, the oil absorbs moisture that vacuum pumps cannot remove. Keep it sealed until the last second.
Nitrogen Sweep: Because R404A systems use POE oil, any carbon from brazing will turn into sludge and block the capillary tube immediately. Always braze with a trickle of nitrogen flowing through the pipes.
R452A Compatibility: If R404A is expensive or restricted in your area, this compressor is often compatible with R452A, a drop-in replacement with a lower GWP (Global Warming Potential), but always check the discharge temperature.
Comparison: Embraco NEU2178GK vs. The Competition
When you can’t find the exact Embraco model, you need a replacement. Here is how it stacks up against the heavyweights from Secop and Tecumseh.
Compressor
Brand
Approx. HP
Displacement
Verdict
NEU2178GK
Embraco
1 HP
16.8 cc
Best for high-torque commercial freezers.
SC21CL
Secop (Danfoss)
~7/8 – 1 HP
20.95 cc
Older design, physically larger, very reliable.
CAJ2464Z
Tecumseh
1.5 HP
34.4 cc
Much more powerful; usually overkill for this slot.
NT2180GK
Embraco
1 HP
20.4 cc
The “big brother” of the NEU series; fits if you have space.
Pro Tip: If replacing a Secop SC21CL with this Embraco NEU2178GK, you may need to adjust the pipework as the Embraco is slightly more compact (lower height: ~206mm vs Secop ~219mm).
Performance Analysis: Power Consumption
One reason technicians love the NEU series is efficiency.
Current (Amps): At typical freezer conditions (-25°C), it draws about 4.3 Amps.
LRA (Locked Rotor Amps): 21.0 A. If your clamp meter reads 21A instantly and stays there, your compressor is mechanically seized or the start capacitor is dead.
Performance Analysis: Power Consumption
One reason technicians love the NEU series is efficiency.
Current (Amps): At typical freezer conditions (-25°C), it draws about 4.3 Amps.
LRA (Locked Rotor Amps): 21.0 A. If your clamp meter reads 21A instantly and stays there, your compressor is mechanically seized or the start capacitor is dead.
Focus Keyphrase: Embraco NEU2178GK 1 HP Compressor R404A
Meta Description: Discover the Embraco NEU2178GK 1 HP Compressor (R404A/LBP). Full technical specs, CSR wiring guide, and comparisons with Secop and Tecumseh for commercial refrigeration repairs.
Excerpt: The Embraco NEU2178GK is the definitive choice for 1 HP commercial freezing applications. Featuring a robust CSR motor and 16.8cc displacement, this R404A compressor delivers high starting torque for demanding environments. This guide details the electrical requirements, installation tips, and how it compares to Secop and Tecumseh alternatives.
Copeland ZB50KCE Scroll Compressor Nameplate: How to Read the Label and Choose the Right Polyester Oil
The photo shows the damaged nameplate of a Copeland ZB50KCE scroll compressor, factory‑charged with polyester (POE) oil for medium‑temperature refrigeration. Correctly interpreting this label helps technicians confirm oil, power, voltage and safety limits during service or replacement.
Compressor identification
The model belongs to the Copeland ZB series, used in commercial cold rooms and process cooling for refrigerants such as R404A, R134a and R22 alternatives. Depending on voltage code (TFD‑551, TFD‑950, etc.), it is sold as a 7 hp medium‑temperature compressor with around 11.9 kW nominal capacity.
Model code example: ZB50KCE‑TFD‑551 or ZB50KCE‑TFD‑950.
Technology: Hermetic scroll, part of the Summit series designed for higher seasonal efficiency.
Polyester oil (POE) on the label
The upper part of the label still shows POLYESTER OIL, confirming that the compressor is charged with POE lubricant. Catalogues list oil charges of about 2.6–2.7 l using approved POE types such as RL32‑3MAF or Mobil EAL Arctic 22 CC, depending on the variant.
POE oil absorbs moisture quickly, so systems must be evacuated deeply and fitted with quality filter‑driers.
Only compatible POE grades should be added; mixing with mineral or alkylbenzene oil is not permitted.
Technical data with hp and W
The following table compiles typical data for a Copeland ZB50KCE‑TFD‑551 running as a medium‑temperature refrigeration compressor; values may vary slightly by refrigerant and exact model.
Parameter
Typical value for ZB50KCE*
Nominal power
7 hp
Nominal capacity
11.9 kW cooling (≈11 900 W)
Electrical power input
≈7.5–7.9 kW depending on conditions
Displacement
19.8 m³/h
Supply voltage
380–420 V/3/50 Hz and 460 V/3/60 Hz (TFD code)
Maximum operating current
14.6 A
Locked‑rotor current
≈100 A
Oil type
POE (e.g. RL32‑3MAF)
Oil quantity
2.6–2.7 l
Sound level
≈64 dBA at 1 m
Net weight
≈59 kg (TFD‑551)
*Always confirm with the exact data sheet for your compressor code.
Voltage and operating limits on the sticker
On the lower part of the photographed label, remnants of “Volt 1 380 … Volt 2 460” can be identified, matching the dual‑voltage three‑phase motor used in TFD models. Another line mentions maximum current around 14.6 A, which is the value used to size breakers, contactors and cables.
