Lennox ML17XC1 Series Outdoor Air Conditioner
Service Literature - Unit Information
Date: June 22, 2023
General Information
⚠️ WARNING: Improper installation, adjustment, alteration, service or maintenance can cause property damage, personal injury or loss of life. Installation and service must be performed by a licensed professional HVAC installer or equivalent, service agency, or the gas supplier.
❗ CAUTION: As with any mechanical equipment, contact with sharp sheet metal edges can result in personal injury. Take care while handling this equipment and wear gloves and protective clothing.
⚠️ WARNING: Electric Shock Hazard. Can cause injury or death. Unit must be properly grounded in accordance with national and local codes. Line voltage is present at all components when unit is not in operation on units with single-pole contactors. Disconnect all remote electric power supplies before opening access panel. Unit may have multiple power supplies.
⚠️ WARNING: To prevent serious injury or death: 1. Lock-out/tag-out before performing maintenance. 2. If system power is required, disable power to blower, remove fan belt where applicable, and ensure all controllers and thermostats are set to the “OFF” position before performing maintenance. 3. Always keep hands, hair, clothing, jewelry, tools, etc. away from moving parts.
ℹ️ IMPORTANT: This unit must be matched with an indoor coil as specified with AHRI. For AHRI Certified system match-ups and expanded ratings, visit www.LennoxPros.com. Coils previously charged with HCFC-22 must be flushed.
This ML17XC1 outdoor air conditioner with all-aluminum coil is designed for use with HFC-410A refrigerant only. It must be installed with an approved indoor air handler or coil. Consult authorities having jurisdiction before installation. This outdoor unit is designed for systems using a Thermal Expansion Valve (TXV) or a Fixed orifice metering device.
ℹ️ IMPORTANT: Special procedures are required for cleaning the aluminum coil. See page 25 for information.
Model Number Identification
The model number ML17XC1-036-230A01 breaks down as follows:
- Product Tier: ML = Merit® Series
- Nominal SEER2: 17
- Refrigerant Type: X = R-410A
- Unit Type: C = Air Conditioner (Condenser)
- Cooling Stages: 1 = Single Stage Compressor
- Voltage: 230 = 208/230V - 1 phase - 60Hz
- Nominal Cooling Capacity: Examples include 018 (1.5 tons) through 060 (5 tons).
Typical Serial Number Identification
Serial numbers indicate manufacturing details:
Example: 58 21 C 05716
- Location Code: 58 = Marshalltown, IA
- Year Code: 21 = 2021
- Month Code: C = March
- Unique Number: 05716
Specifications
The ML17XC1 series offers various models with detailed specifications:
| General Data | ML17XC1-018 | ML17XC1-024 | ML17XC1-030 | ML17XC1-036 | ML17XC1-041 |
|---|---|---|---|---|---|
| Nominal Tonnage | 1.5 | 2 | 2.5 | 3 | 3.5 |
| Liquid line o.d. - in. (sweat) | 3/8 | 3/8 | 3/8 | 3/8 | 3/8 |
| Suction line o.d. - in. | 3/4 | 3/4 | 3/4 | 7/8 | 7/8 |
| Refrigerant (R-410A) furnished | 4 lbs. 8 oz. | 5 lbs. 2 oz. | 6 lbs. 8 oz. | 8 lbs. 8 oz. | 8 lbs. 12 oz. |
| Outdoor Coil Net face area sq. ft. | 16.33 | 21.00 | 16.33 | 21.00 | 22.17 |
| Outdoor Fan Motor hp | 1/6 | 1/8 | 1/8 | 1/6 | 1/3 |
| ELECTRICAL DATA: Max OCP amps | 15 | 20 | 25 | 30 | 35 |
Full specifications including dimensions, electrical data, and optional accessories are detailed in the original document.
Unit Dimensions
Dimensions (A, B, C) in inches and millimeters are provided for each model.
| Model | A (inches / mm) | B (inches / mm) | C (inches / mm) |
|---|---|---|---|
| 018 | 28-1/4 / 718 | 29-1/4 / 743 | 28-1/2 / 724 |
| 024 | 28-1/4 / 718 | 37-1/4 / 946 | 36-1/2 / 927 |
| 030 | 28-1/4 / 718 | 29-1/4 / 743 | 28-1/2 / 724 |
| 036 | 28-1/4 / 718 | 37-1/4 / 946 | 36-1/2 / 927 |
| 041 | 32-1/4 / 819 | 33-1/4 / 845 | 32-1/2 / 927 |
| 042 | 32-1/4 / 819 | 33-1/4 / 845 | 32-1/2 / 826 |
| 047 | 32-1/4 / 819 | 33-1/4 / 845 | 32-1/2 / 826 |
| 048 | 28-1/4 / 718 | 43-1/4 / 1099 | 42-1/2 / 1080 |
| 059 | 32-1/4 / 819 | 43-1/4 / 1099 | 42-1/2 / 1080 |
| 060 | 32-1/4 / 819 | 43-1/4 / 1099 | 42-1/2 / 1080 |
Figure 4 illustrates placement and slab mounting details.
