Selecting A Recirculation Mode - Navien NPE-180A Service Manual

4.5 Selecting a Recirculation Mode

On all "A" model Navien water heaters, you can choose from
two pre-heating modes: internal recirculation mode or external
recirculation mode. To select a recirculation mode, you must set
the DIP switches on the front panel, and set the position of the
2-way valve inside the water heater. By default, the DIP switches
are set to OFF.
When you use a recirculation mode, there will be some minor
efficiency loss as a result of the water heater maintaining a steady
temperature within the circulation loop. Although in many cases,
higher gas usage will be made up for by lower water usage.
The recirculation feature of the "A" models has three performance
advantages:
Elimination of any minimum flow rate requirement.
●
Elimination of any hot/cold/hot stacking—the "cold water
●
sandwich" effect.
Quicker hot water delivery to fixtures, which results in less water
●
wasted.
NOTE
When using external recirculation mode with the built-in
pump, observe the following maximum recirculation pipe
lengths including fittings (3/4" pipe is recommended):
-1/2" Copper Pipe- 100' (30m) of equivalent length
-3/4" Copper Pipe- 500' (150m) of equivalent length
Lengths in excess of these limits will require a properly sized
external recirculation pump.
Internal Recirculation Mode
To use the internal recirculation mode:
1. Connect the water supply. Refer to the "Installation Manual
(page 19)".
2. Set the 2-way valve inside the water heater to "INT. "
3. Set the front panel DIP switches at the far left (set of ten) to:
1—ON; 2—OFF.
ON
1 2 3 4 5 6
The following diagram shows the internal recirculation flow for
pre-heating:
Primary Heat Exchanger
Buffer
Secondary Heat Exchanger
Tank
Circulation
2-Way
Pump
Valve
Open
Hot Water
Supply
Internal Recirculation Mode
ON
7 8 9 10
Flow
Sensor
Check
Valve
Water
Adjustment
Valve
Domestic Water
Supply
System Details 27