The TFD motor code indicates 380–420 V/3/50 Hz and 460 V/3/60 Hz with internal motor protection.
Respecting these limits and using proper overload protection prevents overheating and nuisance trips in commercial installations.
Practical maintenance notes
For technicians such as those in Mbsmgroup and Mbsm.pro, a faded nameplate is common on older units, but the combination of model code and official catalogue restores all critical information. Creating a new service label with hp, kW, voltage, POE oil type and charge simplifies future troubleshooting and reduces the risk of mistakes during oil changes or retrofits.
When replacing or topping up oil, always isolate the compressor, recover refrigerant and work under clean, dry conditions.
If in doubt about capacity or application limits, refer to the Copeland ZB range catalogue and selection software before approving a replacement.
Refrigerants, Standing, Suction and Discharge Pressures for Modern HVAC Systems
Category: Refrigeration
written by www.mbsmpro.com | January 26, 2026
Guide to Common Refrigerants: Standing, Suction and Discharge Pressures for Modern HVAC Systems
Refrigeration technicians today work with a mix of legacy and new-generation refrigerants, each with its own safe pressure range and boiling temperature. Understanding these values is essential for accurate diagnostics, safe charging and long compressor life in air‑conditioning and commercial refrigeration.
Key role of pressure charts
Pressure–temperature charts and standing/suction/discharge tables give technicians a fast reference for what a system “should” be doing at a given ambient or evaporating temperature. Using wrong reference values can lead to over‑charging, overheating, liquid slugging or misdiagnosis of a healthy system as faulty.
Overview of common refrigerants
The image groups the most used refrigerants in residential and light commercial systems: R22, R134a, R600a, R32, R290, R407C, R404A, R410A and R417 (R417A). Each gas has a typical standing pressure (static pressure at rest), an evaporating suction pressure, a condensing discharge pressure and a characteristic boiling point at atmospheric pressure.
Typical pressure ranges from the chart
The following table summarises the indicative values shown in the chart (all pressures are approximate, for normally loaded systems at typical comfort‑cooling conditions).
Indicative pressures and boiling points
Refrigerant
Approx. standing pressure
Approx. suction pressure
Approx. discharge pressure
Boiling point (°C)
Typical replacement for
R22
150–155 psi / 1034–1069 kPa
60–70 psi / 413–483 kPa
250–300 psi / 1724–2069 kPa
−40.8 °C
R11 / legacy R22 AC
R134a
80–95 psi / 552–655 kPa
12–15 psi / 83–103 kPa
~150 psi / 1034 kPa
−26.2 °C
R12 in domestic & auto
R600a
40–50 psi / 276–345 kPa
≈0–1 psi / 0–7 kPa
~150 psi / 1034 kPa
−11.7 °C
Low‑charge fridges, R12
R32
240–245 psi / 1655–1689 kPa
110–115 psi / 758–793 kPa
175–375 psi / 1207–2586 kPa
−52.0 °C
High‑efficiency R410A/R22
R290
125–130 psi / 862–896 kPa
65–70 psi / 448–483 kPa
275–300 psi / 1896–2069 kPa
−42.1 °C
R22 in some systems
R407C
180–185 psi / 1241–1276 kPa
75–80 psi / 517–552 kPa
275–300 psi / 1896–2069 kPa
−45.0 °C (bubble)
R22 retrofits
R404A
180–185 psi / 1241–1276 kPa
80–90 psi / 552–621 kPa
275–300 psi / 1896–2069 kPa
−46.2 °C
R502 low‑temp systems
R410A
225–230 psi / 1551–1586 kPa
120–130 psi / 828–896 kPa
450–500 psi / 3103–3447 kPa
−51.4 °C
Modern R22 AC
R417A
~140 psi / 965 kPa standing
~65 psi / 448 kPa suction
~261 psi / 1796 kPa discharge
−39.0 °C
R22 service blend
These figures are not universal “set‑points”, but practical targets that help technicians decide whether a system is under‑charged, over‑charged or suffering airflow or mechanical problems.
Safety, cylinder colours and replacements
Many countries use conventional cylinder colour codes to identify refrigerants quickly on site, although some regions are migrating to neutral colours with clear labelling. Hydrocarbons such as R290 and R600a are flammable, so working pressures must always be combined with strict leak‑prevention, ventilation and ignition‑control procedures.
When phasing out ozone‑depleting R22, blends like R407C or R417A are often used in retrofit projects, while new high‑efficiency equipment typically relies on R410A or R32 with different design pressures. Comparing the standing and operating pressures during commissioning helps ensure that a replacement refrigerant is compatible with existing components such as compressors, valves and heat‑exchangers.
Practical use for technicians and trainers
Technicians can laminate similar tables and keep them in the toolbox or on the workshop wall as a quick‑reference during charging and troubleshooting.
Training centres and HVAC content creators like Mbsmgroup and Mbsm.pro can turn these values into interactive quizzes, infographics or mobile‑friendly charts for students and new technicians.
