UNDESIRABLE OPENINGS, CAUSING POOR COMBUSTION. SOOTING MAY RESULT WITH AN INCREASED RISK OF ASPHYXIATION.

THERMAL EXPANSION (CLOSED SYSTEM)

Thermal expansion occurs in any hot water system when system water is heated or “recovered” during periods of non-use.

If the system is operated in an “open” condition such as being connected directly to the city main, the volume of expanded water generated during the recovery periods can be dissipated back through the “open” connection to the city main so pressure cannot increase.

However, once a back flow preventer is installed to isolate system water from the public supply; or a pressure reducing valve is installed to protect a water meter; or any device preventing flow back into the cold water supply, the “open” condition becomes “closed”. During periods of temperature recovery and no usage, water expands and the pressure increases until a relief valve opens spilling hot water.

A relief valve opening on pressure will flow small amounts of water, whereas relieving on temperature releases large amounts of water. Consult the section under “High Water Temperature” to determine the cause of the relief valve to open due to temperature.

Since the water is not compressible, some provision must be made for THERMAL EXPANSION to protect the system from excessive pressures. Two options are:

1.Install an expansion tank properly and adequately sized for the expanding volume of water.

2.Install a pressure relief valve in the cold water supply line having a setting of at least 10lbs. below the system working pressure, located at or near a suitable drain. This valve will open at each heat cycle when there is no hot water demand on the system.

Service problems or parts failure due to excessive pressure are NOT covered under warranty.

The pressure and temperature relief valve supplied with the water heater IS NOT considered to be protection against thermal expansion.

VENTING

WARNING

THE INSTRUCTIONS IN THIS SECTION ON VENTING MUST BE FOLLOWED TO AVOID CHOKED COMBUSTION OR RECIRCULATION OF FLUE GASES. SUCH CONDITIONS CAUSE SOOTING OR RISKS OF FIRE AND ASPHYXIATION.

Heater must be protected from freezing downdrafts during shutdown periods.

Remove all soot or other obstructions from chimney, which will retard free draft.

Venting materials used for this category 1 appliance must be in accordance with the National Fuel Gas Code and all state and local requirements.

NOTE: A NEGATIVE DRAFT MUST BE MAINTAINED IN VENT PIPING (-0.02 to -0.06).

VENT CONNECTOR

The chimney vent connector diameter should be the same size as the heater flue outlet, see table 1. A minimum rise of 1/4” per foot of horizontal connector length must be maintained between the heater and chimney opening, fig. 2. The connector length should be kept as short as possible.

TABLE 1

BTP/BTPD/BTPN/COF/COBT

FLUE OUTLET

INPUT (KBTUh)

(INCHES)

140,

199

5

255, 270, 300

6

400

7

540,

600

8

720, 800, 1000

10

1250,

1500

12

1750,

2000

14

2250,

2500

16

BAROMETRIC DRAFT CONTROL ASSEMBLY

A double-acting barometric draft control assembly is provided with each unit. This assembly must be attached to the heater as shown in figure 2. The direction in which the outlet to the draft control assembly faces is arbitrary. This assembly must be fitted to the jacket cover such that it is plumb and level to the ground. Fasten the draft control assembly to the top cover using sheet metal screws at three locations, or more, as required.

Refer to the instructions provided with the barometric damper for complete installation requirements.

Dampers or other obstructions must not be installed between the heater and the barometric draft control assembly.

Barometric draft control counterweights can be adjusted for installation conditions by an authorized A.O. Smith Start-Up Agent. Any readjustment must be by authorized A.O. Smith Start-Up agent.

PROPER DRAFT CONTROLLER AND

VENT PIPE INSTALLATION - FIGURE 2

VENT CONNECTION

Vent connections must be made to an adequate stack or chimney. Refer to the National Fuel Gas Code or to the vent pipe manufacturer’s gas vent and chimney sizing table to properly design and size the venting system. Refer to Table 2 for the vent pipe size required for installation to the barometric draft control assembly outlet.

6

Page 5 Page 7
Page 6
Image 6
A.O. Smith COBT, COF, BTPN Thermal Expansion Closed System, Venting, Vent Connector, Barometric Draft Control Assembly
Page 5 Page 7

BTP-140-140, BTPN, BTP-140-140 thru 600-2500, COF, COBT specifications

A.O. Smith, a renowned leader in water heating technology, offers a range of high-efficiency commercial boilers, including the COBT, BTP-140-140 through BTP-600-2500, BTPN, and COF models. Designed to cater to diverse heating needs, these systems are engineered for optimal performance, reliability, and efficiency, making them ideal for various applications, from hospitality to industrial processes.

The A.O. Smith COBT model stands out for its innovative features, such as a fully modulating burner that adjusts output based on demand, enhancing energy efficiency and ensuring consistent comfort. Its compact design allows for easy installation in limited spaces, while robust construction materials ensure longevity. The integrated controls offer real-time monitoring and diagnostics, allowing operators to maintain peak performance and reduce maintenance costs.

The BTP series, particularly the BTP-140-140 through BTP-600-2500, delivers high heating capabilities with a range of output options. These models feature a sophisticated heat exchanger design that maximizes heat transfer efficiency while minimizing energy consumption. The use of dual-fuel capability provides flexibility, allowing users to switch between natural gas and propane, thus enhancing operational resilience. The BTP units are also equipped with advanced modulating burners that adapt to varying load conditions, further optimizing fuel usage.

For applications requiring enhanced performance, the BTPN models offer additional features like integrated pumps and a larger footprint for increased capacity. This makes them ideally suited for high-demand environments where consistent hot water supply is critical. The COF model complements this lineup, focusing on oil-fired applications and delivering reliability across diverse operating conditions.

In terms of technology, A.O. Smith utilizes cutting-edge combustion systems and advanced control technologies that not only enhance efficiency but also meet stringent emission standards. The incorporation of condensing technology in many models enables users to harness latent heat from flue gases, significantly improving overall system efficiency.

Overall, A.O. Smith's COBT, BTP, BTPN, and COF models are engineered with a commitment to quality, efficiency, and user-friendliness. Their reliability, advanced technologies, and versatile applications make them a preferred choice for businesses looking for durable and efficient heating solutions. Whether for commercial or industrial needs, A.O. Smith continues to set the standard for water heating systems.
Top Page Image Contents