Heat Transfer MODCON VWH 300 HL, Installation & Maintenance

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GAS-FIRED HOT WATER SUPPLY BOILER
Boiler Manual
45
normal operation and the circuit between
ALARM COM and NO is open during normal
operation. The connections depicted in figure 8-
1 show two 120 volt lights connected to the
alarm terminals. One light will be on when the
boiler is in normal mode and the other light will
be on when the boiler is in lockout mode.
F. LOW VOLTAGE CONNECTIONS FOR
STANDARD BOILER
1. All low voltage cables should enter the
electrical junction box through the provided
knock out holes as shown below.
2. Connect all low voltage field devices to the
low voltage terminal strip located in the
electrical junction box (shown in Figure 8-1).
the tank(s) from the boilers as close to the
tank(s) as possible. The purpose of this sensor is
to serve as feedback to the control to provide it
with the aggregate temperature of all boilers fir-
ing. The master boiler control will then fire the
boilers in cascade sequence to maintain the
water in this pipe at the appropriate temperature
to provide correct heating of the tank.
The electrical junction box has separate, clearly
marked terminal strips for line voltage and low
voltage wiring. Special jacks are provided for
trouble-free cascade system wiring using stan-
dard CAT3 or CAT5 patch cables.
D. LINE VOLTAGE WIRING FOR
MODCON VWH
Connect the incoming power wiring to the line
voltage terminal strip in the electrical junction
box at terminals LINE 120V, Neutral, Ground
(Shown in Fig. 8-1). A line voltage fused discon-
nect switch may be required to be externally
mounted and connected according to local
wiring codes that may apply.
If the pump used for the boiler operates at 120
volt and less than 3 amps is required, it may be
connected directly to the terminals marked
BOILER HOT, BOILER NEUT, BOILER GRD. If the
pump operates at a voltage other than 120 volts
and/or it requires more than 3 amps, an external
motor starter must be used to operate the
pump. If the starter is equipped with a 120 volt
coil, the coil connections may be connected
directly to the terminals marked BOILER HOT
and BOILER NEUT. Refer to Fig 8-1a for a repre-
sentative drawing of this configuration. If a
motor starter is used, it should be selected,
installed and wired in compliance with all local
electrical codes and requirements. In the
absence of such codes or requirements, the
National Electrical Code (NFPA 70) should be fol-
lowed.
E. ALARM CONNECTIONS
The MOD CON control includes a dry contact
alarm output. This is an SPDT circuit, rated at 5
amps at 120 volts. This contact can be used to
activate an alarm light or bell or notify a building
management system if the boiler goes into a
lockout condition. The circuit between the
ALARM COM and NC terminals is closed during
PART 8: FIELD WIRING
(CONTINUED)