AERCO BMS 168 - Manual (Page 41)

4.4.8 AUX RELAY
This key is used to display or change the
firing rate at which the Auxiliary Relay
opens and closes. The Auxiliary Relay is
typically used with AERCO’s Combination
Control Panel (CCP) system or to start an
auxiliary boiler for use under peak load
conditions. If this boiler is of the non-
condensing type, the OFF firing rate
percentage must be high enough to prevent
the boiler from operation in condensing
mode.
Pressing the AUX RELAY key once
displays the firing rate percentage at which
the relay opens (AUX RELAY OPEN). The
default value of 45% is acceptable for a
CCP system. However, to run another non-
condensing boiler, this percentage may
need to be changed to approximately 70%.
The displayed percentage can be changed
in 1% increments from 1 to 99%.
Pressing the AUX RELAY key again
displays the firing rate percentage at which
the relay closes (AUX RELAY CLOSE). Two
options are available for this function: 100%
FIRING RATE, or 100% AND OFF
(default). Pressing the ▲ or ▼ arrow key
will toggle the display. If 100%
FIRING
RATE is selected, the Auxiliary Relay
contacts close when the BMS indicates that
all boilers are at a 100% firing rate. If the
default setting of 100% AND OFF is
selected, the Auxiliary contacts close when
the BMS indicates that all boilers are at a
100% firing rate
,
or when the BMS
determines that all boilers are off. The off-
state is when each boiler has either faulted,
or someone has pressed the off button on
the boilers. This function allows a boiler that
is wired to the Auxiliary Relay contacts to
fire when all of the other boilers have faulted
or have been turned off.
When in Combination Control Panel (CCP)
mode, care must be taken to ensure that the
AUX
RELAY OPEN percentage is set so
that the system does not oscillate turning
boilers on and off. A maximum open
percentage of 45% is recommended for
Combination Control mode. If using the
AUX contacts to fire an auxiliary boiler, the
recommended open percentage is 70%.
4.4.9 ▲ and ▼ Arrow Keys
These keys are used to increment (▲) or
decrement (▼) the displayed variable, or
toggle the display through available options.
Pressing and holding these keys will
increment or decrement the displayed value
at a rapid rate.
4.4.10 ON and OFF Keys
Pressing and releasing the ON or OFF key
enables or disables the BMS. In addition,
the corresponding LED will light when the
corresponding key is pressed.
4.4.11 CONFIG SYS
When the CONFIG SYS key LED is lit,
pressing this key will exit the System
Configuration Mode and place the BMS in
the Normal Mode. When this occurs, the
display will show HEADER TEMP (°F)
which is the default Normal Mode display.
See paragraph 4.2 for key functions in
Normal Mode.
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