A.O. Smith THR-160, Инструкция по установке и руководство по эксплуатации и уходу

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34 • Residen al Gas Tankless Water Heater Use and Care Guide
INSTALLATION
Recircula on
Internal Pump
This water heater comes with an
integrated recircula on pump, which
is deac vated by default from the
factory. The water heater has 3
recircula on mode op ons:
• Recircula on with a dedicated
return line
• Crossover recircula on mode
• On-Demand mode compliant with
California’s Title 24
Details of the opera on are listed
below. In each mode, the heater’s
pump only operates when there is not
any demand from the home’s
fi xtures.
The water heater will stop the pump
if there is a demand from one of the
home’s
fi xtures.
• Recircula on with a Dedicated
Return Line - In this mode, the
water heater will operate the pump
in order to keep your water lines
warm, reducing the me it takes
for the hot water to arrive at the
fi xture. The user can con fi gure Two
Pump Timer ON periods where the
heater will operate the pump. It
is recommended to set the Pump
Timers to ON during mes when
the home is occupied. The water
heater will operate as an on-
demand water heater during Pump
Timer O
ff periods, though there
may be a delay ge ng hot water to
the
fi xture. See “Se ng the Pump
Timers” on page 52 to set the
Pump Timers.
• Crossover Valve Mode - In this
mode, a “crossover” valve is typical-
ly installed at the home’s furthest
fi xture. This valve will use the
home’s cold water line to act as the
return line. The se ngs on the valve
are dependent on the manufacturer.
For example the typical opera on is
as follows; the crossover valves have
a type of thermal valve that will
open up when the water tempera-
ture on the hot side drops below
95°F (35°C) and will close when the
temperature reaches 105°F (40.5°C).
NOTICE: These temperature values
may vary from manufacturer to
manufacturer. Refer to Tables 20
and 21 to set the Crossover Valve
Recircula on mode and the Pump
Timers. For manufacturer recom-
mended crossover valve see “Avail-
able Accessories” on page 15.
NOTICE: Func on/compa bilty may
vary with other crossover valves.
• On-Demand Mode - In this mode
the pump will only operate when
ac vated by the user through one
of the wireless push bu ons. A
Remote Recircula on Kit is required
see “Available Accessories” on
page 15. This kit consists of
one receiver wired to the water
heater and at least one push
bu on. The receiver can pair with
up to 30 push bu ons. Instruc ons
are provided with the receiver
kit. This mode is compliant with
California’s Title 24 Code. In this
mode, the pump will run un l the
inlet water temperature reaches
the deac va on temperature set in
mode A04 for Recircula on with a
Dedicated Return Line or when the
crossover valve closes if in Crossover
Recircula on. The pump will stop if
it is s ll running a er 5 minutes.
Table 13: Maximum Pipe Length
Hot Water supply line and
Dedicated Return line
Pipe Diameter Pipe Length
3/4" 500 ft (152.4 m)
1/2" 200 ft (61 m)
NOTE: These are equivalent length
that includes head loss for elbows,
tees, unions, etc for smooth wall
copper tube. Other water tube
materials have di
ff erent head
loss characteris cs. When other
materials are used, the installer
shall consult with the water tube
manufacturer to conduct a head loss
calcula on to make sure the installed
pump will
fl ow at least 2 gpm.
Please refer to the manufacturer’s
speci
fi ca on sheet for pump head
loss informa on. An addi onal pump
may be necessary for circula on
systems with longer equivalent pipe
lengths.
External Pump
When installing an external
recircula on pump, care must be
taken to properly size the pump
for the applica on. Sizing must
be performed by the installing
contractor or engineer. The following
requirements need to be observed
when sizing:
• Size the recircula on pump to fl ow
no less than 2 gpm (7.6 l/m) and no
more than 4 gpm (15.1 l/m) per ac-
vated heater. The manufacturer’s
suggested fl ow rate is 3 gpm (11.4
l/m). Refer to the water heater’s
pressure drop chart on its speci
fi ca-
on sheet for losses at other fl ow
rates. Head loss at 3 gpm is approxi-
mately 16.9 . of head (7.3 psi)
• The pump should be controlled
by a fi eld supplied aquastat with
immersion probe and an adjustable
di
ff eren al. The minimum suggested
di ff eren al is 15 °F (8.3 °C). NOTE:
Running the pump con nuously will
reduce the warranty of the water
heater.
• An air elimina on device is suggest-
ed to remove air from the piping
system. Air may cause the recircu-
la on pump to cavitate and may
reduce the water
fl ow rate. These