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Cast Iron Condensing Boilers – Installation Manual
Torus Stainless Steel Condensing Boilers & Water Heaters – Installation Manual
DOMESTIC WATER SUPPLY PIPING
Proper controls 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
The 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 boiler as possible to prevent excessive
head loss which will reduce flow.
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.
Two typical water heating systems are shown in Figures
14 & 15.
Thermostatic Mixing Valve- Water Above 140°F, 60°C
Water can be stored a 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 above.
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.
Water Chemistry
The required temperature rise across the primary heat
exchanger is based on water having a hardness
between 4 and 12 grains per gallon with a level of
dissolved solids not exceeding 350 ppm. Water having
a hardness less than 4 grains can cause excessive
corrosion of the heat exchanger. Water that has a
hardness greater than 12 grains per gallon and/or a
level of dissolved solids exceeding 350 ppm will require
a larger circulating pump and temperature rise. Water
hardness greater than 15 grains per gallon will require a
water softner system.
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 pump selections. Scale free
operation can be achieved when properly following the
guidelines in (Table 8). 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.
Table 8
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
minimum water flow for proper operation. When making
pump selections, proper velocity through the water
heater must be maintained for efficient operation and
long life. If the temperature rise is too high, the flow rate
is too low. Scaling and softening of the primary heat
exchanger will occur.
The temperature rise across the
primary heat exchanger must never exceed the flow
rates listed in Table 8.
Water Heater Min Flow Rates
pH Level
6.5-8.5
Water
Hardness
Normal (4 to 12) gpg
Hard (12-15) gpg
Model
GPM
Delta-t
Drop (ft)
GPM
Delta-t
Drop (ft)
1250
99
24.5
10.5
132
18.4
18.3
1500
110
26.5
10.1
147
19.8
16.8
2000
138
28.1
11.2
183
21.2
18.3
2500
214
22.7
13.4
285
17
20.2
3000
214
27.5
13.4
285
20.6
20.2
4000
280
28
11.4
372
21.1
18.4
