Heat Transfer MODCON VWH 300 HL, Installation & Maintenance

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PART 8: FIELD WIRING
A. INSTALLATION MUST COMPLY WITH:
1. National Electrical Code and any other
national, state, provincial or local codes or
regulations.
2. In Canada, CSA C22.1 Canadian Electrical
Code Part 1, and any local codes.
B. FIELD WIRING TERMINATIONS
All connections to the MODCON VWH boiler in
the field are made inside the electrical junction
box located on the side of the unit. The electri-
cal junction box is located on the left side of the
MOD CON 500 and 850 and on the right side of
the MOD CON 300 units. Multiple knockout loca-
tions are available to route field wires into and
out of the electrical junction box.
C. FIELD WIRING CONSIDERATIONS
Pumps
The Mod/Con VWH Application requires a circu-
lator pump for each boiler. Circulator pumps can
be wired directly to the controller as shown fig-
ures 8-1/8-3/8-4 or wired directly to line voltage
for continuous operation. Only wire the circula-
tor pump to the controller if a Tank Sensor or
Mechanical control can be mounted to the stor-
age tank, otherwise circulator pumps must be
wired to run continuously. The circulator pump
wired to the boiler control will have a default
program of a 5 minute post purge to provide
stabilization and post cleaning of the heat
exchanger. The boiler control is capable of sup-
plying 120 volts at up to 3 amps to run the cir-
culator pump. If using a larger circulator pump
requiring more than 3 amps or higher voltage,
an external motor starter, sized appropriately for
the pump motor must be used. This starter
should have a 120 VAC coil. If a starter with 120
VAC coil is used, it can be wired directly to the
appropriate pump terminals as shown on fig-
ures 8-1 / 8-3/8-4 Mod/Con VWH.
Tank and Sensor Connections
When the MOD CON VWH is used in a single
boiler installation, it is recommended to use a
sensor (7250P-325) placed in a well in the stor-
age tank for the best temperature control. If mul-
tiple tanks are used in the installation, it is rec-
ommended to put a mechanical aquastat in each
tank and wire them in series to provide temper-
ature control of the tanks. See piping/sensor dia-
grams in Part 5 section G for reference. The con-
trol in the MODCON VWH will read either the
temperature of the tank sensor or the status of
the aquastats and cause the boiler to run until
the water temperature of the tank is at the
desired set point. If a sensor or aquastat cannot
be placed directly in the tank, then one sensor
should be used on the pipe carrying the water
from the tank(s) to the boiler. This sensor should
be placed as close to the tank(s) as possible in
the common piping to minimize loss of temper-
ature in the piping. The use of a pipe sensor will
be somewhat less accurate than using a sensor
in the tank and has the disadvantage of requir-
ing the boiler pump(s) to run continuously so
the sensor is always measuring the temperature
of the water that is in the tank.
In a multiple MODCON VWH installation, where
the boilers are connected for cascade operation,
a system sensor is needed in addition to the
tank or pipe sensor described above. The sys-
tem sensor is mounted on the common pipe to
n
WARNING
ELECTRICAL SHOCK HAZARD — For your
safety, turn off electrical power supply at service
entrance panel before making any electrical
connections to avoid possible electric shock
hazard. Failure to do so can cause severe
personal injury or death.
NOTICE
Wiring must be N.E.C. Class 1.
If original wiring as supplied with boiler must be
replaced, use only TEW 105 °C wire or
equivalent.
Boiler must be electrically grounded as required
by National Electrical Code ANSI/NFPA 70 —
latest edition.
NOTICE
CHECK WATER CHEMISTRY SECTION FOR
ACCEPTABLE LEVELS. IF ACCEPTABLE, PUMPS
M AY B E W I R E D D I R E C T LY T O P U M P
TERMINALS. IF LEVELS ARE TOO HIGH, YOU
MUST WIRE PUMPS TO LINE VOLTAGE TO RUN
CONTINUOUSLY TO PREVENT LIME BUILD UP.
GAS-FIRED HOT WATER SUPPLY BOILER
Boiler Manual
44