Navien NFB-175H, Руководство по установке, Страница: 20 / 135

20 Installing the System Piping
●
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.
Pressure Relief Valve
To complete the space heating system installation,
you must install a
3
/
4
in, 30 to 80 psi (max.) pressure
relief valve on the space heating hot water outlet.
An ASME approved Watts 174A pressure relief valve
( 3 /
4
in, HV, Max 30 psi) is provided 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.
External LWCO
If local codes require a separate LWCO device,
install one separately. Combining the LWCO with
the air vent simplifies the installation. The following
illustration shows an example of a separately
installed external LWCO.
6" (152 mm) min.
External
LWCO
The external LWCO must be installed at least 6 in
(152 mm) above the top of the heat exchanger.
Refer to “3.6.2 Wiring Diagram - External LWCO” on
page 36 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.
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.