MODE OF OPERATION
5-3
5. Use the
⇑
⇓
arrow keys to change “Auto”
from ON to OFF. The red “MAN” LED should
now be lit, indicating that the unit is in
manual mode.
6. Follow the above directions to change the
temperature controller back to operate from
the remote source.
NOTE:
The temperature controller 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
control box, is factory configured and converts
the 4-20mA 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
SETTING
Secondary
Lore
re
Secondary
FUNC
Cont
Primary
Auto
OFF
5.4.1 4-20mA DIRECT DRIVE FIELD
WIRING
The only wiring necessary is the 4-20mA signal
from the source to control wiring terminals 11
and 12 at the control box. The signal must be
floating, (ungrounded), and the wire used must
be a two wire shielded cable of 18 to 22 AWG.
Polarity must be observed and the shield must
be connected to terminal 1 at the control wiring
terminals. 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.
To run the unit in manual
mode, the temperature
controller must be
taken out of REMOTE mode and set to
LOCAL mode.
To set the unit to Manual mode do the following:
1. Access the temperature controller’s
secondary menu.
2. Scroll through the menu until "lore" is
displayed.
3. Use the
⇑
and
⇓
arrow keys to set the
temperature controller to local. The yellow
REM light, on the temperature controller,
should extinguish
4. Press ENTER to accept the change.
5. The unit is now in manual mode.
6. Follow the above directions to change the
temperature controller back to operate from
the remote source.
NOTE:
The unit automatically defaults to remote
mode whenever AC power is removed and
then applied. This is due to the presence of
the external interface board
.
5.5 BOILER MANAGEMENT SYSTEM
(BMS)
The BMS mode of operation is used in
conjunction with an AERCO boiler management
system and it is desired to operate multiple units
in the most efficient manner possible. Eight
boilers can be managed by a single AERCO
BMS 168 system using pulse width modulation.
The AERCO BMS monitors all system-related
parameters and modulates the firing rates of the
units. For BMS programming and operation see
the GF-108 BMS Operations Guide.
MENU
FUNCTION
SETTING
Secondary
Lore
re
Secondary
FUNC
Cont
Primary
Auto
OFF
Summary of Contents for Benchmark G-00-711
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