Typical Unit Parts Arrangement
Figure 1 shows the typical internal components, including the control box, compressor, high pressure switch, and service valves.
Component Specifications
Key component specifications include:
- Service Valve Sizes & Line Set Recommendations: Details on liquid/suction line sizes and recommended line sets (L15 Series).
- Fixed Orifice (RFC) Metering: Table 2 lists orifice sizes required for specific outdoor units.
- Expansion Valve (TXV) Metering: Unit is compatible with TXV systems.
- Torque Requirements: Table 3 specifies torque values for various fasteners like service valve caps, machine screws, and compressor bolts.
- Manifold Gauge Set: Requirements for HFC-410A systems are outlined.
- Service Valves: Information on Angle and Ball type service valves is provided.
Installation
Proper installation is critical for unit performance and safety. Key steps and considerations include:
Unit Placement
Considerations for unit placement include sound ordinances, proximity to windows, and slab/roof mounting. Units should be installed on a level surface or with a slight slope tolerance. Roof installations require a minimum clearance of 6 inches (152 mm) above the roof surface. Clearances around the unit are specified in Figure 3 to ensure proper airflow and service access.
Removing and Installing Louvered Panels
Figure 5 provides a step-by-step guide for removing and reinstalling the unit's access panels (Panels A, B, C, D).
New or Replacement Line Set
Table 4 specifies recommended line set sizes (liquid and suction lines) for different models, including L15 Series and field-fabricated options. Proper line set insulation is important, especially when ambient temperatures may exceed liquid line temperature.
Brazing Connections
Figures 8 and 9 detail the brazing procedures for connecting line sets to service valves. ⚠️ WARNING: Danger of fire exists if system is pressurized and heat is applied. Use appropriate silver alloy brazing rods (5% silver for copper-to-copper, 45% for copper-to-brass/steel). ❗ CAUTION: Brazing alloys and flux can be hazardous; use in well-ventilated areas with protective gear. ℹ️ IMPORTANT: Allow braze joints to cool to prevent damage to valve seals. If the unit is matched with a system previously charged with mineral oil, the coil and line set must be flushed.
Flushing Line Set and Indoor Coil
Figure 10 outlines procedures for flushing the line set and indoor coil, using clean HCFC-22 refrigerant, to remove contaminants, especially when switching from mineral oil to POE oil systems.
Installing Indoor Metering Device
Figure 11 details the installation of the indoor expansion valve (TXV) or fixed orifice (RFC) metering device, including sensing bulb and equalizer line connections.
Leak Testing the System
Figure 12 describes the procedure for leak testing the line set and indoor coil using nitrogen. A leak detector capable of sensing HFC refrigerant is required.
Evacuating Line Set and Indoor Coil
Figure 13 details the process of evacuating the system to remove non-condensables and moisture, using a vacuum pump and micron gauge to achieve specified vacuum levels (e.g., 500 microns).
Electrical - Circuit Sizing and Wire Routing
Wiring must comply with National Electric Code (NEC) and Canadian Electrical Code (CEC). Use only copper conductors. Ensure proper circuit sizing and disconnect switch installation. A 24VAC transformer is used for control power. ⚠️ WARNING: Aluminum wire poses a fire hazard; use copper wire only.
Figure 14 illustrates typical high voltage, ground, and control wiring. Figures 15, 16, 17, and 18 show specific factory wiring diagrams for different unit configurations.
Thermostat Installation
Install thermostat on an inside wall, approximately centered in the conditioned area, 5 feet (1.5m) from the floor, away from direct sunlight or drafts.
System Operation
The outdoor unit and indoor blower cycle based on thermostat demand. The High Pressure Switch (S4) protects the compressor by cutting power if discharge pressure exceeds a set limit. Crankcase heaters (HR1) prevent liquid refrigerant accumulation in the compressor, controlled by thermostat (S40).
Maintenance
Annual inspection and maintenance by a licensed HVAC technician is recommended. Key checks include:
- Outdoor Unit: Inspect wiring, fan/blades, drain pans, refrigerant piping, capacitors, contactors, and coils.
- Indoor Unit: Inspect wiring, air filters, blower, evaporator coil, drain pans, and refrigerant lines.
ℹ️ NOTICE: Aluminum coils may be damaged by solutions with pH below 5 or above 9. Clean with potable water or a pH-neutral cleaner (pH 5-9) and rinse thoroughly. In coastal areas, clean coils with potable water several times per year to prevent salt buildup.
Start-Up and Performance Checklist
A general system test should be performed by a technician to check operating functions, noises, odors, temperatures, and pressures. The checklist includes verifying electrical connections, filter cleanliness, airflow, refrigerant charge, and thermostat settings.
System Refrigerant
Procedures for connecting gauge sets, checking/adjusting airflow (Delta-T method), and adding/removing refrigerant (HFC-410A) are detailed. Charge methods (Approach TXV, Subcooling TXV, Weigh-in RFC) are described, referencing various tables for pressures, temperatures, and superheat/subcooling values.
