Installation: Lennox Industries 508873-01 Natural to LP Gas Changeover Kit Instruction Manual

Content

Overview

The 508873-01 Natural to LP Gas Changeover Kit converts compatible Lennox LG/LD 024–074 packaged rooftop units from natural gas to LP (propane) gas. It is intended for qualified service agencies and licensed professional installers who can perform gas-appliance conversion, electrical isolation, pressure verification, combustion checks, and leak testing.

The kit changes the burner orifices, configures the applicable gas valve, and adds a combustion-air blower harness. The converted unit must be tested and adjusted according to the unit rating plate and the installation instructions before being placed into service.

Specifications

Kit number: 508873-01
Application: LG/LD 024–074 packaged rooftop units
Conversion: Natural gas to LP/propane gas
Applicable unit categories: LG/LD 024-074S/H/U
Related kit assembly 39H78: part number 614839-11
Related kit assembly 39H79: part number 614839-12
Gas valve identification: the tenth character of the unit model number identifies the valve and heating configuration
Valve types covered: White-Rodgers 36J54 two-stage and 36J27 modulating valves
Burner quantity: units may contain three, five, or seven burners
Manifold pressure units: inches water column, with kilopascal equivalents shown on the unit documentation
High-altitude range addressed: above 2,000 feet, with regional limits and adjustments determined by the installation location

Package Contents

The 508873-01 Natural to LP Gas Changeover Kit is supplied as one package containing the parts required for the conversion.

Seven LP burner orifices, supplied with the 39H79 assembly
Spring kit for applicable 36J54 two-stage gas valves
Jumper kit for applicable 36J27 modulating gas valves
J/P21 harness
Pressure tubing kit
Installation instructions
Dealer conversion label
Conversion plate

Use only the orifices required for burners actually installed in the unit. Do not install unused orifices in empty burner positions.

Detailed Description

LP gas requires different burner metering and gas-valve configuration than natural gas. The conversion kit supplies replacement orifices sized for LP operation and the components needed to configure the unit’s gas valve.

On two-stage units using a White-Rodgers 36J54 combination valve, the dedicated spring kit changes the valve configuration for LP operation. On modulating units using a White-Rodgers 36J27 valve, the dedicated jumper kit provides the required valve configuration. The kit also connects the combustion air blower through the J/P21 harness so the converted heating system can operate with the appropriate control arrangement.

The gas valve type and heating arrangement must be confirmed from the unit model information before installation. For example, the tenth model-number character identifies the gas-valve configuration used by the unit.

Safety

Installation must be performed by a qualified service agency familiar with gas equipment and local requirements. Improper installation, adjustment, alteration, service, or maintenance can cause fire, explosion, carbon monoxide production, property damage, serious injury, or death.

Follow the unit and kit instructions exactly.
Comply with all applicable codes and requirements of the authority having jurisdiction.
Canadian installations must comply with the applicable provincial requirements and CAN/CGA-B149.1 and CAN/CGA-B149.2 installation codes.
Turn off electrical power at the disconnect before service. Packaged rooftop units may have more than one power supply.
Use caution around sheet-metal edges and internal components.
Never use the kit to convert a unit that has been under water. A qualified technician must inspect the appliance and replace affected controls and gas-control components.
If overheating occurs or the gas supply does not shut off, close the manual gas valve before disconnecting electrical power.
Do not attempt to light the burners manually. The unit uses direct spark ignition and has no standing pilot.
If gas is smelled, stop work, avoid ignition sources, and follow the gas supplier’s emergency instructions.

Installation

Prepare the Unit

Close the gas supply to the rooftop unit.
Set the thermostat to its lowest setting or to Off.
Switch off all electrical power to the unit.
Open the compressor access panel and the blower/heat access panel.
Remove the mullion between the two open access panels and retain the hardware.

Replace the Burner Orifices

Remove and retain the four screws securing the manifold to the burner box.
Remove the manifold to expose the installed orifices.
Remove the existing natural-gas orifices.
Install the LP orifices supplied with the kit only where a burner is installed. Depending on the unit, three, five, or seven burner positions may be used.
Tighten pipe-threaded orifices to 6.25 ft-lb.
Do not overtighten the orifices.
Do not apply thread compound to gas orifices.
Reinstall the manifold and secure it with the retained screws.

