Reznor YDSA Unit Installation Manual - Manual (Page 52)

Form I-Y, P/N 273646R6, Page 52
9.2.3 Heat Section Controls
The ignition sequence depends on whether the heat section has staged control (YDSA
only) or modulation control (YDSA, YDHA, or YDMA).
FIGURE 25 -
Gas Heat
Control
Locations
The gas heat section controls are located on the left wall of the gas heat section.
75VA Transformer
Terminals
Venter Motor
Speed Controller
(AG73 & AG74)
Pressure Switches for Single Heat Section or
Right (first) Furnace in a Dual Heat Section
(See descriptions left.)
Relay (communicates with
the system controller)
DSI Control Module for
Single Heat Section or
Right (first) Furnace in
a Dual Heat Section
Pressure Switches for the Left (second)
Furnace in a Dual Heat Section
(See descriptions left.)
DSI Control Module for
the Left (second) Furnace
in a Dual Heat Section
Low Speed
Venter Switch
(AG73 & AG74)
Blocked Condensate
Switch (High Efficiency,
Condensing Furnace)
High Venter
(Combustion
Air) Switch
Blocked Condensate
Switch (High Efficiency,
Condensing Furnace)
High Venter
(Combustion
Air) Switch
Relay (communicates with
the system controller)
Staged Gas Control
(2-stage, Option AG71
or 4-stage, Option AG72
- apply to Model YDSA
only)
Sequence of Operation
1) W1 is energized and the controller verifies that the pressure switches are open.
2) Inducer (venter) is energized for pre-purge and the controller verifies that the low
pressure switch is closed.
3) After the pre-purge period has elapsed (20 seconds), the controller energizes the
trial for ignition period (17 seconds).
4) If W2 is energized, the high gas output will energize.
5) After W1 and W2 are de-energized, the controller will run the blower-off delay (120
seconds) and return to standby mode.
Modulating Gas Control
(5:1, Option AG73 or
10:1, Option AG74 -
apply to all models)
Sequence of Operation
1) W1 is energized and the controller verifies that the pressure switches are open.
2) Inducer (venter) is energized for pre-purge and the controller verifies that the low
and high pressure switches are closed.
3) After the pre-purge period has elapsed (20 seconds), the controller energizes the
trial for ignition period (17 seconds).
4) If W2 is energized, the high gas output will energize and the control will check for
high pressure switch input.
5) After W1 and W2 are de-energized, the controller will run the blower-off delay (120
seconds) and return to standby mode.
9.2 Gas Heat Section (cont’d)
9.0 Optional Equipment including Heat Sections (cont’d)