Installation / Operation Instruction Manual

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Installation instructions
RTG-L-199/160N/X1 – 6 721 827 274 (2022/06)
4.12 Cascading Operation
Cascading allows up to twenty four appliances to be connected
in parallel. One of the appliances will serve as the controlling
primary appliance and will attempt to meet the hot water
demand. If the hot water demand is beyond the capacity of the
primary appliance, a signal is sent to one or more of the
secondary appliances to ignite. A cascading kit must be
installed for each secondary appliance included in the
installation.
Example: A 7 unit cascade installation includes 1 primary
appliance and 6 secondary appliances. 6 intelligent cascading
kits must be installed for this application.
4.12.1 Plumbing set up
The plumbing should be connected in the reverse return
method with a minimum number of elbows to aid in balancing
pressures between the appliances. Locating the appliances as
close as possible improves performance.
• Follow industry plumbing practices when installing multiple
appliances.
• Minimum pipe diameter: ¾"
• Minimum water pressure: 50 psi
• Maximum distance between appliances: 36"
• Insulate pipes to prevent heat loss
Fig. 33 Cascading installation example
It is not possible to have both cascading and recirculation active
at the same time.
It is not possible to cascade a RTGK with a RTGL.
4.13 Space heating applications
CAUTION:
▶ If the set point temperature is above 120°F (49 °C),
precautions should be taken to protect users of potable
water from scalding.
NOTICE:
▶ The use of a flow switch is recommended to ensure DHW
priority and to prevent “cold-blow” situations when the
Bradford White tankless water heater is used with an air
handler.
Air handler installation must include a pump.
The flow switch should be used to disable the blower on the
air-handling system when domestic water is used.
NOTICE:
▶ Ensure the primary pump is properly sized to provide
adequate flow for the system heat load.
For external pump sizing please refer to the pressure drop
curves, fig. 35. Also remember to account for system piping
pressure loss. A minimum of 1.7 GPM is recommended to
provide adequate flow through the water heater when
determining the size of the primary pump.
If the application requires larger flow rates, such as for use with
an air handler, tank loading, or a large home, we recommend the
use of the RTGK model paired with one of the recommended
external pumps from the application manual, available online.
Bradford White tankless water heaters are approved for
use in combination DHW and space heating applications
(open-loop setup).
These water heaters are not approved for use in space heating
only applications (closed-loop setup). Figure 34 gives an
example of a combination DHW and space heating application
that is allowable. Use of tankless water heater in a combination
DHW and space heating application will result in the product
warranty being reduced to 3 years.