Installing A Cascade System; Connecting Water Supplies - Navien NHB Series Installation & Operation Manual

8. Installing a Cascade System

When installing a cascade system, carefully consider the design of the system and the features of the installation location. Follow all local
codes and regulations, as well as all guidelines for installing the boiler. The following sections describe additional considerations that are
specific to installing cascade systems. Read them carefully before designing or installing the system.

8.1 Connecting Water Supplies

Several options are available for configuring a cascade system of boilers. The options shown here are only examples. The setup you choose
will vary based on the installation location, local building codes, and other factors. Follow all applicable regulations when installing a cascade
system.
You can connect up to 32 boilers to meet high-volume heating demands. Some possible connection options include the following:
Example of a Basic Cascade System Application
Supply
Cold water
Back flow preventor
Expansion tank
Return
System application drawings are intended to explain the system piping concept only.
Note
Install a filter in the system return to remove foreign objects from the system. Foreign objects inside the system may result in
abnormal system operation.
Refer to "3.3 Filling the System" on page 29 for make-up water connections and refer to the requirements of your local codes
to ensure compliance.
Use pumps with integral check valves or install check valves at the pump outlets.
Navien universal temperature sensors (#GXXX001769) must be installed for cascade system operation.
Adjust the settings at the main unit as the cascade system uses only the main unit settings. Changes made to the sub units are
ignored.
Refer to "11.6.4 Configuring a Cascade System" on page 103 to make adjustments to the boiler staging settings. By default,
boilers will be added to the system when the input capacity exceeds 60%, and removed when the input capacity falls below
30%.
Depending on the installation environment, the supply top and return top piping option can be applied.
Air separator
Temperature
12" (30 cm)
sensors (required)
maximum
[NFB-301C/399C]
Main Sub1 Sub2
Installing a Cascade System 65