Installing the System Piping 19
Back-flow 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.
●
Connect an air separator to the expansion tank only if the air
separator is located on the suction side of the system circulator.
●
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.
●
If an additional water fill connection is required for a specific
use, install the water fill 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, maximum 30 psi pressure 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 the example below,
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.
Refer to the following illustration for a pressure relief valve
installation in the space heating system. Conbraco Watts M330-M1
pressure relief valve (
3
/
4
in, HV, Max 30 psi) is provided with the
boiler.
Pressure Relief
Valve
Space Heating
Supply
Space Heating
Return
