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C8-1 DIAGRAM WITH D8 DIAGRAM
Night Setback (optional field installed)
20- Optional field installed time clock and night relay K11 must be connected for night setback op
eration.
21- Blower B3 operates only during a heating demand when night thermostat is closed. Energized
by relay K25 in unit.
22- When clock contacts close, relays K11 and K38 energize.
23- Contacts K38-1 close to energize setback resistor R4.
Contacts K38-2 close to energize setup resistor R5.
Contacts K38-3 open to energize blower B3 on demand only.
During night operation when contacts K38-3 are open. blower B3 operates only on demand
powered through relays K25 (for heat) or K37 (for cool). Outdoor air dampers are held closed
by contacts K11-2 remaining open (not shown).
24- A1 terminal 1 feeds 20VDC at all times to A2 terminal 1 and contacts K38-1 and K38-2 (source
of voltage for resistors in relay kit).
25- When heating demand is present during unoccupied periods, 20VDC feeds through K38-1
and R4. R4 alters the voltage. A2 terminal 6 receives that altered voltage and uses it to shift
the unoccupied setpoint. R4's value, 3.6K ohms, shifts the unoccupied setpoint down 10F.
For example, if heat lever of A2 is set at 75F, the unoccupied setpoint for first stage opera
tion is 65F.
26- When cooling demand is present during unoccupied periods, 20VDC feeds through K38-2
and R5. R5 alters the voltage. A2 terminal 8 receives that altered voltage and uses it to shift
the unoccupied setpoint. R5's value, 1.2K ohms, locks out cooling in unoccupied mode.
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