
23
Installing the System Piping
A LWCO may be connected to the included PRV-Air
vent Adapter. The following illustration shows an
example of a separately installed external LWCO
using the PRV-air vent adapter.
6" (152 mm) min.
External LWCO
Method 2. Installation using the
PRV-air vent adapter
The external LWCO must be installed at least 6 in
(152 mm) above the top of the heat exchanger.
Refer to “3.7.2 Wiring Diagram - External LWCO” on
page 45 for typical wiring connections of the
LWCO to the boiler PCB.
Backflow Preventer
Install a backflow preventer valve in the make-up
water supply to the unit as required by local codes.
Low Water Cut Off (LWCO) Appliance
Internal LWCO
The Navien NFC-H boiler is equipped with a factory-
installed, pressure-sensing type low water cutoff
(LWCO) appliance. The minimum operation pressure
for this appliance is 6 psi by default.
Note
When the built-in water pressure sensor
detects insufficient water level in the
boiler, error code E302 is displayed on
the front panel requiring a manual boiler
reset.
Refer to local codes to determine if a LWCO
appliance is required for your system and ensure
that the built-in appliance meets the requirements.
External LWCO
If local codes require a separate LWCO appliance,
install one separately. The following figure shows an
example of a separately installed external LWCO.
6" (152 mm) min.
Method 1. Installation using a separately
installed external LWCO
External
LWCO
Содержание NFC-250/175H
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