Crown Boiler TWB Series, Installation Instructions Manual

Page: 24 / 56

22
3) Low Temperature Systems - Some systems, such as radiant tubing systems, require the system water temperature to
be limited to a value below the temperature of the water leaving the boiler. These systems also typically have return
temperatures well below the 120°F minimum.
Figure 8.4 illustrates the use of a heat exchanger to connect this boiler to such a system. The heat exchanger will permit
the transfer of heat from the boiler water to the low temperature system while holding the system supply and boiler return
temperatures within their limits. For this system to work properly, the heat exchanger must be properly sized and the
correct flow rates are required on either side of the heat exchanger. Consult the heat exchanger manufacturer for sizing
information. The water in the boiler is completely isolated from the water in the system. This means that separate fill and
expansion tanks are required for the heating system loop.
There are several other ways to connect low temperature systems to non-condensing boilers such as four way mixing
valves and variable speed injection pumping systems.
4) Systems containing oxygen - Many hydronic systems contain enough dissolved oxygen to cause severe corrosion damage
to a cast iron boiler. Some examples include:
• Radiant systems that employ tubing without an oxygen barrier.
• Systems with routine additions of fresh water.
• Systems which are open to the atmosphere.
If the boiler is to be used in such a system, it must be separated from the oxygenated water being heated with a heat
exchanger as shown in Figure 8.4.
Consult the heat exchanger manufacturer for proper heat exchanger sizing as well as flow and temperature requirements.
All components on the oxygenated side of the heat exchanger, such as the pump and expansion tank, must be designed for
use in oxygenated water.
5) Air Handlers - Where the boiler is connected to air handlers through which refrigerated air passes, use flow control valves
in the boiler piping or other automatic means to prevent gravity circulation during the cooling cycle.
FIGURE 8.4: ISOLATION OF BOILER FROM SYSTEM WITH A HEAT EXCHANGER