RBI LCD Series Installation & Operation Manual page 15

CAUTION: A temperature rise outside of the range
listed in Table 6 indicates that the flow 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 LCD
boiler with copper heat exchanger is 92 GPM,
5.8 L/s on 225-1200 models and 115 GPM, 7.3 L/s
on 1480 to 2300 models. The cupro-nickel heat
exchanger allows for 100 GPM, 6.3 L/s on 225 to
1200 models and 125 GPM, 7.9 L/s on 1480 to 2300
models.
Low Water Cutoff
If a boiler is installed above any radiation elements it
must be fitted with a low water cutoff device.
Refer to wiring diagram supplied with the boiler/water
heater for proper wiring connections.
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 flow 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 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 11.
LCD INSTALLATION AND OPERATION 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
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 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 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 flow-
control valves or some other automatic means of
preventing gravity circulation of the boiler water during
the cooling cycle.
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