UP TO 88% EFFICIENT, HOT WATER SUPPLY BOILER WITH MODULATING FIRE 4:1 TURNDOWN
SUGGESTED SPECIFICATION
The gas-fired hot water supply boiler(s) shall be A. O. Smith VF Boiler model VW______ having an input rating of _______
BTU/hr and capable of supplying no less than ______ GPH at a 100°F temperature rise when fired with (Natural/Propane)
gas. 1) The boiler shall bear the ASME “H” stamp and shall be National Board registered (CRN in Canada) for 160 PSI
working pressure. 2) The boiler(s) shall be equipped with a factory-installed 125# PSIG ASME Pressure Relief Valve. 3) The
boiler(s) shall be design-tested and certified to the ANSI Z21.13 standard and approved by CSA International. 4) Meet or
exceed the SCAQMD Rule 1146.2 for low-NOx emissions and air quality standards.
The heat exchanger shall: 1) Incorporate a vertical straight tube 2 pass copper fin tube heat exchanger design. 2) Be circular,
encompassing the entire burner and forming the combustion chamber. 3) The tubes shall be rolled into ASME grade steel
glass lined tube sheets. 4) The headers shall be ASME 160 psi welded glass lined steel. 5) For ease of service and access,
headers shall be bolted and sealed to the tube sheets with silicone “O” rings, having a temperature rating of over 400°F. Tube
access plugs are not acceptable. 6) To provide rust-resistant operation, all internal heat exchanger water contact surfaces
shall be copper or glass lined steel. 7) The heat exchanger shall be immune to thermal shock. 8) All non-heating surface heat
exchanger components (headers, tube sheets, header bolts and gaskets) shall be outside and away from the combustion
and flue collection areas, only the copper fin tubes shall be exposed to the products of combustion. 9) The sealed heat
exchanger flue collection system shall be constructed of AL29-4C stainless steel that is immune to corrosive flue gases.
10) The heat exchanger shall be approved for inlet water temperatures down to 120°F. 10) The entire heat exchanger shall
carry a five (5) year warranty.
Boiler Pump: 1) The hot water supply boiler(s) shall be supplied with a factory sized and wired all bronze circulating pump.
2) The pump shall be interfaced with and managed by the boiler’s control and cycled as needed for most efficient operation.
Burner: 1)The gas burner shall be constructed of high temperature stainless steel and utilize a woven metal fiber mesh
covering, be warranted for 5 years, and fire in a radial 360-degree flame pattern. 2) The burner shall be capable of infinitely
modulating between 25% and 100% fire (4:1 turndown) with smooth starts and clean combustion.
Boiler Controls: 1) All electrical boiler functions shall be controlled, operated, and monitored by a microprocessor-based
control. 2) The microprocessor shall control and modulate the burner based on current system output requirements to
maintain the boiler set point temperature and be accurate to within plus or minus 1°F. 3) The hot surface ignition system shall
employ a separate flame sensor for maximum reliability. 4) The boiler control shall provide on board diagnostics with digital
singular fault code read outs in plain English and help screens for additional troubleshooting assistance if needed. 5) The
boiler shall be supplied with a remote tank thermistor for sensing and controlling the hot water storage tank temperature up
to 1,000 feet away. 6) Provisions for connecting a remote thermistor, alarm bell, and alternate temperature controller must be
provided. 7) Factory mounted and wired flow switch, blower prover, and blocked flue switches shall be provided. 8) The gas
train shall meet or exceed the requirements of ANSI Z21.13 and include gas pressure regulator, manual gas cock, redundant
safety gas valve, operating control valve, and plugged pressure test tapings. 9) The ASME rated pressure relief shall be
factory installed.
Venting: 1) The boiler shall be certified for direct horizontal through-the-wall venting or direct vertical venting; in addition to
sidewall or conventional vertical venting. 2) The boiler shall be capable of horizontal sidewall or direct venting up to 70
equivalent feet without the aid of any optional sidewalll vent fans or blowers.
Factory Start-up: 1) The boiler manufacturer must supply complete factory start-up by a factory approved start-up agent.
The boiler shall comply with ASHRAE/IESNA 90.1-1999 standards.
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ACGSS02307
Page 4 of 4
500 Tennessee Waltz Pkwy, Ashland City, TN 37015
For Technical Information and Automated Fax Service, call 800-527-1953.
A. O. Smith reserves the right to make product changes or improvements without prior notice.
©2007 A. O. Smith Corporation
Printed in U.S.A.
www.hotwater.com