Configure the Gas Valve

Match the conversion component to the gas valve installed in the unit.

36J54 two-stage valve: Use the spring kit labeled with manufacturer part number F92-1008. Follow the spring-kit instructions for installing the spring components and LP labels.
36J27 modulating valve: Use the jumper kit labeled with manufacturer part number F92-1021. Follow the kit instructions for installing the jumper plug and LP labels.

Do not substitute the spring kit for a modulating valve or the jumper kit for a two-stage valve.

Install the J/P21 Harness

Locate the combustion air blower in the heating section.
Disconnect the blower motor’s four-position plug from the unit’s four-position jack.
Confirm the correct connection by checking for the P442-P19 identification stamped on the unit-side wiring.
Install the supplied harness between the blower motor plug and the unit jack.
Reconnect and route the harness so it is protected from sharp edges, moving components, and excessive heat.

Complete the Mechanical Installation

Inspect the manifold, burner area, wiring, and harness connections.
Reinstall the mullion between the compressor access and blower/heat access panels.
Replace the access panels before restoring operation.
Complete the start-up, pressure checks, high-altitude adjustments, and leak checks described below.

Startup and Operation

Before Lighting

Before starting the unit, smell around the appliance and near the floor for gas because LP vapor can settle in low areas. The gas valve switch or control knob must be operated by hand only. Do not force a control that will not move.

Set the thermostat to its lowest setting.
Turn off electrical power to the appliance.
Open or remove the control access panel.
Move the gas-valve switch to Off.
Wait five minutes to allow any accumulated gas to disperse.
If gas is still detected, stop and contact the gas supplier through an appropriate safe method.
If no gas is detected, move the gas-valve switch to On.
Close or replace the control access panel.
Restore electrical power.
Set the thermostat to the desired heating setting.

The direct-spark ignition sequence starts automatically. During initial startup, the procedure may need to be repeated to purge air from the gas line. If ignition does not occur, the unit can make up to two additional ignition attempts before locking out. After a lockout, repeat the startup sequence. If the unit still will not operate, turn off the gas as described below and have the appliance inspected by a qualified service technician.

Turn Off the Gas

Set an electromechanical thermostat to its lowest setting, if applicable.
Turn off all electrical power before service.
Open or remove the control access panel.
Move the gas-valve switch to Off.
Close or replace the control access panel.

Gas Heating Checks and Adjustments

Verify Gas Flow

Use the heating input shown on the unit rating plate. Divide the input in Btu per hour by the heating value of the available gas in Btu per cubic foot to calculate the required gas flow in cubic feet per hour. To check the meter, measure the gas used during two minutes and multiply that result by 30.

Check Supply Pressure

Check supply pressure while the unit operates at maximum input. LP supply pressure must remain within the minimum and maximum values specified on the unit rating plate. On installations with multiple units, check each unit separately both with the other units operating and with them off.

Measure Supply Pressure

Close the field-supplied manual main gas valve before installing or removing a measuring device.
For a White-Rodgers 36J54 valve, remove the 1/8-inch hex screw, install a suitable 1/8-inch fitting with hose barb, and connect tubing to the measuring instrument.
For a White-Rodgers 36J27 valve, locate the 5/16-inch inlet pressure post. Turn the pressure-tap screw one rotation counterclockwise with a 3/32-inch hex wrench, then place 5/16-inch inside-diameter tubing over the post.
Open the manual gas valve and ignite the unit.
Allow the unit to operate for five minutes to reach steady conditions.
Record the supply pressure and compare it with the unit rating-plate requirements.
Shut the unit off and remove the measuring equipment.
On a 36J54 valve, reinstall the 1/8-inch hex screw. On a 36J27 valve, remove the tubing and turn the pressure-tap screw clockwise to seal the port.

