Crown Boiler AWR070 Installation Instructions Manual page 20

4) 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 AWR. These systems also typically have return
temperatures well below the 120°F minimum.
Figure 14 illustrates the use of a heat exchanger to connect the AWR boiler to this type of 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 the non-condensing boilers like the AWR such as four
way mixing valve and variable speed injection Circulatoring systems.
5) Systems containing oxygen - Many hydronic systems contain enough dissolved oxygen to cause severe corrosion damage
to a cast iron boiler such as the AWR. 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 8.6.
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 Circulator and expansion tank, must be
designed for use in oxygenated water.
6) Piping with a Chiller - If the boiler is used in conjunction with a chiller, pipe the boiler and chiller in parallel as shown in
Figure 8.7. Use isolation valves to prevent chilled water from entering the boiler.
7) 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 8.7: BOILER PIPING WITH CHILLER
18