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C14-1 DIAGRAM WITH D5 DIAGRAM
Enthalpy Low (outside air can be used for cooling):
16- Initial cool demand (voltage ramp from A2 terminal4) closes C1.
17- Enthalpy control A6 has determined that outside air can be used for cooling and has switched
1K and 2K internally.
18- Cooling demand is routed through enthalpy control to energize internal relay 1S. Internal con
tacts 1S1 close to complete a circuit through damper motor terminals T and T1. Simultaneous
ly, cooling demand energizes relay K37.
19- When a voltage is applied across terminals T and T1 of damper motor, the damper motor ener
gizes and outdoor dampers open. Supply air sensor R1 varies the voltage across T and T1
and the outdoor air dampers adjust accordingly. First stage cooling is provided by outdoor air.
20- Contacts K37-1 close to energize blower on cooling speed.
21- Additional cooling demand closes C2. Demand is routed through enthalpy control terminals 3
and 5 to energize the compressor and relay K55. The compressor provides all additional cool
ing.
22- Contacts K55-1 switch to energize relay K37. Contacts K37-1 close to energize blower on
cooling speed (no affect).
Enthalpy High (outside air cannot be used for cooling):
23- Enthalpy control internal relays 1K and 2K switch. Internal relay 1S is deenergized and 1S1
opens. Outdoor air dampers close to minimum position during blower operation.
24- Cooling demand is sent from A1 terminal C1 through enthalpy control terminals 1 and 2 and
through enthalpy control terminal 5 to energize the compressor and relays K37 and K55. The
compressor handles all cooling demand.
25- Contacts K37-1 close to energize blower on cooling speed. Simultaneously, contacts K55-1
switch (no affect). Blower is energized on cooling speed.
26- Blower demand energizes relay K3 in unit. Contacts K3-1 close to energize the blower and
contacts K3-2 close to energize the economizer. When 24VAC is applied between damper
motor terminal TR and TR1, outdoor dampers open to minimum position.
Night Setback (optional field installed)
27- Optional field installed time clock, night thermostat S12 and night relay kit K11 must be con
nected for night setback operation.
28- Blower B3 operates only during a heating demand.
29- When clock contacts close, relays K11, K38 and K42 all energize.
30- K42-1 opens to deenergize relay K41.
31- K41-3 opens to drive dampers closed.
32- 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 which remain open.
33- A1 terminal 1 feeds 20VDC at all times to A2 terminal 1 and contacts K38-1 and K38-2.
34- When heating demand is present during unoccupied periods, 20VDC feeds through K38-1
and R4. R4 alters the voltage. A2 terminal 6 receives 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 operation is
65F.
35- 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.
Morning Warm-Up:
36- Shortly before the building is to be occupied, time clock CMC3-1 contacts open.
37- Relays K38, K42 and K11 disengage.
38- Contacts K42-1 open. Contacts K11-2 close to allow outdoor dampers to open. Note that
dampers remain closed until relays K3 and K41 are energized.
39- Since contacts K40-1 are normally closed and contacts K42-1 have just switched closed, tim
er DL7 is energized. Timer DL7 is normally open and closes 30 seconds after being energized.
40- If heat demand H1 reaches relay K40 before delay DL7 closes, contacts K40-1 open, delay
DL7 loses power and resets and the economizer locks out for the first heat demand by relay
K41 (contacts K41-3 remain open). If heat demand H1 reaches relay K40 after delay DL7
closes, relay K41 energizes and the economizer locks in for the day until night setback.
41- When first heat demand is satisfied, relay K40 disengages and relay contacts K40-1 close.
Relay contacts K42-1 are already closed (clock contacts open). Time delay DL7 begins 30
second count. If a second heat demand H1 reaches relay K42 within 30 seconds, delay DL7
loses power , resets and steps 41 and 42 repeat. If a second heat demand H1 does not reach
relay K42 within 30 seconds, time delay DL7 contacts close and relay K41 energizes.
42- When relay K41 energizes, the economizer operates normally, controlled by relay K3:
Contacts K41-1 close to lock in economizer operation until night setback.
Contacts K41-2 open (not used).
Contacts K41-3 close to allow power to the economizer.
Contacts K41-4 close (not used).
43- Once energized, relay K41 locks in and the economizer operates until relay K42 is ener
gized by night setback (contacts K42-1 open to disengage relay K41).
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