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Finned copper tube gas boilers & water heaters – Boiler manual
FTXLF-IOM-HN-1-110308 Copyright 2008 Mestek, Inc.
Domestic WAter sUppLy pipinG
Proper controls must be used to prevent water supplied
for domestic use from exceeding 130
o
F, 54
o
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
o
F, 49
o
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. The 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.
The storage tank must be located as close to the water
heater as possible to prevent excessive head loss which
will reduce flow.
Water chemistry
The 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 corrosion 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 cupronickel heat exchanger may also be required. The
manufacturer should be consulted when these water conditions are
encountered. See Table 8, page 20.
The maximum allowable flow rate through a Futera XLF
water heater is 260 GPM, 16.4 L when equipped with
copper tubes. The cupronickel heat exchanger allows for
315 GPM, 19.9 L/s. See Table 9, page 20.
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
temperAtUre rise controL
Water returned to the water heater inlet must
not be less than 140
o
F, 60
o
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 9,
page 20 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 9, page 20 the
flow rate is too low. Scaling and softening of the
heat exchanger will occur.
Thermostatic Mixing Valve – Water Above 140
o
F,
60
o
C Water can be stored at temperatures above
140
o
F, 60
o
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
o
F,
60
o
C will provide an increased quantity of
tempered water and help prevent the growth of
water born bacteria.
