A.O. Smith 750 manual

1 W ARNING: If the information in this manual is not followed exactly , a fire or explosion may result causing property damage, personal injury or loss of life. — Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or any other appliance. — WHA T TO DO IF YOU SMELL GAS: • Do not try to light any applianc[...]

2 SAFE INST ALLA TION, USE AND SERVICE Y our safety and the safety of others is extremely important in the inst allation, use, and servicing of this boiler . Many safety-related messages and instructions have been provided in this manual and on your own boiler to warn you and others of a potential injury hazard. Read and obey all safety messages an[...]

3 GENERAL SAFETY[...]

4 SAFE INST ALLA TION, USE, AND SERVICE ....................................................................................................................................... 2 GENERAL SAFETY ............................................................................................................................... .............................[...]

5 For all side wall terminated, horizontally vented power vent, direct vent, and power direct vent gas fueled water heaters installed in every dwelling, building or structure used in whole or in p art for residential purposes, including those owned or operated by the Commonwealth and where the side wall exhaust vent termination is less than seven ([...]

6 CONNECTION DIAGRAM[...]

7[...]

8 SCHEMA TIC DIAGRAM VB/VW-500, 750 & 1000 SCHEMA TIC DIAGRAM[...]

9 LIGHTING & OPERA TION INSTRUCTIONS FOR MODELS VB/VW 500, 750 AND 1000:[...]

10 children to use a hot water t ap, or to draw their own bath water . Never leave a child or disabled person unattended in a bathtub or shower . The boiler should be located in an area that is inaccessible to the general public. T ABLE 1. Risk of Scalds. T emperature Time to Produce 2nd & 3rd Setting Degree Burns on Adult Skin Over 170°F (77?[...]

11 sequences and safety features associated with a gas ignition control system. The system continuously performs various diagnostic test s to verify proper appliance and control operation. Should an unsafe condition occur , the control will shut down the burner and display a red service light as well as indicate the cause of the error on the displa[...]

12 the temperature is less than the operating setpoint minus the differential temperature and the thermostat input is closed then a call for heat is established and the system shift s to the run mode (green "Running" LED turns on). 5. The heating sequence begins by applying power to the pump. 6. After a few seconds the blower is turned on[...]

13 waits for a heat request (determined by the Thermost at or controlling probe input s). All outputs are o f f i n this st ate except that if the Post-Circulate time i s set to continuous, th e pump will be on. When the heat request i s received, the system moves to the Pre-Circulate state. • Pre-Circulate: The yellow LED is turned off and the g[...]

14 if the blower prover does not activate after 15 seconds. This time allows the blower relay to activate, the blower to come up to speed, and the response from the blower prover to be filtered. • User Settings Screen: Each setpoint or user setting has either a limited selection of values, or a limited range of values. The Up/Down keys are used t[...]

15 kBtu rating of the boiler (0 to 5750kBtu in 10kBtu increments) The sof tware revision level of the MCB. • Current Error Screen: Displays the last error that the system has detected plus a time stamp of when the error occurred. (The time st amp is based on the elapsed hours value at the time the error occurred. It is displayed in hours and minu[...]

16 TROUBLESHOOTING IGNITION SYSTEM Fault Messages and Lockout S tatus (* = stage number: 1, 2, 3, or 4) FAUL T DISPLA YED DESCRIPTION RED LED LOCKOUT “Display Fail” Communications with UIM interrupted Continuous Auto Reset Check communication cable to UIM. T ry moving to other Internal Communications connector on MCB. Also check the connectors [...]

17 This is a pre-mix burner system. The flame is not supposed to be directly on the burner . The flame should be just above the burner deck approximately 1/8” and blue in color , see illustration. BURNER FLAMES Visually check flame characteristics through the view port located on the top head of the boiler . The “Burner Flames” illustration s[...]

18 Any safety devices including low water cutoffs used in conjunction with this boiler should receive periodic (every six months) inspection to assure proper operation. A low water cutoff device of the float type should be flushed every six months. Periodic checks, at least twice a year , should be made for water leaks. More frequent inspections ma[...]

19 lines with air or water and clear or replace the blocked portions of the line as necessary . Note that areas of the drain line which include a sag or low spot in the line will also form a condensate trap which can be removed by levelling the tube and does not indicate a blocked system. Inspect the metal vent drain and vent collector drain connec[...]

20 NOTES[...]

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22 NOTES[...]

23 LIMITED W ARRANTY A. O. Smith Corporation, the warrantor , extends the following LIMITED WARRANTY to the owner of this boiler: 1. If within TEN years after initial inst allation of the boiler, a heat exchanger or gas burner shall prove upon examination by the warrantor to be defective in material or workmanship, the warrantor , at his option wil[...]

24 500 T ennessee W altz Parkway , Ashland City , TN 37015 Phone: 800-433-2545 w w w .hotwater .com E-Mail: p art s@hotwater .com[...]