Wiring - A.O. Smith HW 300 Installation & Operation Manual

Adjustment, if required, is performed as follows:
1. Set primary system temperature control dial (thermostat) at
lowest setting so that boiler will not call for heat.
2. Attach a pressure gauge to the tapping in the control string
elbow.
3. Reset primary system temperature control dial (thermostat) to
highest setting. Main burner will now ignite.
4. With main burner firing, adjust pressure, if necessary, by turning
pressure regulator adjusting screw with a screwdriver.
• Clockwise to increase pressure.
• Counterclockwise to decrease pressure.
WIRING CONNECTIONS
LABEL ALL WIRES PRIOR TO DISCONNECTION WHEN
SERVICING CONTROLS. WIRING ERRORS CAN CAUSE
IMPROPER AND DANGEROUS OPERATION. VERIFY PROPER
OPERATION AFTER SERVICING.
1. CONVENTIONAL INSTALLATIONS
ALL ELECTRICAL WORK MUST BE INSTALLED IN ACCORDANCE
WITH NATIONAL ELECTRICAL CODE, ANSI/NFPA 70 AND/
OR THE CANADIAN ELECTRICAL CODE, PART 1, CSA C22.1,
ELECTRICAL CODE AND MUST CONFORM TO LOCAL
REGULATIONS.
The boiler, when installed, must be electrically bonded to ground in
accordance with the requirements of the authority having jurisdiction
or, in the absence of such requirements, with the National Electrical
Code, ANSI/NFPA 70 and/or the Canadian Electrical Code Part 1,
CSA C22.1, Electrical Code.
STRICT ADHERENCE TO PIPING AND WIRING DIAGRAMS IS
REQUIRED TO PREVENT CONSTANT PUMP OPERATION WHEN
SYSTEM TEMPERATURE CONTROL IS SATISFIED. OTHERWISE
THE WARRANTY IS VOID AS STIPULATED IN THE LIMITED
WARRANTY ON THE INSTRUCTIONS MANUAL.
CAUTION
5. Set primary system temperature control dial (thermostat) to
lowest setting.
6. Remove pressure gauge and replace sealing plug.
7. Set primary system temperature control dial (thermostat) to
desired setting.
DO NOT INCREASE GAS PRESSURE ABOVE THAT SPECIFIED
ON THE RATING PLATE, AS OVERFIRING WILL RESULT IN
DAMAGE TO THE BOILER, AS WELL AS INCREASED RISK
OF FIRE, SOOTING AND ASPHYXIATION.
If gas pressure regulator cannot be adjusted to correct pressure with
sufficient gas pressure at the valve, replace with new gas valve.

WIRING

The electrical connections must be made so that the circulator will
operate before the gas valve opens. At no time may the controlling
system allow the burner to fire when there is no water flow through
the boilers.
Refer to the diagrams in Figures 16 and 17 on pages 24 and
25 for proper wiring sequence with conventional single boiler
installations.
The THERMAL BALANCER shown is factory included by
A. O. Smith. This device serves as a pump shutdown delay switch to
balance the rising boiler water temperature to system temperature
before the pump stops. Overshooting of boiler temperature is
prevented and stack loss after shutdown is negligible.
AN ELECTRICAL GROUND IS REQUIRED TO REDUCE RISK OF
ELECTRIC SHOCK OR POSSIBLE ELECTROCUTION. Make the
ground connection to the screw provided in the electrical supply
junction box on the boiler.
IF ANY OF THE ORIGINAL WIRE, AS SUPPLIED WITH THE
APPLIANCE, MUST BE REPLACED, IT MUST BE REPLACED
WITH TYPE 105
0
THE FLAME SENSOR AND IGNITION CABLE WHICH ARE 250
AND WIRES CONNECTED TO THE COIL PROTECTOR WHICH
ARE 200 C.
0
23
WARNING
WARNING
C WIRE OR ITS EQUIVALENT, EXCEPT FOR
C
0