A.O. Smith 750 SERIES User Manual
COPPER BOILERS FOR HYDRONIC
USER'S INFORMATION MANUAL
HEATING AND HOT WATER SUPPLY
SERIES 400, 401, 402, 403, 404, 405,
WARNING: 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.
—WHAT TO DO IF YOU SMELL GAS:
•Do not try to light any appliance.
•Do not touch any electrical switch; do not use any phone in your building.
•Immediately call your gas supplier from a neighbor’s phone. Follow the gas supplier’s instructions.
•If you cannot reach your gas supplier, call the fire department.
—Installation and service must be performed by a qualified installer, service agency or the gas supplier.
Should overheating occur or the gas supply fail to shut off, do not turn off or disconnect the electrical supply to the pump. Instead, shut off the gas supply at a location external to the appliance.
Do not use this boiler if any part has been under water. Immediately call a qualified service technician to inspect the boiler and to replace any part of the control system and any gas control which has been under water.
LIGHTING INSTRUCTIONS .......................................
OPERATING SEQUENCE, EMC5000 .........................
CONNECTION DIAGRAM ............................................
EMC5000 INSTRUCTIONS ......................................
TEXT PRINTED OR OUTLINED IN RED CONTAINS INFORMATION RELATIVE TO YOUR SAFETY. PLEASE READ THOROUGHLY BEFORE INSTALLING AND USING THIS APPLIANCE.
A DIVISION OFA. O. SMITH CORPORATION
MC BEE, SC., RENTON, WA.,
PLEASE KEEP THESE INSTRUCTIONS ADJACENT TO BOILER AND
NOTIFY OWNER TO KEEP FOR FUTURE REFERENCE.
PRINTED IN U.S.A. 0306
THE UNIT SHOULD NOT BE INSTALLED DIRECTLY ON A CARPETED FLOOR. A FIRE HAZARD MAY RESULT. 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 the boiler is installed in a carpeted alcove, the entire floor must be covered with concrete blocks, or use the A. O. Smith Combustible Floor Kit Base.
FLAMMABLE ITEMS, PRESSURIZED CONTAINERS OR ANY OTHER POTENTIAL FIRE HAZARDOUS ARTICLES MUST NEVER BE PLACED ON ORADJACENT TO THE BOILER. OPEN CONTAINERS OF FLAMMABLE MATERIAL SHOULD NOT BE STORED OR USED IN THE SAME ROOM WITH THE BOILER.
Light the unit in accordance with the instructions on the lighting and operating label attached to the boiler. These instructions are repeated on the following two pages.
Lighting Instructions for the G(B/W) 300 through 750 models
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 all air is expelled from the boiler, radiator tank(s) and piping.
THE MAIN MANUAL GAS
THERE IS A RISK IN USING FUEL BURNING APPLIANCES SUCH AS GAS WATER BOILERS IN ROOMS, GARAGES OR OTHER AREAS WHERE GASOLINE AND OTHER FLAMMABLE LIQUIDS ARE USED OR STORED, OR
HOT WATER TEMPERATURES REQUIRED FOR AUTOMATIC DISHWASHER AND LAUNDRY USE CAN CAUSE SCALD BURNS RESULTING IN SERIOUS PERSONAL INJURY AND/ OR DEATH. THE TEMPERATURE AT WHICH INJURY OCCURS VARIES WITH THE PERSON'S AGE AND TIME OF EXPOSURE. THE SLOWER RESPONSE TIME OF CHILDREN, AGED OR DISABLED PERSONS INCREASES THE HAZARDS TO THEM. NEVER ALLOW SMALL CHILDREN TO USE A HOT WATER TAP, OR TO DRAW THEIR OWN BATH WATER. NEVER LEAVE A CHILD OR DISABLED PERSON UNATTENDED IN A BATHTUB OR SHOWER.
THE WATER HEATER SHOULD BE LOCATED IN AN AREA WHERE THE GENERAL PUBLIC DOES NOT HAVE ACCESS TO SET TEMPERATURES.
