Heating System Piping - RBI Series 8800 Installation And Operation Manual

SERIES 8800 & 8900 INSTALLATION AND OPERATING INSTRUCTIONS
Flow Switch
The flow switch supplied with the boiler/water heater
must be wired to the terminal strip in the junction box
to prevent the boiler from firing unless there's adequate
water flow through the unit. The flow switch must be
installed in the supply piping adjacent to the boiler outlet
connection.
CAUTION: Failure to properly install the flow switch
may result in damage to the boiler/water heater heat
exchanger voiding the warranty!

HEATING SYSTEM PIPING

General Piping Requirements
All heating system piping must be installed by a qualified
technician in accordance with the latest revision of the
ANSI/ASME Boiler and Pressure Vessel Code, Section
IV, and 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" 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 supporting the system. A minimum system
pressure of 12 psig must be maintained.
Heating Boiler Piping Connections
The supply and return connections should be sized to
suit the system, see Table 4.
Table 4 - Supply & Return Pipe Sizing
Boiler Model Supply Size (in)
8900 2 1 / " NPT
2
8800 3" Victaulic
*Models 420-950 may have 2
installed.
Pump Requirements
This low mass boiler requires a continuous minimum
water flow 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 5 provides the heat exchanger
pressure drop and temperature rise figures. The
temperature rise across the boiler must never
exceed 30°F (17°C). The pump should be wired to run
continuously unless the optional pump delay is installed.
The pump delay turns the pump on each time the
burners fire and runs the pump for 100 seconds after
the call for heat is satisfied.
Return Size (in)
2 1 / " NPT
2
3" Victaulic
1 / " x 2" reducing fitting
2
CAUTION: A temperature rise outside of the range
listed in Table 5 indicates that the flow rate through
the heat exchanger is incorrect which will damage
the heat exchanger voiding the warranty! The
maximum allowable flow rate through an 8900 boiler
is 100 GPM, 200 GPM for an 8800. If higher flow rates
are required the optional Cupro-Nickel heat
exchanger should be considered.
Low Water Cutoff
If a boiler is installed above any radiation elements it
must be fitted with a low water cutoff device.
Expansion Tank
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.
Primary/Secondary Piping
Boilers connected to heating systems using zone valves,
zone pumps, or systems that have excessive flow rates
or return water temperatures less than 110 °F (43°C)
must be isolated from these systems to protect the
boiler.
Variable Water Flows
Figure 1 shows a typical primary/secondary piping
system. A dedicated pump is used to maintain a
constant water flow through the boiler. This secondary
pump is sized to overcome the head loss of the boiler
and secondary piping system while supplying the flow
rate required to maintain the desired temperature rise
across the boiler. The primary pump is sized to provide
the required flow to the heating system. The secondary
piping connections to the primary system piping must
not be more than 12" apart to ensure zero pressure drop
in the primary system, see Figure 1.
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
2. 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 divert 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"
apart to ensure zero pressure drop in the primary
system, see Figure 2.
Page 7