Measure and Adjust Manifold Pressure

Close the manual main gas valve before installing or removing the measuring device.
For a 36J54 valve, remove the manifold-pressure 1/8-inch hex screw, install an appropriate fitting with hose barb, and connect the hose to the positive side of the measuring device.
For a 36J27 valve, turn the manifold-pressure tap screw one rotation counterclockwise with a 3/32-inch hex wrench and connect 5/16-inch inside-diameter tubing to the pressure post.
Open the gas valve and ignite the unit.
Allow five minutes for steady operation. If the unit has two heating inputs, begin with the higher input.
Record manifold pressure and compare it with the unit nameplate values.
Adjust manifold pressure when required using the adjustment locations shown for the installed gas valve.
Repeat the measurement and adjustment for the lower input.
Turn off the unit and remove the measuring equipment.
Reseal the pressure port. Reinstall the 1/8-inch screw on a 36J54 valve or turn the 36J27 manifold-pressure tap screw clockwise after removing the tubing.
Restart the unit and perform a gas-leak check. Correct any leak before placing the unit into service.

High-Altitude Adjustment

Units may operate at full input up to 2,000 feet above sea level. Above that elevation, manifold pressure and heating input require adjustment.

In the United States, reduce heating input by 2 percent for each 1,000 feet above sea level, following the applicable LP pressure table and local requirements.
In Canada, local authorities determine certification requirements above 4,500 feet. The recommended reduction is 2 percent for each additional 1,000 feet above 4,500 feet.
For fuel heating values above 2,500 Btu per cubic foot, verify the reduced input using the local heating value and the gas-flow procedure.

LP Manifold Pressure Reference

The following values are the LP manifold-pressure values provided for the two heating input ranges. Confirm the correct regional table and unit configuration before adjustment.

Region and altitude	Low input	High input
United States or Canada, 0–2,000 ft	5.9 in. w.c. (1.47 kPa)	10.5 in. w.c. (2.62 kPa)
United States or Canada, 2,001–4,500 ft	5.1 in. w.c. (1.27 kPa)	9.0 in. w.c. (2.24 kPa)
Canada, 4,501–5,500 ft	4.8 in. w.c. (1.20 kPa)	8.5 in. w.c. (2.12 kPa)
Canada, 5,501–6,500 ft	4.5 in. w.c. (1.12 kPa)	8.1 in. w.c. (2.02 kPa)
Canada, 6,501–7,500 ft	4.4 in. w.c. (1.10 kPa)	7.8 in. w.c. (1.94 kPa)
United States, 4,501–5,000 ft	5.1 in. w.c. (1.27 kPa)	9.0 in. w.c. (2.24 kPa)
United States, 5,001–6,000 ft	4.8 in. w.c. (1.20 kPa)	8.5 in. w.c. (2.12 kPa)
United States, 6,001–7,000 ft	4.5 in. w.c. (1.12 kPa)	8.1 in. w.c. (2.02 kPa)
United States, 7,001–8,000 ft	4.4 in. w.c. (1.10 kPa)	7.8 in. w.c. (1.94 kPa)

Identify the Converted Unit

Find the LP conversion label showing the kit number and heater input size.
Place the label near the unit nameplate.
Complete the installer conversion label.
Affix the completed label near the nameplate so future service personnel can identify the LP conversion.

Troubleshooting

Burner does not ignite: Verify that the gas supply is open, the gas valve is set to On, electrical power is restored, and the gas line has been purged. Do not attempt manual ignition.
Unit locks out during startup: Repeat the complete startup procedure. The ignition control may make up to three total attempts when air remains in the gas line.
Gas pressure is outside the specified range: Stop operation and have the supply pressure, regulator arrangement, gas piping, and manifold adjustment checked against the unit rating plate.
Pressure reading is unstable: Allow the unit to run for five minutes at steady state, confirm the correct pressure tap and tubing size, and check that the measuring device is connected correctly.
Gas odor is detected: Stop immediately, avoid flames and electrical switching, leave the area if necessary, and follow emergency gas-supplier instructions.
Leak is found after pressure testing: Shut off the gas, correct the connection, and repeat the leak check before operating the unit.
Harness or valve configuration is uncertain: Stop installation and verify the unit model, tenth model-number character, gas-valve type, and applicable conversion component.

