Considerations For System Applications - Navien NFC-250/175H Installation Manual

2. Close the manual and automatic air vents and
the boiler drain valve.
3. Fill the boiler to the correct system pressure. The
correct pressure will vary with each application.
The typical cold water fill pressure for a
residential system is 12 psi. The pressure will rise
when the boiler is turned on and the system
water temperature increases. The operating
pressure must never exceed the relief valve
pressure setting.
4. At initial fill and during boiler start-up and
testing, check the system thoroughly for leaks.
Repair any leaks before proceeding further.
WARNING
Eliminate all system leaks. The continual
introduction of fresh makeup water will reduce
boiler life. Minerals can build up in the heat
exchanger, reducing heat transfer, overheating
the heat exchanger and causing heat exchanger
failure.
The system may have residual substances that
could affect water chemistry. After the system has
been filled and leak tested, verify that water pH and
chlorine concentrations are within the acceptable
range by performing sample testing.
CAUTION
Before operating the boiler for the first time,
ensure that the boiler system is filled with water.
Purge the air inside the system to avoid damage
to the boiler.
34 Installing the System Piping
3.6 Considerations for System
Applications
Read and follow the guidelines listed below when
installing system piping for the Navien NFC-H boiler:
System application drawings are intended to
●
explain the system piping concept only.
For the upstream side of all pumps, use straight
●
pipes with a minimum inside diameter of
/ in (12 mm).
1
2
Provide a system expansion tank following the
●
guidelines on page 24.
System installations must comply with all local
●
codes.
Air Removal
The boiler and system piping layout must be
configured to promote the removal of air from the
system. Air vents and bleeders must be strategically
placed throughout the system to aid in purging
the air from the system during commissioning of
the boiler. The system must also employ the use of
an air removal appliance, such as an air eliminator
designed to remove the air from the water as it
flows through the system.
Follow the installation instructions included with
the air removal appliance when placing it in the
system; air removal appliances generally work better
when placed higher in the system. Always locate
air removal appliances in areas of the system that
have a guaranteed positive pressure, e.g., in close
proximity to the water fill and expansion tank.
Connecting an air vent on top of the
Note
boiler is recommended.