Navien NPE-180A2 Installation Manual page 27

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
●
to the water heater are suitable for potable water
applications.
Do not introduce toxic chemicals, such as water
●
heater 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—
a mixing valve is required 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.
Do not configure the system for DHW
Note
recirculation when it is configured to
run an air handler using the H2Air add-
on controller. DHW recirculation and
Navien H2Air configurations cannot be
used at the same time.
3.4.2 Selecting a Recirculation Mode
("A2" Model Only)
On all "A2" 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 adjust the
recirculation settings on the front panel and set the
position of the 2-way valve inside the water heater.
Refer to "Included Items" on page 79.
When the optional ComfortFlow recirculation mode
is activated, energy consumption increases because
the water heater operates to maintain the water
temperature within the circulation loop. You can
use the Navien Intelligent Preheating feature, set
the weekly timer, or activate the HotButton feature
(additional accessories required) to reduce energy
consumption.
The recirculation feature of the "A2" models has
three performance advantages:
Lower Minimum Flow Rate is needed to produce
●
hot water.
Resolves hot/cold/hot stacking issue-the "cold
●
water sandwich" effect.
Quicker hot water delivery to fixtures, which
●
results in less water wasted.
When using external recirculation
Note
mode with the built-in pump, observe
the following maximum recirculation
pipe lengths including fittings (
pipe is recommended):
- / in. Copper Pipe-100 ft (30 m) of
1
2
equivalent length
- / in. Copper Pipe-500 ft (150 m) of
3
4
equivalent length
Lengths in excess of these limits will
require an external recirculation pump.
If PEX is used for the water piping,
consult with the pipe and fittings
manufacturer for sizing and equivalent
pressure drop information.
/ in.
3
4
Installing the Water Heater 27