It is recommended that lower water temperatures be used to avoid the risk of scalding. It is further recommended, in all cases, that the water temperature be set for the lowest temperature which satisfies the user's hot water needs. This will also provide the most energy efficient operation of the water heater and minimize scale formation.
SETTING THE WATER HEATER TEMPERATURE AT 120°F WILL REDUCE THE RISK OF SCALDS. Some states require settings at specific lower temperatures. Table 1 below shows the approximate
Table 1: Risk of Scalds
Time to Produce 2nd & 3rd
Degree Burns on Adult Skin
About 1/2 second
Less than 5 seconds
About 30 seconds
120°F or less
More than 5 minutes
Water heater life depends upon water quality, water pressure and the environment in which the water heater is installed. Water heaters are sometimes installed in locations where leakage may result in property damage, even with the use of a drain pan piped to a drain. However, unanticipated damage can be reduced or prevented by a leak detector or water shutoff device used in conjunction with a piped drain pan. These devices are available from some plumbing supply wholesalers and retailers, and detect and react to leakage in various ways:
•Sensors mounted in the drain pan that trigger an alarm or turn off the incoming water to the water heater when leakage is detected.
•Sensors mounted in the drain pan that turn off the water supply to the entire home when water is detected in the drain pan.
•Water supply shutoff devices that activate based on the water pressure differential between the cold water and hot water pipes connected to the water heater.
•Devices that will turn off the gas supply to a gas water heater while at the same time shutting off its water supply.
The Boiler is equipped with a blocked vent
DO NOT ATTEMPT TO OPERATE THE BOILER if this situation occurs. Shut the boiler off before performing all the steps shown in "TO TURN OFF GAS TO APPLIANCE" section of the Lighting and Operating Instructions.
Contact a qualified service agent to inspect the unit and vent system and correct the problem.
The flue products are corrosive in nature and if the boiler is vented horizontally the flue gases are at a higher pressure than
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 flue products. Call a qualified service agent to replace or repair any corroded or leaking parts.
A qualified service agent must inspect the internal surfaces of the vent system and the boiler at least once a year.
To maintain safe operation and the greatest efficiency for the boiler, observe the burner flame through the observation port on the jacket panel, once a month for proper flame characteristics.
•The burners should display the following characteristics:
•Provide complete combustion of gas.
•Cause rapid ignition and carry over across all burners and across the entire burner.
•Give quiet operation during ignition, burning and extinction.
•Cause no excessive lifting of flames from the burner ports.
If the preceding characteristics are not evident, check for accumulation of lint or other foreign material that restricts the inlet air or burner ports. Ensure there is the proper amount of air to the burner. Flame lifting from the burner is caused by too much air to the burner.
The burners must be inspected by a qualified service technician at least once a year.
DO NOT STORE COMBUSTIBLE MATERIALS, GASOLINE, OR OTHER FLAMMABLE VAPORS, LIQUIDS IN THE AREA OF THE APPLIANCE. NONCOMPLIANCE MAY RESULT IN FIRE OR EXPLOSION. DO NOT OBSTRUCT THE FLOW OF COMBUSTION OR VENTILATION AIR TO THE APPLIANCE.
CHEMICAL VAPOR CORROSION
Boiler corrosion and component failure can be caused by airborne chemical vapors. Spray can propellants, cleaning solvents, refrigerants, calcium or sodium chloride (water softener salts), waxes, and process chemicals are typical compounds that are potentially corrosive. These materials are corrosive at very low concentration levels with little or no odor to reveal their presence. Products of this sort should not be stored near the boiler. Air which is brought in contact with the boiler should not contain any of these chemicals. The boiler should be provided with air from outdoors when installed in environments having corrosive atmospheres.
