Navien NHB Series Installation & Operation Manual page 48

Tighten the boiler connection valves with care to
Note
avoid damage.
The gas connection fitting on all boilers is
3/4 in rigid pipe can be used; refer to the sizing tables
on the proceeding pages for limitations. Avoid using
3/4 in corrugated connectors or tubing as noise may
occur.
When using flexible gas lines, ensure that the pipe's
inner diameter and connector is sufficient to supply
the required BTUs. Also, ensure that the flexible line
has no crimps or tight bends in it, as this will restrict
gas flow.
When using rigid pipe, Navien recommends the
installation of a union on the gas supply line close
to the boiler, to facilitate any future maintenance or
service.
CAUTION
Prior to using an excess flow valve (EFV) in the gas line, check
the manufacturer's minimum and maximum flow capacity
rating. An improperly sized EFV will not allow for a full flow of
gas to the boiler and may cause improper operation.
CLOSE: 460
MAX OPER: 375
BYPASS: 10
48 Connecting the Gas Supply
Corrugated Connector
CLOSE: 460
MAX OPER: 375
BYPASS: 10
Excess Flow Valve
Typical LP Gas piping examples:
3
/ in.
2 Stage System with Multiple Regulators (Recommended)
4
Gas Tank
Single Regulator System
Gas Tank
Gas Regulator (2 Stage)
Low Pressure Regulator
(to home or building)
High Pressure
Regulator
Gas Regulator
(12" WC)
Full Size
Pipe
Gas Pipe
Full Size
Gas Pipe
Full Size
Gas Pipe