Pros & Cons

Pros

Provides the main components required for natural-gas-to-LP conversion of supported LG/LD packaged rooftop units.
Supports both two-stage and modulating gas-valve configurations.
Includes replacement burner orifices, valve-conversion hardware, harness, pressure tubing, and identification labels.
Provides procedures for gas-flow verification, pressure measurement, manifold adjustment, and high-altitude operation.

Cons

Installation is not suitable for unqualified personnel.
Correct parts depend on the exact unit model and gas-valve configuration.
Additional pressure-measuring equipment and field-supplied gas-service components are required for commissioning.
Altitude adjustments and local code requirements can change the final setup procedure.

PDF

Faqs

Who should install the 508873-01 Natural to LP Gas Changeover Kit?

The 508873-01 kit must be installed by a qualified service agency or licensed professional familiar with gas-fired rooftop equipment and applicable codes. The installer must identify the unit and gas valve, shut off gas and electrical power, replace the correct burner orifices, complete the required valve conversion, install the harness, and verify combustion operation. Improper conversion can cause fire, explosion, carbon monoxide production, equipment damage, injury, or death.

Which packaged rooftop units and gas valves use the 508873-01 LP conversion kit?

This natural gas to LP propane changeover kit applies to LG/LD 024-074 packaged rooftop units when the unit nameplate and application table identify the correct configuration. Check the unit’s tenth model character to determine the gas valve and heating type. The kit application differs between two-stage and modulating equipment, so the installer should match the unit designation before beginning and must not substitute parts based only on physical appearance.

What must be done before installing the 508873-01 gas conversion kit?

Set the thermostat to Off or its lowest setting, shut off the unit’s gas supply, and turn off all electrical power at the disconnects. Some units may have multiple power supplies. Open the compressor and blower/heat access panels, then remove the mullion between them as instructed. Wear suitable protection around sheet-metal edges, and confirm the unit cannot start before removing the manifold or working near the burners.

How are the burner orifices replaced during natural gas to LP conversion?

After removing the manifold, replace only the orifices serving burners actually installed in the unit. The equipment may contain three, five, or seven burners, so unused positions should not receive an orifice. Install the LP orifices supplied with the kit, tighten threaded orifices to 6.25 foot-pounds, and do not apply thread compound. Reinstall and secure the manifold before continuing with valve and ignition-system modifications.

How does the gas valve conversion differ between two-stage and modulating units?

Two-stage units using a White-Rodgers 36J54 combination valve require the spring kit identified for that valve, including the manufacturer’s specified spring and LP labels. Modulating units using a 36J27 valve require the dedicated jumper kit and jumper plug. The installer must follow the instructions supplied with the applicable spring or jumper kit rather than mixing components between valve types.

Where is the J/P21 harness installed on the rooftop unit?

Locate the combustion air blower in the heating section and identify its four-position motor plug and matching unit jack. Disconnect the existing connection, verifying the unit-side wiring is marked P442-P19, then install the J/P21 kit harness between the combustion-air-blower motor plug and the unit jack. A qualified technician should confirm each connector is fully seated and routed safely before restoring power.

How is the converted LP heating operation checked after installation?

The technician should restore gas and electrical service, follow the automatic ignition start-up procedure, and allow the unit to operate until conditions stabilize. Gas flow, supply pressure, manifold pressure, ignition, and burner operation must be checked against the unit rating plate and applicable LP requirements. Pressure measurements require the correct valve-specific test connection. Afterward, remove test equipment, reseal pressure ports, and perform a gas-leak check.

What should be done if the converted unit does not ignite or locks out?

Do not attempt to light the burners manually; the unit uses direct spark ignition and has no pilot. During initial startup, air in the gas line may require the approved start-up sequence to be repeated. The control may attempt ignition several times before locking out. If lockout occurs, follow the gas shutoff and reset procedure exactly. If the appliance still will not operate, leave the gas off and have a qualified technician investigate.