Installing the Water Heater 21
3.4.1 Using the Water Heater for Combination
Water Heating and Space Heating
When using the water heater for both water (potable) heating and
space heating, follow these guidelines:
Ensure that all piping and components connected the water
heater are suitable for potable water applications.
Do not introduce toxic chemicals, such as boiler treatments, into
the potable water.
On Combi applications, circulators suitable for DHW applications
must be used.
Do not connect the water heater to any heating systems or
components that have been previously used with non-potable
water heaters.
If the system requires varying temperatures for water—for
example, hotter water for space heating than for other uses—
install a mixing valve to temper the water and reduce the
potential for scalding.
Do not use the water heater for space heating only.
Make sure circulator flow rate through the Water Heater does
not exceed 4 GPM.
CAUTION
Do not configure the system for DHW recirculation when it is
configured to run an air handler using the ComfortAir+ add-
on controller. DHW recirculation and Navien ComfortAir+
configurations cannot be used at the same time.
3.4.2 Selecting a Recirculation Mode ("A" model
only)
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.
The following is a typical water piping example for NPE-180A/
210A/ 240A models.
Pressure
Relief Valve
Union
Full port
Gas Valve
Gas Supply
Expansion
Tank
Hot Water Supply
Recirculation Line
Shutoff Valve
Condensate Drain
Cold Water
Supply
[NPE-180A/ 210A/ 240A]
The following is a typical water piping example for NPE-180S/
210S/ 240S models.
Pressure
Relief Valve
Shutoff Valve
Hot Water
Supply
Union
Full port
Gas Valve
Gas Supply
Cold Water
Supply
Condensate Drain
[NPE-150S/ 180S/ 210S/ 240S]
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