Navien NFC-175 Installation & Operation Manual page 22

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.
When installing the pressure relief valve, follow these guidelines:
Ensure that the valve's discharge capacity is equal to or greater
●
than the maximum pressure rating of the boiler's space heating
system.
Ensure that the maximum BTU/H rating on the pressure relief
●
valve is equal to or greater than the maximum input BTU/H
rating of the boiler.
Direct the discharge piping of the pressure relief valve so that
●
hot water does not splash on the operator or equipment.
Attach the discharge line to the pressure relief valve and install
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the end of the line within 6-12 in (150-300 mm) above the floor.
Ensure that the discharge line provides complete and
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unobstructed drainage. Do not install a reducing coupling or
other restrictions on the discharge line.
If the relief valve discharges periodically, this may be caused by
thermal expansion when the expansion tank is full or undersized.
Do not plug the relief valve.
The illustration below shows an example of a pressure relief valve
and an air vent installed with the PRV-air vent adapter included in
the accessory box.
22 Installing the System Piping
Pressure
Relief Valve
Method 1.
Depending on the installation conditions, pressure
Note
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relief valves (not included and for separate purchase)
of up to 80 psi can be used.
Refer to "11.4.3 Setting the Operation Parameters
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- 16. High Sys Pressure" on page 96 to adjust the
upper limit pressure lockout setting when using a
higher rated valve.
Ensure that the manifold system included in the
●
accessory box must be installed.
CAUTION
All field supplied pressure relief valves must be ASME certified.
Air Vent
External LWCO