Water Heater User Manual

1 Service (continued)
23
0 - 10Vdc BMS Parameters Screen:
0-10Vdc Operation
When the Demand Configuration parameter (see page 18)
is set to either Cascade BMS Thermostat Based, Cascade
BMS Voltage Based, Cascade Modbus BMS Thermostat
Based, or Cascade Modbus BMS Voltage Based; a 0 - 10Vdc
signal can be supplied to the terminal strip connection or
through Modbus communications to control a single unit or
a multiple unit cascade.
The BMS Screen allows access to 12 parameters. Those
parameters are:
• BMS Type - When the unit or cascade is controlled by the
0-10Vdc BMS input, the voltage signal can control either
the modulation rate or set point. This parameter can only
be changed by the installer. The default method of
control is modulation rate.
• ModBus Time - When the tank temperature reading is
provided through the ModBus control, it should be
refreshed on a regular basis. This setting defines the
maximum time it must be refreshed. If the time expires,
the control will revert to its local reading.
• BMS Set Point at Minimum Voltage - Determines the set
point used by the unit or cascade when the BMS voltage
is at or below the setting of the BMS Voltage Minimum
Set Point parameter. This parameter is only active when
the BMS Type is set to Set Point. This parameter can only
be changed by the installer. The temperature range of this
parameter is 32° to 179°F. The default value is 70°F.
• BMS Set Point at Maximum Voltage - Determines the set
point used by the unit or cascade when the BMS voltage
is at or above the setting of the BMS Voltage Maximum
Set Point parameter. This parameter is only active when
the BMS Type is set to Set Point. This parameter can only
be changed by the installer. The temperature range of this
parameter is 70° to 190°F. The default value is 179°F.
• BMS Voltage at Minimum Set Point - Determines the
voltage at which the external signal begins to increase the
set point. Below this voltage, the set point will be at the
setting of the BMS Set Point Minimum Voltage
parameter. This parameter is only active when the BMS
Type is set to Set Point. This parameter can only be
changed by the installer. The range of this parameter is 0
to 10V. The default value is 2V.
• BMS Voltage at Maximum Set Point - Determines the
voltage at which the external signal forces the set point to
the setting of the BMS Set Point Maximum Voltage
parameter. This parameter is only active when the BMS
Type is set to Set Point. This parameter can only be changed
by the installer. The range of this parameter is 2V to 10V.
The default value is 10V.
• BMS Voltage at Start Call for Heat - When the Demand
Configuration parameter (see page 18) is set to Cascade
BMS Voltage Based, this parameter determines the BMS
input voltage at which the unit or cascade is enabled. The
unit or cascade will become enabled when the BMS input
voltage rises up to or above this value. This parameter can
only be changed by the installer. The range of this
parameter is 0 to 10V. The default value is 2V.
• Drop in BMS Voltage to End Call for Heat - When the
Demand Configuration parameter (see page 18) is set to
Cascade BMS Voltage Based, this parameter determines the
BMS input voltage at which the unit or cascade is disabled.
The unit or cascade will become disabled when the BMS
input voltage drops down to or below the BMS voltage at
start call for heat minus this value. This parameter can only
be changed by the installer. The range of this parameter is
0 to 10V. The default value is 1V.
Service Manual