RBI SERIES 8800 Installation & Operation Manual page 12

Page 12
Low Water Cutoff
If a boiler is installed above any radiation elements it
must be fitted with a low water cutoff device.
Refer to the wiring diagram supplied with the boiler/
water heater for proper wiring connections.
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 7 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 in, 305 mm apart to ensure zero
pressure drop in the primary system, see Figure 7.
SERIES 8800 & 8900 INSTALLATION AND OPERATING INSTRUCTIONS
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 8. 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 in, 305 mm apart to
ensure zero pressure drop in the primary system, see
Figure 8.
Multiple Boiler Systems
Systems using multiple boilers can also be installed
using a primary/secondary manifold system, Figure 9.
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 flow-
control valves or some other automatic means of
preventing gravity circulation of the boiler water during
the cooling cycle.