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Boiler installation considerations, Hydronic system – A.O. Smith 3400 User Manual

Page 15

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15

GENERAL

If the system is to be filled with water for testing or other purposes

during cold weather and before actual operation, care must be taken

to prevent freezing of water in the system. Failure to do so may cause

the water in the system to freeze with resulting damage to the system.
Damage due to freezing is not covered by the warranty.
Figure 75 on Page 78 shows a typical primary, secondary piping

method. This is the preferred piping method for most stainless steel

boilers. Other piping methods, however, may provide good system

operation. A prime concern when designing heating systems is the

maintenance of proper flow through the unit during boiler operation.

The secondary pump should be sized per the recommended flow

rate of the boiler, see Dimension and Capacity Data section in this

manual.
Before locating the boiler:
1. Check for nearby connection to:

• System water piping
• Venting connections
• Gas supply piping
• Electrical power

2. Locate the boiler so that if water connections should leak,

water damage will not occur. When such locations cannot

be avoided, it is recommended that a suitable drain

pan, adequately drained, be installed under the boiler.

The pan must not restrict combustion air flow. Under no

circumstances is the manufacturer to be held responsible

for water damage in connection with this boiler, or any of its

components.

3. Check area around the boiler. Remove any combustible

materials, gasoline and other flammable liquids.

4. Make sure the gas control system components are protected

from dripping or spraying water or rain during operation or

service.

5. If a new boiler will replace an existing boiler, check for and

correct system problems, such as:
• System leaks causing oxygen corrosion or heat

exchanger cracks from hard water deposits.

• Lack of freeze protection in boiler water causing system

and boiler to freeze and leak.

HYDRONIC SYSTEM

The following is a brief description of the equipment required

for the installations noted in this manual. All installations must

comply with local code.
WATER SUPPLY LINE
These boilers can be used only in a forced circulation hot water

heating system. Since most forced circulation systems will be of

the closed type, install the water supply line as shown on piping
diagram.
Fast filling of large pipe, old radiator installations and pressure

purging of series loop systems (where high pressures are not

available) requires bypassing of the pressure reducing valve.
Gener ally, pressure purging is not possible with a well pump

system. High point air venting is essential.

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 manu ally 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 ensure avoidance of potential damage to the

boiler which may not be covered by the warranty.
EXPANSION TANK
If the system is of the closed type, install an expansion tank. The

sizing of the expansion tank for a closed system is very important and

is directly related to the total water volume of the system.
An air separator as shown in the piping diagrams is recommended

especially for modern commercial hydronic systems. See Figure 75

on Page 78.
VENT VALVES
It is recommended that automatic, loose key or screw-driver 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 maximum pressure drop for sever al

circuits, manifolds should be larger than system mains.
The circuits should be spaced on the heater at a minimum of 3”

(76 mm) 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

circulating pumps. 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.
CHECK VALVES
Check valves must be installed to isolate each boiler in

installations where multiple boilers/pumps are installed in the

same zone.
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 flow control valves, manual or

motorized, must be provided to prevent the chilled medium from

entering the boiler.
If the boiler is connected to chilled water piping or its heating coils

are exposed to refrigerated air, the boiler piping system must be

equipped with flow 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 so much more than heating flow rates. In this way each

system (heating or cooling) is circulated independently.

BOILER INSTALLATION CONSIDERATIONS

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