Honeywell ERX, User Manual, Page: 31 / 84

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Digi-Span Fuel Switching Feature
An ERX connected to a Digi-Span module provides an automatic or manual fuel switching
function when item 340 is enabled. This feature requires ERX’s Pulser-A output to be connected
to the Digi-Span’s “Gas Override” terminal, the Pulser-B output connected to the “Oil Override”
terminal, and the common terminal ‘K’ connected to the Digi-Span common. When item code
340 is configured for Automatic mode, a pre-selected temperature at the Digi-Span module
determines which fuel is ‘switched on’. Item 340 may also be configured for either a manual
“Gas Override” or a manual “Oil Override”, which results in a continuous ON at one of the pulse
outputs channels.
Although not an original design consideration, there may be other applications that could make
use of a continuous ON from either pulse output channel besides the Digi-Span module. Care
must be taken to be certain that the connected device can be actuated with 5 mA of current, or
less. Regardless of the connected device, enabling item 340 places a heavier burden on the
battery, which will decrease battery life.