Boiler Management System - Watts AERCO KC Series User Manual

5. Follow the above directions to change back
to remote mode.
NOTE:
The unit automatically defaults to remote
mode upon AC power being applied. This is
due to the presence of the external interface
board.
5.4 4 to 20MA DIRECT DRIVE MODE
In this mode of operation the 4 to 20ma signal
sent to the unit changes the unit's percentage of
firing rate. The signal is typically sent from an
energy management system that, through PID
controls, determines the rate of change
necessary in the supply header. The 4 to 20ma
signal sent from the energy management
system equals a firing rate between 0 to 100%.
In this mode 4ma equals 0% firing rate and
20ma equals 100% firing rate. The unit is a
slave to the energy management system and
does not have a role in temperature control. This
mode of operation can be used to drive single as
well as multiple units.
In this mode, the external interface board is
utilized. The interface board, located in the
external field wiring box, is factory configured
and converts the 4 to 20ma signal to an RS-485
signal. The RS-485 signal is in turn sent to the
temperature controller. For the temperature
controller to recognize a signal, from an external
source, the following functions must be correctly
set.
MENU FUNCTION
Secondary Lore
Secondary FUNC
Primary Auto
5.4.1 4 to 20MA DIRECT DRIVE FIELD
WIRING
The only wiring necessary is the 4 to 20 ma
signal from the source, to terminals 13 and 14 in
the external field wiring box. The signal must be
floating, (ungrounded), and the wire used must
be a two wire shielded cable of 22 gauge
minimum. Polarity must be observed and the
shield must be connected to terminal 1 in the
external wiring relay box. The source end of the
end must be left floating and not connected.
When driving multiple units, each unit's wiring
must conform to the above.
5.4.2 4 to 20 MA DIRECT DRIVE
STARTUP
Since this mode of operation is factory preset
and the percentage of firing rate is being
externally controlled there are no startup
instructions necessary. However the unit must
be taken out of remote mode, and set to local
mode, to manually run the unit. Once finished
with manual mode, it is necessary to set the unit
back to remote mode for it to accept signals
from an external source. The temperature
controller must also be left in manual and not
automatic mode.
To set the unit to local mode do the following:
1. Access the temperature controller's
2. Scroll through the menu until "lore" is
3. Use the
4. Press ENTER to accept the change.
5. Follow the above directions to change back
The unit automatically defaults to remote
mode upon AC power being applied. This is
due to the presence of the external interface
SETTING
re

5.5 BOILER MANAGEMENT SYSTEM

Cont
(BMS)
OFF
The BMS mode of operation is used when it is
desired to operate multiple units in the most
efficient manner possible. A total of eight units
can be managed by a single AERCO BMS 168
system. In BMS mode, the Boiler Management
System modulates the units firing rate. All
temperature functions are monitored and
controlled by the BMS panel. For BMS
programming and operation see the BMS
Operations Guide.
In BMS mode, the external interface board is
utilized. The interface board, located in the field
wiring box, is factory configured, and converts
the pulse width modulation signal, sent from the
BMS, to an RS-485 signal. The RS-485 signal is
then sent to the temperature controller. For the
temperature controller to recognize a signal,
26
MODE OF OPERATION
secondary menu.
displayed.
keys to set the temperature
controller to local. The yellow REM light, on
the temperature controller, should extinguish
to remote mode.
NOTE:
board.