A.O. Smith 750 SERIES manual

1 A DIVISION OF A. O. SMITH CORPORA TION MC BEE, SC., RENTON, WA., STRA TFORD-ONT ARIO, VELDHOVEN-THE NETHERLANDS w w w .hotwater .com GAS-FIRED COMMERCIAL COPPER BOILERS FOR HYDRONIC HEA TING AND HOT W A TER SUPPL Y USER'S INFORMA TION MANUAL GB/GW-300, 400, 500, 650, 750 SERIES 400, 401, 402, 403, 404, 405, 2-ST AGE UNITS W ARNING Should ove[...]

2 Lighting Instructions for the G(B/W) 300 through 750 models THE UNIT SHOULD NOT BE INST ALLED DIRECTLY ON A CARPETED FLOOR. A FIRE HAZARD MA Y RESUL T . Instead, the boiler must be installed on the A. O. Smith Combustible Floor Kit Base or concrete blocks extending beyond the full width and depth of the boiler by at least 3 (76.2mm) inches. If th[...]

3 LIGHTING INSTRUCTIONS These models have an automatic hot surface ignition system mounted on the combustion chamber panel inside the front jacket. This hot surface igniter ignites the main burner gas whenever the system control calls for heat. Before proceeding with operation of the unit, make sure the boiler and system are filled with water and a[...]

4 the surrounding air pressure. Inspection of the boiler and vent system is necessary to insure that flue gas leakage to the surrounding area does not occur . Inspect the external surfaces of the vent system every 3 months for corrosion and leakage. Inspect the vent terminations for corrosion and foreign matter which may be blocking the exhausting [...]

5 Figure 1A. CCB (Drawing #211758)[...]

6 Figure 1B. FCB (Drawing #211759)[...]

7 Figure 1C. PDB (Drawing #211760)[...]

8 closed and everything else is in the proper state, a "call for heat" condition will be initiated. These leads should be shorted together, when a thermostat is not being used. If it is desired that the thermostat control the temperature of the boiler , the operating setpoint of the system should be set higher than the temperature that th[...]

9 CCB - Three position Dipswitch (Flame Control Section): This dipswitch is similar to the FCB dipswitches described below , but with only three switches being used: the number of blower speeds (switch #3), Hi Gas option (switch #2) and a spare (switch #1). Only the blower speed selection and Hi Gas are required because FCB1 always has a blower , i[...]

10 • S tored values are recalled from memory . • Configuration dipswitches are read. • Pending faults are recalled • Micros on all boards start running (indicated by a flashing Y ellow LED near each micro) • Input sensors are read • Communications between micros and boards is established • FCB's are configurated with the number o[...]

11 The operation of these parts is described below: UIM Screens: On all screens a double vertical bar appears on the right side of the display each time a key is touched to indicate that a key has been activated. On several screens an indicator ">" appears on the left side of the display to indicate the active line. The "Up/ Down&[...]

12 except the fault states. If enabled the powered vent and the IRI gas valve are turned on. A command is sent to all active stages to cold purge the system. Cold purging clears out any combustion gas that may be in the combustion chamber . When purging is complete the system moves to the Heat S tate. • Heat St ages 1-4: The system will command t[...]

13 • 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 to change values. After changing an item, the Select key is pressed to accept the change, or the Menu key is pressed to reject the change and restore the item to its original value. The followi[...]

14 CONNECTION DIAGRAM (Drawing #21 1769) FIGURE 4.[...]

15[...]

16 Number of cycles for each stage (Number of times stage has been in heat mode). Kbtu rating of the boiler (0 to 5750Kbtu in 10Kbtu increments) The software revision level of the CCB, and FCB micro- controllers. Current Error Screen: • Displays the last error that the system has detected plus a timestamp of when the error occurred. (The timestam[...]

17 TROUBLESHOOTING IGNITION SYSTEM Fault Messages and Lockout S tatus (* = stage number: 1 or 2) Fault Displayed 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 CCB. Also check the connectors where[...]

“Blocked Flue” Flue is Blocked Continuous SOFT • Caused by the blocked flue switch contacts being open when they should have been closed. Check for flue blockage, switch contacts, wiring. “High Limit” Outlet temp. exceeded high limit setpoint Continuous Auto Reset • Caused when the temperature of the outlet probe exceeds the high limit [...]

Other troubleshooting hints: 1. Input switches can be easily checked by observing their activation on the UIM System S tatus screen. Force the boiler to remain in the S t andby mode by opening the Thermost at input or by setting the operating setpoint to the minimum so that the system does not request heat. Then short out the contacts on the switch[...]

20 NOTES[...]

21 NOTES[...]

22 NOTES[...]

23 NEW BOILER LIMITED W ARRANTY A. O. Smith Corporation, the warrantor , extends the following LIMITED W ARRANTY to the owner of this hydronic boiler: 1. If within TEN years after initial installation of the boiler , the heat exchanger shall prove upon examination by the warrantor to be defective in material or workmanship, the warrantor , at his o[...]

24 A DIVISION OF A. O. SMITH CORPORA TION MC BEE, SC., RENTON, WA., STRA TFORD-ONT ARIO, VELDHOVEN-THE NETHERLANDS w w w .hotwater .com[...]