Heating System Piping - RBI DOMINATOR Series Installation And Operation Manual

HEATING SYSTEM PIPING

General Piping Requirements
All heating system piping must be installed by a qualifi ed
technician in accordance with the latest revision of the
ANSI/ASME Boiler and Pressure Vessel Code, Section
IV, and, when required, ANSI/ASME CSD-1, Standard
for Controls and Safety Devices for Automatically Fired
Boilers. All applicable local codes and ordinances must
also be followed. A minimum clearance of 1 in, 25 mm
must be maintained between heating system pipes and
all combustible construction. All heating system piping
must be supported by suitable hangers not the boiler.
The thermal expansion of the system must be considered
when suppor ting the system. A minimum system
pressure of 12 psig, 82.7 kPa must be maintained.
Heating Boiler Piping Connections
The supply and return piping should be sized to suit the
system. The supply and return connection sizes are
listed in Table 8.
Table 8 - Supply & Return Connection Sizes
Model Size
300 thru 2100 2 1/2" NPT
Pump Requirements
This low mass boiler requires a continuous minimum
water fl ow for proper operation. The system pump must
be sized to overcome the head loss of the boiler and the
heating system in order to achieve the required
temperature rise. Table 7 provides the heat exchanger
pressure drop and temperature rise figures. The
temperature rise across the boiler must never exceed
35° F, 19.4° C.
CAUTION: A temperature rise outside of the range
listed in Table 7 indicates that the fl ow rate through the
heat exchanger is incorrect which will damage the
heat exchanger voiding the warranty! The maximum
allowable temperature rise is 35°F, 19.4°C.
The maximum allowable flow rate through a
Dominator boiler with copper heat exchanger is
105 GPM, 6.6 L/s. The cupro-nickel heat exchanger
allows for 120 GPM, 7.6 L/s.
An adjustable pump delay is available as a feature of
the staging controller. The pump delay establishes water
fl ow through the boiler and heating system before the
appliance starts. Consult the staging controller manual
for further details.
Low Water Cutoff
If a boiler is installed above any radiation elements it
must be fi tted with a low water cutoff device.
Refer to wiring diagram supplied with the boiler/water
heater for proper wiring connections.
DOMINATOR INSTALLATION AND OPERATION INSTRUCTIONS
Supply Return
2 1/2" NPT
Expansion Tank & Air Separator
An expansion tank or other means to control thermal
expansion must be installed in the heating system. An
expansion tank must be installed close to the boiler on
the suction side of the pump. An air scoop and automatic
air vent must also be installed to eliminate air trapped
in the system.
Primary/Secondary Piping
Boilers connected to heating systems using zone valves,
zone pumps, or systems that have excessive fl ow rates
or return water temperatures less than 125°F, 52°C
must be isolated from these systems to protect the boiler.
Variable Water Flows
Figure 11 shows a typical primary/secondary piping
system. A dedicated pump is used to maintain a
constant water fl ow through the boiler. This secondary
pump is sized to overcome the head loss of the boiler
and secondary piping system while supplying the fl ow
rate required to maintain the desired temperature rise
across the boiler. The primary pump is sized to provide
the required fl ow to the heating system. The secondary
piping connections to the primary system piping must
not be more than 12 in, 305 mm apart to ensure zero
pressure drop in the primary system, see Figure 11.
Low Return Water Temperatures
To prevent the problems associated with condensation
of the products of combustion due to low return water
temperatures a primary/secondary piping system with
a bypass and bypass valve must be installed, see Figure
12. The bypass and bypass valve must be sized the
same as the secondary piping. A balancing valve must
also be installed in the supply side of the secondary
piping downstream of the bypass. The balancing valve
should be adjusted to diver t some of the heated
discharge water into the return water until the required
inlet water temperature is achieved. The primary and
secondary pumps should be sized to provide the
required flow through each system. The secondary
piping connections to the primary system piping must
not be more than 12 in, 305 mm apart to ensure zero
pressure drop in the primary system, see Figure 12.
Multiple Boiler Systems
Systems using multiple boilers can also be installed
using a primary/secondary manifold system, Figure 13.
Piping For Use With Cooling Units
The boiler, when used in connection with a refrigeration
system, must be installed so the chilled medium is piped
in parallel with the boiler. Appropriate valves must be used
to prevent the chilled water from entering the boiler.
When a boiler is connected to a heating coil that may
be exposed to refrigerated air from an air handling
device, the piping system must be equipped with fl ow-
control valves or some other automatic means of
preventing gravity circulation of the boiler water during
the cooling cycle.
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