Field Wiring - A.O. Smith VB/VW 1500, 2000 Instruction Manual

Z223.1/NFPA 54 or the Natural Gas and Propane Installation
Code, CAN/CSA B149.1
• Table 7 is based on a pressure drop of 0.5 inches water column
(0.124kPa), and a gas with a specific gravity of 0.60 and a heating
value of 1,000 BTU/ft , approximately that of Natural Gas.
3
• Table 8 is based on a pressure drop of 0.5 inches water column
(0.124kPa), and a gas with a specific gravity of 1.53 and a heating
value of 2,500 BTU/ft3, approximately that of Propane Gas.
No additional allowance is necessary for an ordinary number of fittings.
Where it is necessary to use more than the average number of fittings
(i.e., elbows, tees and valves in gas supply line) use a pipe larger than
specified to compensate for increased pressure drop.
SINGLE UNIT INSTALLATION, SUGGESTED GAS PIPE SIZING.
MAXIMUM EQUIVALENT PIPE LENGTH (IN FEET).
1-1/4"
BTU
Input
Nat Pro Nat
1,500,000 ----- ----- 10
2,000,000 ----- ----- -----
Natural gas 1000 Btu/ft^ , 0.60 specific gravity
3
Propane gas 2500 Btu/ft^ , 1.50 specific gravity
3
Table 6 shows the maximum equivalent gas pipe length for a single
unit installation. It does not take into account other appliances that
may be connected to the gas line. For installation of multiple units,
or instances where several appliances are connected to the same
line, use Tables 7 and 8 for proper sizing.

FIELD WIRING

Label all wires prior to disconnection when servicing controls.
Wiring errors can cause improper and dangerous operation. Strict
adherence to the wiring diagrams is required to ensure proper
operation. Verify proper operation after servicing; allow the boiler
to complete at least one full heating cycle. If any of the original
wire, as supplied with the appliance, must be replaced, it must be
replaced with type 105°C wire or its equivalent.
120 VAC POWER SUPPLY WIRING
A dedicated, single phase, 30 amp circuit breaker with a grounded
neutral should be provided to supply power to the boiler. Use #10
AWG wire for the 120 VAC power supply to the boiler. All 120 VAC
power supply connections must be made as shown in Figure 12D.
These connections should be made at the rear of the unit where a
wiring junction box is provided. Field installed power supply wiring
to the boiler should be installed in conduit. This conduit and wiring
should be separate from any other conduit/wiring to guard against
EMI (electromagnetic interference).
POWER SUPPLY CHECK
To reduce the possibility of electrical interference with the boiler's
control system the power supply voltage, polarity and ground
must be checked. Using an AC volt meter check the 120 VAC
power supply wiring from the breaker prior to making power supply
connections at the boiler. Confirm the power supply voltage &
polarity are correct and that an adequate ground connection is
TABLE 6.
1-1/2" 2"
Pro Nat Pro Nat
30 60 80 125
----- 30 60 70
@ 0.3 in. w.c. pressure drop.
@ 0.3 in. w.c. pressure drop.
present by performing the three voltage tests below. Refer to Figure
12D for these tests.
Confirm RMS voltage between:
• H and GND = 108 VAC minimum, 132 VAC maximum.
• N and H = 108 VAC minimum, 132 VAC maximum.
• N and GND = < 1 VAC maximum.
POWER SUPPLY AND SYSTEM CONTROL - FIELD WIRING
H - 120 VAC HOT
120 VAC
INPUT
N - 120 VAC NEUTRAL
POWER
GND - EARTH GROUND
SUPPLY
FACTORY SUPPLIED REMOTE
TEMPERATURE PROBE OR QUAD
2-1/2"
THERMISTOR PROBE
Pro
-----
FIELD SUPPLIED
100
EXTERNAL CONTROL
COM
NO
LOW VOLTAGE CONTROL WIRING
There are four low voltage control wires in the junction box on the
back of the boiler; two yellow wires, one black/white stripe wire
and one yellow/violet stripe wire, see Figure 12D. These wires are
provided to connect factory supplied Remote Temperature Probes
and field supplied external controls to the boiler control system's
Enable/Disable circuit.
All low voltage control wiring connections must be made as shown
in Figure 12D. These connections should be made at the rear of
the unit where a wiring junction box is provided. Field installed
wiring inside 1/2 inch conduit is installed between the junction box
on the back of the boiler and the temperature probe and/or field
supplied external control being used. This conduit and wiring should
be separate from any other conduit/wiring to guard against EMI
(electromagnetic interference).
TEMPERATURE PROBE WIRING
The two yellow wires in the boiler's junction box are to be
used with the supplied Remote Temperature Probe or one of
the four temperature sensor circuits from an optional Quad
Thermistor Probe only. This is a temperature probe circuit
only; DO NOT apply any external voltage or connect any load
(IE: relay coil) to this circuit wiring under any circumstances.
DO NOT short/connect these two wires together under any
circumstances. See the Primary System Control and the
Remote Temperature Probe Installation sections of this manual
for operating and installation instructions.
ENABLE/DISABLE CIRCUIT WIRING
The black/white stripe and the yellow/violet stripe wires in the
boiler's junction box are the control system's Enable/Disable
circuit. The Enable/Disable circuit may be used with field supplied
external controls. The Enable/Disable circuit is a switching circuit
only; DO NOT apply any external voltage or connect any load
(IE: relay coil) to this circuit wiring under any circumstances.
The Enable/Disable circuit is always active. From the factory
the two Enable/Disable circuit wires are joined together with
a wire nut to "enable" boiler operation. If this circuit will not
be used these two wires must remain connected together to
enable boiler operation. See the Primary System Control and
the Field Supplied External Control Installation sections of this
manual for operating and installation instructions.
26
FACTORY INSTALLED WIRING
JUNCTION BOX
BACK OF BOILER
FIELD INSTALLED WIRING
HIGH VOLTAGE
WIRING
BLACK - 120 VAC HOT
WHITE - 120 VAC NEUTRAL
GREEN - GROUND
LOW VOLTAGE
CONTROL WIRING
YELLOW - 5 VDC
YELLOW - 5 VDC
BLACK/WHITE STRIPE - 24 VAC
YELLOW/VIOLET STRIPE - 24 VAC
FIGURE 12D.
REMOTE
TEMP
PROBE
ENABLE
DISABLE
CIRCUIT