Crown Aruba 5 Installation Manual

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directly into the return water. The bypass pipe should be the same size as the supply. The two throttling valves shown are
adjusted so that the return temperature rises above 120°F during the rst few minutes of operation. A three-way valve can
be substituted for the two throttling valves shown. If the circulator is mounted on the supply, the bypass must be on the
discharge side of the circulator.
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 boiler. These systems also typically have return
temperatures well below the 120°F minimum.
Figure 8.6 illustrates the use of a heat exchanger to connect the 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 ow 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
ll 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 this one, such as four
way mixing valve and variable speed injection Circulating systems.
5) Systems containing oxygen - Many hydronic systems contain enough dissolved oxygen to cause severe corrosion damage
to a cast iron boiler such as this one. 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 ow 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 ow 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