Refer to the pump manufacturer's schedule of maintenance for frequency and method of lubricating the pump and motor. Inspect the pump once a month for leaky mechanical seals and/or
ELECTRONIC HOT SURFACE
IGNITION CONTROL BOARD
The EMC5000 control system is a fully integrated, state of the art electronic control system. It consists of sensors, output devices, a power switch, a 24vac transformer, wiring, and the following printed circuit boards:
Central Control Board (CCB).
See Figure 1A.
Flame Control Board (FCB).
See Figure 1B.
User Interface Board (UIB).
This part of the User Interface
Module (UIM). See Figure 3.
Power Distribution Board (PDB). See Figure 1C.
Touch Sensor Board (TSB).
This is part of the User
Interface Module (UIM). See
The CCB contains circuitry for both master control and flame control for the first stage. The FCB contains circuitry for flame control on up to one additional stage. Dip switches on the CCB and FCB are used to configure the system. The UIB and TSB are included in the User Interface Module (UIM) along with a 4 line by
Dual stage control is accomplished by means of an internal communication network and the FCB's. One FCB is required for each stage beyond initial first stage. The CCB also contains an external communications system to allow for connection to a PC, a modem, or an EMS system. Through this connection multiple boilers can also be linked together.
The internal communications cables should never be connected to the external communications connectors and
There are several microcontrollers used on the board. Three on the CCB, two on the FCB, and one on the UIB. These micros control the temperature and ignition control functions for the boiler. Inherent in the design are the normal operating sequences and safety features associated with a gas ignition control system. The system continuously performs various diagnostic tests to verify proper appliance and control operation. Should an unsafe condition occur, the control will shut down the burner and display a red fault light as well as indicate the cause of the fault on the display. The operating programs for the system are stored in permanent memory inside the micros.
Inputs To CCB and FCB:
•Temperature probes (CCB - outlet and either inlet or tank is required): The CCB accepts analog temperature inputs from up to three sensors (inlet, outlet and tank).
•ECO input (CCB - required):
The ECO (Energy
•Thermostat input (CCB - optional):
This input is set up to work with an externally connected thermostat that provides a contact closure. If this input is
Figure 1A. CCB (Drawing #211758)
Figure 1B. FCB (Drawing #211759)
Figure 1C. PDB (Drawing #211760)
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 the thermostat is controlling to. This will allow the thermostat to control the boiler. When the thermostat closes, a call for heat will be generated until the thermostat determines that the control temperature has been reached.
•Air Pressure Sensors (open condition indicates fault):
•Blocked Flue (CCB - required)
•Normally closed switch that opens if the flue becomes blocked during operation.
•Powered Vent (CCB - optional):
Normally open switch that closes when the powered vent is operating properly. This input is
•Blower Prover High (FCB - required on stages that have blowers):
Normally open switch that closes when the air pressures produced by the
•Gas Pressure Sensors (open condition indicates fault):
•Low Gas (CCB - optional):
Normally open switch that closes when the gas pressure rises above the trip level. This input is enabled/disabled by a dipswitch on the CCB.
•Hi Gas (FCB - optional):
Normally closed switch that opens in the gas pressure exceeds a set value. This input is enabled/disabled by a dipswitch on the CCB and FCB's.
•Water Level Sensor (open conditions indicates fault):
•Low Water Cut Off (CCB - optional):
Normally closed switch opens if a low water condition occurs. This input is enabled/disabled by a dipswitch on the CCB.
•Water Flow Sensor:
•Flow (CCB - required):
Normally open switch that closes when flow exceeds a set value.
•IRI Gas Valve Sensor:
•IRI Gas Valve (CCB - optional):
Normally open switch that closes when the IRI Gas Valve is operating correctly. This input is enabled/disabled by a dipswitch on the CCB.
•Flame (FCB - required on stage 1 and on stage 2 of a 4 stage system - optional on others):
Returns a signal to the microprocessor if flame is detected in the burner. This input is enabled/disabled by a dipswitch on the FCB.
Outputs from CCB and FCB's :
•Relay Contact Outputs:
•IRI Gas Valve (CCB - 120vacoptional):
Provides electrical power to operate an IRI Gas Valve device.
