Instruction manual
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DOMESTIC WATER SUPPLY PIPING
Proper control se ings must be used to prevent water
supplied for domestic use from exceeding 130°F, 54°C
or a scald injury will occur! When higher water
temperatures are required for appliances such as a
dishwasher, a mixing valve or some other tempering
means must be installed. Households with small
children may require water temperatures less than
120°F, 49°C. Local codes must be complied with!
General Piping Requirements
Ensure that the water heater is equipped with bronze headers. Piping
and components connected to the water heater must be suitable for
use with potable water. e water heater must not be connected to
any heating system piping or components previously used with a
non-potable water heating appliance. No toxic chemicals, such as those
used for boiler treatment, are to be introduced into the potable water
used for space heating. If a hot water storage tank is used in the system
it must be equipped with a temperature and pressure relief valve
that complies with ANSI Z21.22 or CAN-4.4 and CAN-4.6.
e storage tank must be located as close to the water
heater as possible to prevent excessive head loss which
will reduce ow.
Water Chemistry
e required temperature rise across the water heater is based on
water having a hardness between 8 and 18 grains per gallon with
a level of dissolved solids not exceeding 350 ppm. Water having a
hardness less than 8 grains can cause excessive errosion of the heat
exchanger. Water that has a hardness greater than 18 grains per
gallon and/or a level of dissolved solids exceeding 350 ppm will
require a recalculation of the pump size and temperature rise.
A cupro-nickel heat exchanger may also be required. The
manufacturer should be consulted when these water conditions are
encountered. See Table 9A
e maximum allowable ow rate through a LCD water
heater with copper heat exchanger is 92 GPM, 5.8 L/s
on 225 1200 models and 115 GPM, 7.3 L/s on 1480 to
2300 models. e cupro-nickel heat exchanger allows for
100 GPM, 6.3 L/s on 225 to 1200 models 125 GPM,
7.9 L/s on 1480 to 2300 models, see Table 9B .
RBI water heaters are designed to run scale free. Due to the extreme
variables of water conditions world wide it is necessary to consider
pH values and water hardness in relationship to scaling. It is crucial
to consider these two variables when making heat exchanger and
pump selection. If local water conditions are extreme follow the
guidelines in the Heat Exchanger Selection Table (Table 9A) and the
Pumping Performance Table (Table 9B). Scale free operation can be
achieved by using water with a hardness between 8 and 18 and by
maintaining the pH between 5 and 9. Follow the conditions listed
under NORMAL in the table. In some areas of the country additional
precautions must be observed due to unusual characteristics of the
local water supply. Call the nearest RBI representative for details.
To properly size the pump a grain hardness and pH test must be taken
at the installation site before the order is placed. Proper pump sizing
will improve heater performance and help ensure heater longevity.
Expansion Tank
An expansion tank or other means to control thermal expansion
must be installed in the water heating system if back ow prevention
devices are installed.
Cold Water Supply
e cold water supply must be piped to the water heater’s outlet
piping between the water heater and the hot water storage tank.
is will prevent untempered water from entering the water heater,
see the Temperature Rise Control section below. A typical water
heating system is shown in Figure 14 and 15.
Pump Requirements
is low-mass water heater requires a continuous minimum water
ow for proper operation. e low water ow switch provided for
this unit will shut down the water heater if ow falls below the
required minimum level. Table 9B provides the heat exchanger
pressure drop chart and temperature rise table. e temperature
rise across the water heater must never exceed 35°F, 19.4°C.
Temperature Rise Control
Water returned to the water heater inlet must not be less than 125°F,
52°C or excessive condensation of the products of combustion will
damage the water heater voiding the warranty. e method outlined
below can be employed to prevent this condition from occurring.
A balancing valve should be installed on the outlet side of the water
heater for purposes of adjusting the ow rate through the heat
exchanger. ermometers are installed on both the inlet and outlet
of the water heater for determining the temperature rise through the
unit. e proper velocity through the water heater must be maintained
in accordance with Table 9B for e cient operation and long life.
If the temperature rise through the water heater is lower than
recommended the water velocity is too high. Premature erosion of
the heat exchanger will occur. Conversely, if the temperature rise is
higher than recommended in Table 9B the ow rate is too low. Scaling
and so ening of the heat exchanger will occur.
Thermostatic Mixing Valve -
Water Above 140°F, 60°C
Water can be stored at temperatures above 140°F, 60°C provided
that a thermostatically controlled mixing valve is used to temper
the hot water to an acceptable temperature before it’s supplied for
domestic use.
e mixing valve MUST be set to prevent a scald injury from
occurring, see the caution against scalding above.
Storage of water for domestic use above 140°F, 60°C will provide
an increased quantity of tempered water and help prevent growth
of water born bacteria.