Navien NFC-250/175H Installation Manual page 24

Expansion Tank
An expansion tank must be installed in the space
heating piping to prevent excessive pressure
from building in the system. See the examples of
system application at the end of this section for the
installation location. Refer to the expansion tank
manufacturer's instructions for additional details.
Follow the guidelines below when installing an
expansion tank.
Connect an air separator to the expansion tank
●
only if the air separator is located on the suction
side of the system pump.
Install the make-up water connection at the same
●
location as the expansion tank's connection to
the system.
When replacing an expansion tank, consult the
●
expansion tank manufacturer's literature for
proper sizing.
For diaphragm expansion tanks, always install
●
an automatic air vent on the top side of the air
separator to remove residual air from the system.
Isolation Valves and Unions
Full port ball valves are required for the boiler
●
system. Failure to use full port ball valves could
result in a restricted flow rate through the boiler.
Check valves are recommended for installation.
●
Failure to install check valves could result in a
reverse flow condition during pump(s) off cycle.
Unions are recommended for unit serviceability.
●
Magnetic Filtration
This must be connected to the space heating return
in the near boiler piping to protect the boiler from
iron oxide (magnetite) that may be produced from
cast iron or steel type system piping and heating
accessories. Refer to the included instructions for
installation details.
NaviClean (Magnetic Filter) is available for purchase
separately.
24 Installing the System Piping
Pressure Relief Valve
To complete the space heating system installation,
you must install a / in, 30 to 80 psi (max) pressure
3
4
relief valve on the space heating hot water outlet.
An ASME approved HV pressure relief valve for space
heating system is supplied with the boiler.
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.
The pressure relief valve must be installed at
●
the boiler outlet and in the vertical position,
as shown in this section, with the drain pipe
outlet exiting the side of the pressure relief
valve horizontally and elbowing down.
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 the 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 boiler's space heating 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 the
operator or equipment.
Attach the discharge line to the pressure relief
●
valve and install the end of the line within 6-12 in
(150-300 mm) of the floor drain, making the
discharge clearly visible.
Do not direct the discharge line to a location
●
where freezing could occur.
Ensure that the discharge line is not plugged or
●
obstructed.