A.O. Smith VB/VW- 1000 System installation, General, Hot Water Heating Hydronic Equipment

system installation

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 a downdraft entering the boiler or freezing air from contacting 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.

Good practice requires that all heavy piping, etc., be support­ed.

Figure 13 shows a typical primary, secondary piping method. This is the preferred piping method for most copper fin tube 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 in this manual.

A system bypass should be installed, as shown in Figure 13, to prevent boiler circulation starvation when the system zones call for reduced flow.

This bypass may also be used with multiple boilers manifolded for reverse-return flow. This system bypass would be installed from boiler outlet to suction side of pump.

Hot Water Heating (Hydronic) Equipment

The following is a brief description of the equipment required for the installations noted in this manual. All installations must comply with local code.

1.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, see Figure 13.

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.

Generally,­ 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 manually­ operated valve. An overhead surge tank is required. A minimum pressure of 15 psi (100kPa) 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.

2.EXPANSION TANK

If the system is of the closed type, install an expansion tank as shown in Figure 13. 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. Refer to “Systems and Equipment” volume of the ASHRAE handbook.

An air separator as shown in the piping diagrams is recom­ mended especially for modern commercial hydronic systems.

3.VENT VALVES

It is recommended that automatic, loose key or screw- driver type vent valves be installed at each convector or radiator.

4.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 several­ circuits, manifolds should be larger than system mains.

The circuits should be spaced on the heater at a minimum of 3” (76mm) 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.

5.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.

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 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.

6.CIRCULATING PUMP

FOR HOT WATER HEATING BOILERS - VB MODELS, the circulating pump is NOT provided and must be field-installed.

NOTE: If a system pump is to be installed on a VB model, the maximum rating of the pump motor must not exceed 1 hp.

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