RBI SERIES 8800 Installation & Operation Manual page 16

Page 16
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 35°F, 19.4 ° C .
Cold Water Supply
The cold water supply must be piped to 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 below. A typical water
heating system is shown in Figure 10 and 11.
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
Table 7A - 8800 and 8900 Heat Exchanger Selection Graph
SERIES 8800 & 8900 INSTALLATION AND OPERATING INSTRUCTIONS
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 thermo-statically 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 growth of water born bacteria.