2
Gas Piping
C
onnections
Water Piping
C
onnections
C
ondensate Drain
C
onnection
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.
N
ote
Syphon
Condensate Outlet
Water
Floor drain
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.
B
uilt-in Water Fill
C
onnection
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.
N
ote
Backflow
Preventer
Make-up
Water
External Water Fill
C
onnection
Air Separator
Circulator
Expansion Tank
To System
Make-up
Water
From
System
Warning
Water Piping
C
onnections
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.
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
ent 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
System will not be properly filled
without the air vent cap removed. Air in
the system may cause malfunctions
and system overheating.
a. Direct to the
external drain
c. To the laundry tub
d. To the laundry
Tub via a condensate pump
b. To the drain via
A neutralizer
System Fill
C
onnection
The Navien NCB boilers
have a built-in air vent
on top of the internal
circulator to purge air
from the boiler system.
Th
ha
on
cir
fro
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.
