2
Gas Piping Connections
Water Piping Connections
Condensate Drain Connection
A condensate drain pipe must be connected to the 1/2” condensate outlet fitting at
the bottom of the unit and water must be poured into the exhaust connection to fill
the condensate trap.
The end of the 1/2
”
(NPT) plastic piping should drain into a laundry tub or into a floor
drain.
Do not submerge the end of the
pipe in water.
Note
Syphon
Condensate Outlet
Water
Floor drain
The boiler is recommended to be the first
appliance to be connected to the gas supply
line.
Gas meter
’
s capacity
≥
Total gas capacity of connected appliances
Gas supply
Gas
Regulator
Bottom View
Gas Inlet Adapter
Gas Supply Line
Example:
Gas meter
425 CFH
≥
Boiler
195 CFH
+
Furnace
58.8 CFH
+
Domestic gas stove
63.7CFH
* 1 CFH=1,020 Btuh
•
1/2" rigid pipe can be used; refer to the sizing tables in the Installation &
Operation Manual for limitations. Avoid using 1/2" corrugated connectors
or tubing as noise may occur.
Built-in Water Fill Connection
Navien NCB boiler is equipped with
an auto-feeding water connection
and motorized feeding valve.
Therefore, installation of additional
system water fill connection is not
necessary in most cases.
Note
Backflow
Preventer
Make-up
Water
External Water Fill Connection
Heating
Supply
Expansion Tank
Circulator
Pressure Relief Valve
Air Separator
Warning
Water Piping Connections
Space Heating System
DHW System
Install the included 3/4 in, maximum 30
psi pressure relief valve on the space
heating supply.
An ASME approved HV pressure relief
valve for space heating system is
supplied with the boiler.
The DHW pressure relief valve is
not supplied, but is required.
Install an approved 3/4 in,
maximum 150 psi pressure relief
valve on the hot water outlet.
Space
Heating
Return
Space
Heating
Supply
Pressure Relief
Valve
Pressure
Relief
Valve
Cold Water
Supply
DHW
Supply
Space
Heating
Supply
Space
Heating
Return
DHW
Supply
Cold
Water
Inlet
Built-in
Water Feeder
Connection
Flow Restrictor (for DHW system)
Flow Rate (GPM) and Water Pressure (psi)
Orange
Yellow
Blue
The boiler has a built-in flow restrictor at
the cold water inlet adapter to limit the
overall DHW flow. Three additional flow
restrictors are provided for different flow
rates.
Refer to the following graph and install
an appropriate restrictor for your DHW
system. See the Installation & Operation
Manual (page 21, 22) for detailed
procedures.
Flow Restrictors (Orange, Yellow, and Blue)
Ensure that the Air Vent Cap is removed
before filling the system.
System will not be properly filled
without the air vent cap removed. Air in
the system may cause malfunctions
and system overheating.
Make-up
Water
Direct to the
external drain
To the drain via
a neutralizer
External drain
To the laundry
tub
To the laundry tub
via a condensate pump
System Fill Connection
The Navien NCB boilers
have a built-in air vent
on top of the internal
circulator to purge air
from the boiler system.
Air Vent Cap
Before filling the boiler, remove the air vent cap to
allow the system to fill properly. Replace the cap
when the system is full.
Heating
Return
