Navien NFC-175 Installation & Operation Manual page 24

Navien is not responsible for performance issues of the domestic
system by scaling or accumulation of dirt; suitable steps shall
be taken by the installer and user to avoid water quality related
issues. Freeze Protection Navien recommends heat tracing and
insulating the DHW water pipes. Pipe enclosures may be packed
with insulation for added freeze protection. Freeze damage is not
covered by the warranty.
3.2.2 Essential Elements in a DHW System
DHW Heat Exchanger
The DHW heat exchanger installed inside the Navien NFC boiler
has been tested and certified in accordance with the latest IAPMO
standard PS 92.
Drain and Isolation Valves
Install drain and isolation valves on the inlet and outlet of the
DHW heat exchanger, so it can be flushed free of possible build-up
caused by dirt or hard water.
Pressure Relief Valve for DHW
To complete the installation of the DHW system, you must install
an approved / in, maximum 150 psi pressure relief valve on
3
4
the hot water outlet. The Navien NFC boiler has a built-in high
temperature shut off switch, so install a "pressure only" relief valve.
WARNING
Installing the pressure relief valve improperly may result
in property damage, personal injury, or death. Follow all
instructions and guidelines when installing the pressure
relief valve. The valve should be installed only by a licensed
professional.
24 About the Boiler
The DHW pressure relief valve is not supplied, but is required.
The following examples are pressure relief valves approved for use
with the boiler:
Wilkins P-1000A (Zurn Industries)
●
Conbraco 17-402-04
●
Watts Industries 3L (M7)
●
Cash Acme FWL-2, / in
3
●
4
Pressure
Relief Valve
CAUTION
Install the pressure relief valve as close to the boiler as possible.
No other valve should be installed between the pressure relief
valve and boiler.
When installing pressure relief valve, follow these guidelines:
Ensure that the valve's discharge capacity is equal to or greater
●
than the maximum pressure rating of the boilers DHW system.
Ensure that the maximum BTU/H rating on the pressure relief
●
valve is equal to or greater than the maximum input BTU/H
rating of the boiler.
Direct the discharge piping of the pressure relief valve so
●
that hot water does not splash on operator, or any nearby
equipment.
Attach the discharge line to the pressure relief valve and run the
●
end of the line to within 6-12 in (150 300 mm) of the floor.
Ensure that the discharge line allows for free and complete
●
drainage without restriction. Do not install a reducing coupling
or other restrictions on the discharge line.
If the relief valve discharges periodically, this may be due to
●
thermal expansion in a closed water supply system. Contact the
water supplier or local plumbing inspector on how to correct the
situation. Do not plug the relief valve.