Specifications

45
LP- 276 REV. 9.4.14
use of a pipe sensor will be somewhat less accurate
than using a sensor in the tank, and has the
disadvantage of requiring the boiler pump(s) to run
continuously so the sensor is always measuring the
tank water temperature.
In a multiple Mod Con 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 system sensor is mounted on
the common pipe to 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 and
provide it with the aggregate temperature of all firing
boilers. The master boiler control will then fire the
boilers in cascade sequence to maintain the water
temperature in this pipe and provide correct tank
heating.
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 standard CAT3 or CAT5
patch cables.
D. LINE VOLTAGE WIRING
NOTE: A termination plug is included in the CAT 3 /
CAT 5 Bus Connection Point, labeled J3 in Figure 24.
DO NOT REMOVE THIS PLUG! Doing so will affect
boiler operation and void warranty.
Connect the incoming power wiring to the line voltage
terminal strip in the electrical junction box at terminals
LINE 120V, Neutral, and Ground (shown in Figure 24).
A line voltage fused disconnect switch may be required
to be externally mounted and connected according to
local wiring codes.
If the pump used for the boiler operates at 120 volts
and less than 3 amps is required, it may be connected
directly to the terminals marked BOILER HOT, BOILER
NEUT, and BOILER GRD. If the pump operates at a
voltage other than 120 volts and/or 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 Figure 24 for a representative
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 followed.
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 normal operation and the circuit between ALARM COM and NO is open
during normal operation. The connections depicted in Figure 24 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 turn on when the boiler is in lockout mode.
Figure 24 - Mod Con VWH Control