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Finned copper tube gas boilers & water heaters – Boiler Manual
14
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Pump Requirements
Th is low-mass water heater requires a continuous mini-
mum water fl ow for proper operation. Th e 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 9B provides the heat exchanger pressure drop chart and
temperature rise table.
Th
e temperature rise across the water
heater must never exceed 30°F,
16.7°C
.
Th e maximum allowable fl ow 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). Th e
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 9B.
Cold Water Supply
Th e 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. Th is 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. Th
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 fl ow rate through the heat
exchanger. Th ermometers are installed on both the inlet and outlet
of the water heater for determining the temperature rise through
the unit.
Th e proper velocity through the water heater must be maintained
in accordance with Table 9B for effi 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 fl ow rate is too low.
Scaling and soft 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.
Th e 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.