•Alarm (CCB - 24vacoptional):
Provides electrical power to operate on external alarm. This can be an audio device (i.e. Sonalert), a visual device (lamp), or any other device that will operate with the voltage and current level provided.
•Pump (CCB - 120vac - required on systems that do not have an external pump):
Provides electrical power to directly operate a pump or the coil of an externally connected contactor.
•Powered Vent (CCB - 24vac - optional):
Provides electrical power to operate a powered vent.
•Low and High Speed Blowers (FCB - 120vac - required on
stage 1 and on stage 2 of a
Independent outputs that provide power to operate low and high speed blower output. Dip switches on the FCB's enable/ disable the use of blowers on stages 2, 3 and 4.
•Igniter (FCB - 120vac - required on stage 1 and on stage 2 of a
Provides power to operate the Silicon Carbide igniter. Dip switches on the FCB's enables/disables the use of an igniter on stages 2, 3 and 4.
•Gas Valve (FCB - 24vac - required):
Provides power to activate the gas valve. The gas valve cannot be activated when the ECO contacts are open.
•Direct Connection Output:
•Low Water Cut Off (CCB - 24vac - optional):
Directly connected to the 24 vac line to provide power to operate an external LWCO device.
Line Polarity Indicator & Fuse Protection
CCB/FCB Indicator Lamps & Fuses
A green LED is mounted on the PDB to indicate when line voltage is applied. (The PDB also contains a yellow LED, a red LED, and a
Repeated failure of fuse is an indication of failure to some part of the system.
Yellow LED's are located near the micros on the CCB and FCB's. These LED's are "heartbeat indicators" and blink approximately twice per second to indicate that the micros are running.
The Genesis 400 Series Boilers use a Silicon Carbide Igniter.
Appliance Operating Sequence
NOTE: The following sequence is based on a
1.The EMC5000 controller has four modes of operation: Initialization, Standby, Running and Service. The internal CCB and FCB micros control these modes through a sequence of steps (or States) which are further described in the "UIM Operating Procedures" section.
2.When power is applied to the system, it enters the Initialization mode and the following automatic functions are performed:
•A. O. Smith opening screen is displayed on the UIM.
•The system goes through a
CCB/FCB Dip Switches:
Dipswitch configurations are READ ONLY ON POWER UP. These switches are only to be set at the factory or by authorized trained personnel only! Once set at installation they generally remain that way for the duration of the life of the product. If a switch is changed, power must be cycled before the change will take effect. The status of all dipswitches can be observed on the system status screen on the UIM.CCB - Ten Position Dipswitch (Central Control Section):
Switch 1: Selection of the type of boiler application:
Switch 2: Trials for ignition:
Switch 3: IRI Gas Valve Option:
On = IRI
= No IRI
Switch 4: Controlling Probe:
On = Tank
Off = Inlet
Switch 5: Powered Vent:
On = Yes
Off = No
Switch 6: Low Water Cut Off:
On = Yes
Off = No
Switch 7: Low Gas
On = Yes
Off = No
Switch 8: Spare:
Switch 9 & 10. Number stages (FCB's):
NOTE: If the unit power up with the number of stages selected by dip switches exceeding the number of FCBs, the CCB will detect this condition and go into a hard lockout. After changing the dip switches to the correct number of stages, the power must be cycled off and on to accept the change.
Example of Dip Switch configuration:
GW model, 1 ignition trial, No IRI, Inlet control, No Power Vent, No LWCO,
No Low Gas, 2 stage.
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, igniter, flame checking, and the address is always stage 1.
FCB - Eight position Dipswitch:
Switch 1: Spare:
Switch 2: Hi Gas:
Switch 3: Number of Blower Speeds:
Switch 4: Igniter used:
Switch 5*: Blower used:
Switch 6: Flame Checked:
Switch 7 & 8. Stage selection:
*When switch 5 is in off (no blower) position, switch 3 (blower speeds) is ignored.
