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16
HYDRONIC INSTALLATION
The following is a brief description of the equipment required for
installations noted in Figure 10. All installations must comply with
local codes.
TABLE 14: INSTALLATION ITEMS
NO. SUGGESTED ITEMS FOR INSTALLATION
1. PAIR OF SHORT PIPE NIPPLES, PAIR OF BOILER
LOOP TEES AND BALL VALVE BETWEEN SYSTEM
SUPPLY AND RETURN - ONE SET PER EACH BOILER
2. BOILER PIPE LOOP (See Table 5.)
3. BOILER CIRCULATING PUMP (See Table 5.)
4. THERMOMETER
5. PRESSURE GAUGE
6. LOW WATER CUTOFF (If Required By Local Code.)
7. FLOW SWITCH (Factory-Installed)
8. PRESSURE RELIEF VALVE (Factory-Installed)
9. BOILER INLET - OUTLET
10. SYSTEM SUPPLY TEMPERATURE THERMOMETER
11. DRAIN or BLOW-DOWN VALVE
WATER SUPPLY LINE
These boilers can be used ONLY in a forced circulation hot water
heating system. The pump must be interlocked with the boiler to
prevent boiler operation without water circulation. See maximum
and minimum flow rate information. Since most forced circulation
systems will be of the closed type, install the water supply line as
shown on piping diagram. See Figure 10. Severe damage will
occur if the boiler is operated without proper water flow
circulation.
Fast filling of large pipe, old radiator installations (where high
pressures are not available) requires bypassing of the pressure
reducing valve. Generally, pressure purging is not possible with a
well pump system. High point air venting is essential. For details,
refer to OPERATION section of this manual. If the system is of the
open type, a pressure reducing valve will not be required as the
water supply to the system will be controlled by a manually operated
valve. An overhead surge tank is required.
A MINIMUM PRESSURE
OF 15 PSI (100 kPa) MUST BE MAINTAINED ON THE BOILER AT
ALL TIMES to avoid potential damage to the boiler that may not be
covered by the warranty.
CONVENTIONAL SPACE HEATING INSTALLATION
Modern copper-finned tube type boilers are exceptionally fast heating
units. The low water volumes in relation to firing rates require special
attention to water flow rates for smooth, efficient operation. These
considerations for the A. O. Smith copper heat exchanger boilers
are covered below.
Refer to Table 5 showing flow rate vs. pressure drop and
temperature rise.
Figure 10 shows a typical installation of the boiler.
A system with several flow controlled zones, or with a 3-way mixing
valve system could present a flow rate to the boiler of less than
required for a maximum of 50°F (28°C)
temperature rise. Design
system with compensating bypasses to the boiler.
A system bypass should be installed as shown in Figure 10 to
prevent boiler circulation starvation when the system zones call for
reduced flow.
volume may result in condensation within the boiler on cold starts.
This condensing of water vapor in the combustion area can be
prevented if a portion of the system water flow is diverted past the
boiler to cause an increase in boiler temperature.
BYPASS BALANCING
With systems where water temperature can be expected to drop
appreciably due to long standby periods, or heavy draw down, a
bypass pipe of at least 1" size with a balancing cock should be
installed between the boiler inlet and outlet. See Figure 10. When
the system first starts, the valve should be slowly opened until the
condensing ceases. This adjustment remains at a permanent
setting to establish required temperature rise across the boiler.
AIR SEPARATOR
An air separator as shown in the piping diagram is recommended
especially for modern commercial hydronic systems.
VENT VALVES
It is recommended that automatic, loose key or screwdriver type
vent valves be installed at each convector or radiator.
SYSTEM HEADERS
Split systems with individual supply and return lines from the boiler
room should normally have this piping connected to supply and
return manifold headers near the boiler. To achieve good water
distribution with minimum pressure drop for several circuits,
manifolds should be larger than system loops.
The circuits should be spaced on the header at a minimum of
3" (7.6 cm) center to center. Install a balancing cock in each return line.
Manifold headers are recommended for split systems with or
without zone valves and also those installations with zone
circulators. If the system is to be split at remote points, good practice
requires special attention be given to main pipe sizing to allow
balancing of water flow.
COOLING PIPING
When the boiler is used in conjunction with a refrigeration system
it must be installed so that the chilled medium is piped in parallel
with the boiler. Appropriate valves, manual or motorized, must be
provided to prevent the chilled medium from entering the boiler.
Water temperature in the heating system must be reduced to less
than 100°F (38°C) before cooling system is started, or damage to
the chiller unit may occur.
If the boiler is connected to chilled water piping or heating coils
exposed to refrigerated air, the boiler piping system must be
equipped with flow control valves or other automatic means to
prevent gravity circulation through the boiler during the cooling cycle.
Primary/secondary pumping of both the chiller(s) and the boiler(s)
is an excellent winter-summer change-over method, because
cooling flow rates are much more than heating flow rates. In this
way each system (heating or cooling) is circulated independently.
EXPANSION TANK
Install an expansion tank as shown in Figures 10, 11, and 13. The
sizing of the expansion tank is very important and is directly related
to the total water volume of the system. Refer to ASME or other
reliable specifications for sizing.