Installing A Cascade System; Connecting Water Supplies - Navien NHB H Series Installation And 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 plumbing 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 16 boilers to meet high-volume heating demands. Some possible connection options
include the following:
Example of a Basic Cascade System Application
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Sub2 Sub1
System application drawings are intended to explain the system piping concept only.
Note
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Install a filter in the system return to remove foreign objects from the system. Foreign objects inside
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the system may result in abnormal system operation.
Refer to "3.3 Filling the System" on page 26 for make-up water connections and refer to the
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requirements of your local codes to ensure compliance.
Use pumps with integral check valves or install check valves at the pump outlets.
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Navien system supply (Included box)/return (Accessory) Temperature sensor must be installed for
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cascade system operation.
Adjust the settings at the main unit as the cascade system uses only the main unit settings.
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Changes made to the sub units are ignored.
Refer to "11.13.4 Configuring a Cascade System" on page 114 to make adjustments to the boiler
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staging settings. By default, boilers will be added to the system when the input capacity exceeds
70%, and removed when the input capacity falls below 30%.
Connect zone pumps to the zone controller. Do not connect zone pumps to the main or sub units.
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72 Installing a Cascade System
Air separator
Main
Temperature
sensors (required)
[NHB-110H/150H]
Backflow preventer
Expansion tank
12" (30 cm)
maximum
Supply
Cold water
Return