SPECTRUM INSTALLATION AND OPERATING INSTRUCTIONS
Page 14
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 selections. If local water conditions
are extreme follow the guidelines in the Heat Exchanger
Selection Table (Table 7A) and the Pumping
Performance Table (Table 7B). 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 flow prevention devices are installed.
Pump Requirements
This low-mass water heater requires a continuous mini-
mum water flow for proper operation. The factory
recommended circulating pump has been sized to
overcome the head loss of the water heater plus a 30
foot piping loop under normal water conditions. Table 7B
provides the heat exchanger pressure drop chart and
temperature rise table.
The temperature rise across the
water heater must never exceed 30
°
F, 16.7
°
C.
CAUTION: The maximum allowable flow rate through
a Spectrum water heater is 92 GPM,
5.8 L/s
(2-pass
heat exchanger) and 46 GPM,
2.9 L/s
(4-pass heat
exchanger). The cupro-nickel heat exchanger allows
for 100 GPM,
6.3 L/s
(2-pass heat exchanger) and 50
GPM,
3.2 L/s
(4-pass heat exchanger). See Table 7B.
Cold Water Supply
The cold water supply must be piped to the storage tank
on the water heater’s outlet piping between the water
heater and the hot water storage tank. This will prevent
untempered water from entering the water heater, see
the Temperature Rise Control section. A typical water
heating system is shown in Figures 8 and 9.
Temperature Rise Control
Water returned to the water heater inlet must not be less
than
110
°
F
,
43
°
C or excessive condensation of the
products of combustion will damage the water heater
voiding the warranty. The 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 flow
rate through the heat exchanger. Thermometers are
installed on both the inlet and outlet of the water heater
for determining the temperature rise through the unit.
The proper velocity through the water heater must be
maintained in accordance with Table 7B for efficient
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 7B the flow rate is
too low. Scaling and softening 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.
The mixing valve MUST be set to prevent a scald injury
from occurring, see the caution against scalding.
Storage of water for domestic use above
140
°
F
,
60
°
C
will provide an increased quantity of tempered water and
help prevent the growth of water born bacteria.
