Navien NPE-180S Conversion Manualline

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Condensing Water Heater

Gas Conversion 

Guide

Model

NPE-180A/210A/240A 

NPE-150S/180S/210S/240S

This water heater is configured for Natural Gas from the 

factory.  If conversion to Propane Gas is required, the 

conversion kit supplied with the water heater must be used.

WARNING

This conversion kit shall be installed by a qualified service 

agency* in accordance with Navien’s instructions and 

all applicable codes and requirements of the authority 

having jurisdiction. The information in these instructions 

must be followed to minimize the risk of fire or explosion 

or to prevent property damage, personal injury or death. 

The qualified service agency is responsible for the proper 

installation of this kit. The installation is not proper and 

complete until the operation of the converted appliance 

is checked as specified in the manufacturer’s instructions 

supplied with the kit. 

Procedure:

1.  Turn off both gas and water supply to the water heater.

2.  Using a Phillips hand screwdriver, remove 4 screws (2 from 

the top and 2 from the bottom) of the front cover assembly

to gain access to the internal components. See Figure 1 for 

illustration of the front cover on the unit.

Gas Valve

Gas Inlet 

Pipe

Figure 1.  

NPE Series Front cover 

Figure 2. NPE Series  

Internal Components

3.  Once the front cover is removed, place it in a safe 

location to prevent accidental damage. With the internal 

components exposed, locate the gas inlet pipe and the Gas

Valve near the left side of the unit which are highlighted in 

Figure 2.

6.  Once the Gas Orifice is exposed, remove the two screws 

that hold the part in place. Remove the Gas Orifice from 

its housing and prepare the new Gas Orifice for the LP 

conversion for installation.

Remove two (2) 

screws here

Figure 4. Access to Gas Orifice in Fan Assembly

WARNING

●

DO NOT adjust or attempt to measure gas valve outlet 

pressure. The gas valve is factory-set for the correct 

outlet pressure. This setting is suitable for natural gas and 

propane, requiring no field adjustment.

●

Attempting to alter or measure the gas valve outlet 

pressure could result in damage to the valve, causing 

potential severe personal injury, death or substantial 

property damage. Navien water heaters are shipped 

ready to fire natural gas ONLY. 

LP

NPE-150S 

NPE-180A/ 210A/ 240A/ 180S/ 210S/ 240S 

NG

Figure 6. Orifice identification

7.  Remove the Gas Orifice, ensure that the packing is properly

seated inside the port, and then install the new Gas Orifice 

for use with LP gas. Ensure that the Orifice is properly 

seated on the packing inside the port before proceeding 

to the next step.

Packings

Packing

8. Replace the gas inlet pipe to its original position and use 

all screws to secure all connections.

Note

Do not overtighten as this may damage or 

crack the components.

*  A qualified service agency is any individual, firm, corporation or 

company which either in person or through a representative is 

engaged in and is responsible for the connection, utilization, repair 

or servicing of gas utilization equipment or accessories; who is 

experienced in such work, familiar with all precautions required, and 

has complied with all of the requirements of the authority having 

jurisdiction.

In Canada: The conversion shall be carried out in accordance 

with the requirements of the provincial authorities having 

jurisdiction and in accordance with the requirements of the 

CAN‐B149.1 and CAN1‐B149.2 Installation Code.

Tools Required:

●

Phillips Screwdriver

●

Flathead Screwdriver

●

5

/

32

 in or 4 mm Allen Wrench

●

Combustion Analyzer or Dual Port Manometer 

●

Gas Leak Detector

Included Items:

●

Gas Orifice (refer to below table)

Model

NG

LP

NPE-150S

Ø 6.30

Ø 5.10

Model

NG

LP

1STAGE 2STAGE 1STAGE 2STAGE

NPE-180A/NPE-180S Ø 4.80 

Ø 5.95 

Ø 3.80 

Ø 4.70

NPE-210A/NPE-210S Ø 6.10

Ø 6.30

Ø 4.50

Ø 4.80

NPE-240A/NPE-240S Ø 6.10

Ø 6.30

Ø 4.50

Ø 4.80

Table 1. Orifice Size

●

Gas Pressure and Conversion Kit Number Labels

4. Use a Phillips screwdriver to remove the two screws at 

Location A - the connection below the Gas Valve where it 

connects to the pipe. See Figure 3 for reference. Once the 

screws are removed, carefully separate the pipe from the 

Gas Valve.

5. Once the gas inlet pipe is detached from the Gas Valve, find 

Location B - the connection above the Gas Valve where it is 

attached to the Fan Motor Assembly. Carefully remove the 

four screws by hand using a Phillips screwdriver and pull 

the Gas Valve away from the Fan Assembly to access the 

Gas Orifice.

Location B: 

Remove four (4) 

screws here

Location A: 

Remove two (2) 

screws here

Figure 3. Detaching Gas Valve from  

Gas Inlet Pipe and Fan Motor Assembly

O-ring

Gas Orifice

Packing

O-ring

Gas Orifice

Packing

180S/ 210S/ 240S>

Figure 5. Exploded view of Gas assembly

DANGER

See Figure 5. Inspect the O-ring between the gas valve and 

gas valve inlet adapter whenever they are disassembled. 

The O-ring must be in good condition and must be 

installed. Failure to comply will cause a gas leak, resulting in 

severe personal injury or death.

DANGER

Inspect the O-ring between the gas valve and gas valve 

inlet adapter whenever they are disassembled. The O-ring 

must be in good condition and must be installed. Failure to 

comply will cause a gas leak, resulting in severe personal 

injury or death.

9. Set the Front Panel Dip switch according to the gas type.

WARNING

Be sure to turn off the power before changing the DIP 

switch setting.

1      2    

NG

1      2    

LP

1       2      3      

1      2       

4      5      6      7      8      9     10

ON

ON

10.  Turn on the gas and water supply to the water heater.

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