Heat Demands; Spare Inputs; Inputs, Bms; Outputs, Pump - Bradford White OmniTech BONH1250 Installation And Operation Instructions Manual

Page 38
7.E.6

Heat Demands

(Boiler / Water Heater)
CH1/DHW1 - if a thermostat/aquastat or end switch
(isolated contact only) is used as a heat demand, connect
to terminals 37 and 38 . CH1/DHW1 functionality is
configured on the touch screen on the CH1/DHW1
screens.
CH2/DHW2 – if an additional thermostat/aquastat or
end switch (isolated contact only) is required as a heat
demand, connect to terminals 39 and 40. CH2/DHW2
functionality is configured on the touch screen on
CH2/DHW2 screens.
DHW/DHW3 – if an aquastat, end switch (isolated
contact only), or flow switch is used as a DHW heat
demand, connect to terminals 41 and 42. If preferred, a
DHW tank sensor can be used in lieu of an aquastat to
generate a heat demand (see Sensors section above).
NOTE: CH1/DHW1, CH2/DHW2, and DHW heat demand
contacts must be dry contacts. The controllers heat
demand voltage is 24VDC.
7.E.7

Spare Inputs

There is no functionality associated with these inputs.
7.E.8 Analog Input, BMS
BMS – if an analog input (0-10VDC or 4-20mA) from a
Building Management System is used as a remote set
point or remote firing rate command, wire to terminals
47 and 48 (See Figure 13 on page 36). Polarity is
shown on the terminal label. Selecting voltage or current
input is accomplished through jumper placement on the
control board. See Figure 14. Analog BMS functionality
is configured using the touch screen.
7.E.9 Analog Output, Pump
Pump – when using Vari-Prime pump control, wire the
pump speed wires to terminals 49 and 50. Polarity is
shown on the terminal label. Selecting voltage or current
output is accomplished through jumper placement on the
control board. See Figure 14. Vari-Prime functionality is
configured using the touch screen.
7.E.10 Dry Contacts (Run & Alarm)
Run - when used, is connected to terminals 51
(common), 52 (normally closed), and 53 (normally open)
(See Figure 13 on page 36). The controller closes
the normally open set of contacts whenever the unit is
running. Contact ratings are 250VAC, 0.6A maximum.
Alarm - when used, is connected to terminals 54
(common), 55 (normally closed), and 56 (normally
open). The controller closes the normally open set
of contacts whenever the unit is locked out. Contact
ratings are 250VAC, 0.6A maximum.
7.E.11 RS485 for Cascade (Lead Lag)
This commercial unit can be connected in Lead Lag
up to a total of 8 units (controllers). One as the Lead
control and up to 7 more as the Lag controllers.
Prior to wiring units for cascade operations, select one
unit as the lead boiler/heater. Other units connected
to the lead boiler/heater will be referred to as lag
units. Communication between lead and lag units is
accomplished using RS485. When wiring these units
for cascade operations, use terminals 57, 58, and 59
(See Figure 13 on page 36). Use 2-wire twisted
pair, shielded w/drain (communication cable) between
units. Connect one wire of the communication cable to
A (-), terminal 58, and the other wire to terminal B (+),
terminal 57, and a third conductor to GND, terminal 59
(see RS485 NOTE: Grounding). Connect the other end
of the cable to the next unit, matching the termination
wiring on the previous unit. If more than two units are
cascaded together, daisy chain the wiring from unit to
unit, keeping the cables as short as possible. A system
supply sensor must be installed and connected to the
lead boiler. The lead boiler will use this system supply
sensor as the temperature control sensor for cascade
operations.
Section 8.D.4.a on page 75 shows how these systems
are configured in the touchscreen controls. Any heat
demand at the lead boiler/heater will be treated as a
cascade heat demand.
When servicing the controls, label all wires prior to
disconnection. Wiring errors can cause improper and
dangerous operation. Verify proper operation after
servicing.
WARNING