Crown Boiler AWR Series Installation Instructions Manual page 19

10) Drain Valve - The drain valve is shipped in the boiler parts bag. Install it in the 3/4" tapping on the left side of the
boiler as shown in Figure 2.1. Alternatively the drain valve can also be located in an installer supplied tee at the return
connection.
11) Alternate Return Tapping - An unplugged 1-1/4" return tapping is provided on the left side of the boiler (see "Piping
for Special Situations" below). Use the nipple and cap provided to plug whichever return tapping is not used. Both the
supply and return connections must be made on the same side of the boiler.
Certain types of heating systems have additional requirements. Some of the more common variations follow:
1) "Left Piped" Boilers – If necessary, the supply and return may be connected to the left side of the boiler by moving the
1-1/4" cap and the relief valve fittings from the tappings in the left side of the boiler to the corresponding tappings on the
right. Both the supply and return connections must be made on the same side of the boiler.
2) Indirect Water Heaters - Figure 7.4 shows typical indirect water heater piping. Boiler piping is the same as for any two-
zone system. Figure 7.4 shows circulator zoning, which is usually preferred for indirect water heaters. Size the circulator
and indirect water heater piping to obtain the boiler water flow through the indirect water heater called for by the indirect
water heater manufacturer.
3) Large Water Volume Systems - The piping shown in Figure 7.5 will minimize the amount of time that the boiler operates
with return temperatures below 120°F on these systems. A bypass is installed as shown to divert some supply water
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 first 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 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 this one, such as four
way mixing valve and variable speed injection pumping 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 7.6.
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 7.7. 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.
Oxygen contamination of boiler water will cause corrosion of iron and steel boiler components and can lead
to boiler failure. Warranty does not cover problems caused by oxygen contamination of boiler water or scale
(lime) build-up caused by frequent addition of water.
Piping for Special Situations
!
WARNING
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