Example of Dip Switch configuration:
No High Gas, 1 blower speed, no igniter, no blower, flame not checked, Stage 2.
•Stored values are recalled from memory.
•Configuration dipswitches are read.
•Pending faults are recalled
•Micros on all boards start running (indicated by a flashing Yellow LED near each micro)
•Input sensors are read
•Communications between micros and boards is established
•FCB's are configurated with the number of ignition trials to run.
3.After initialization is complete (approximately 10 seconds) the system turns the green LED off and goes to the standby mode (yellow "Standby" LED on), unless a previously stored fault has been recalled, which will send the system into the service model (red "Service" LED on). In standby mode the display shows the temperature screen and in fault mode the current error screen is displayed.
4.The system then compares the temperature read from the controlling probe (inlet or tank) to the setpoint temperature. If 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 shifts to the run mode (green "Running" LED turns on).
5.The heating sequence begins by applying power to the pump and, if selected, the powered vent and the IRI gas valve.
6.After a few seconds the High Speed Blower (on all stages with the blower dipswitch turned on) are turned on to perform a cold purge of the chamber.
7.After cold purging is complete the blowers are turned off and the stage 1 blower is turned on.
8.The stage 1 igniter is turned on.
9.After 18 seconds the system checks that the igniter has turned on. If this is ok then the system turns on the gas valve.
10.After 1.5 seconds the system checks the status of the flame sensor. Note: If the "Ignition Tries" dipswitch is set for 3 tries the system will not declare an error until it tries the ignition sequence three times. If it is set to 1 try then the system will declare an error anytime a fault is detected.
11.The system now activates the other FCB stages depending upon a control algorithm scheme that is described below. For this example it is assumed that all four stages of heat are required.
12.The stage 2 blower is turned on to purge the chamber.
13.After approximately 10 seconds the stage 2 igniter is turned on.
14.After 18 seconds the system checks that the igniter has turned on. If this is ok then the system turns on the gas valve.
15.After 1.5 seconds the system checks the status of the flame sensor.
16.Steps 12 through 15 are then repeated for stage 3 and 4.
17.The system is now in the heating mode with all four stages on and will remain in this mode until the call for heat is satisfied or a fault occurs.
NOTE: In standby and running modes the system constantly monitors the signals and the internal operation for faults. Any detected fault will halt the heating sequence and shift the system to the service mode, where the detected fault will be displayed.
Temperature Setpoints (System Control Algorithm)
The boiler has a hysteresis type control, which means that it will begin heating the water when the temperature sensed by the
control probe (inlet or tank) falls below the operating setpoint minus the differential setpoint for stage 1. It will stop heating the water when the temperature rises to the operating setpoint. If the system has multiple stages then the differential setpoint for each stage is also subtracted from the operating setpoint. The following examples will further explain this operation.
Setup: 2 stage system, operating setpoint - 140, stage 1 to 2 differential setpoints = 10.
Example 1. Temperature begins at 150 and drops to 90, see Figure 2A. At 140 the system remains in idle mode. As the temperature drops to 130
Example 2. Temperature begins at 90 and rises to 150, see Figure 2B). At 100 both stages are on. (This is the case when a boiler is first started and the controlling temperature is below the operating setpoint minus all of the differential setpoints. At that time both stages are turned on, in sequence from 1 to 2. At 130 stage 2 turns off. At 140 both stages are off.
Example 3. Boiler is initially started and the controlling temperature is at 95, see Figure 2B). Both stages will turn on in sequence from stage 1 to stage 2.
Example 4. Boiler is initially started and the controlling temperature is at 125, see Figure 2B).
Stages 1 and 2 will turn on in sequence from 1 to 2.
UIM Operating Procedures
FIGURE 3. UIM
The UIM receives commands from the user and displays operational information to the user via an LCD (liquid crystal display) up to eleven LED's, and five touch switches. The LCD provides information to the user by the use of 10