Honeywell W7100 Manual page 7

SPACE RESET
MECHANICAL
COOLING SETPOINT
ADJUSTABLE RESET
5 TO 20°F (3 TO 11K)
SPACE
M17920 TEMPERATURE
Fig. 7. Space reset algorithm.
T675
R
OUTDOOR AIR
THERMOSTAT
W
60 F [16 C]
1-ZONE CIRCUIT
2
ZONE 1 ZONE 3
T1 T3
ZONE 2
ZONE 4
T2
T4
4-ZONE AVERAGING RESET CIRCUIT
2
ZONE 1
ZONE 4
ZONE 7
T1
T4
ZONE 2
ZONE 8
ZONE 5
T2
T5
ZONE 3
ZONE 6
ZONE 9
T3
T6
9-ZONE AVERAGING RESET CIRCUIT
S963B1037 REMOTE SETPOINT POTENTIOMETER REQUIRED TO
1
PERMIT ADJUSTMENT OF RESET CONTROL POINT. (USE ONLY
WITH SPACE SENSORS. DO NOT USE WITH OUTDOOR SENSORS.)
2
ALL THERMOSTATS ARE T7047C1025 TYPE WIRED IN SERIES-
PARALLEL CONNECTION.
3
LOCK OUT RESET UNDER HIGH HUMIDITY CONDITIONS, SET
AT 60 F [16 C].
Fig. 8. Reset from space sensor wiring.
Outdoor Resets
Outdoor reset can be employed as an alternative to space
reset (C7031G1016). The advantages to outdoor reset are
that it is simple to apply with a minimum of field wiring. The
disadvantage is that outdoor air temperature can have little
effect on internal cooling load. This is best seen in the
common area of a large shopping mall, where the major
cooling loads are from solar heat, people and lighting.
FULL RESET
NO
RESET
3°F (2K) SETPOINT OF
BELOW RESET RESET SENSOR
S963B1037
1
TO W7100
TERMINALS
6 AND 7
3
S963B1037
1
T675
TO W7100
R
OUTDOOR AIR
TERMINALS
THERMOSTAT
W 6 AND 7
60 F [16 C]
S963B1037
1
T7
T675
TO W7100
R
OUTDOOR AIR
T8
TERMINALS
THERMOSTAT
6 AND 7
W
60 F [16 C]
T9
W7100G DISCHARGE WATER TEMPERATURE CONTROL
In applications where outdoor temperature does have a major
effect on the cooling load of a building, outdoor reset can have
the same advantages as space reset. Fig. 9 shows the
outdoor air reset operation (algorithm).
As the outdoor air temperature rises above 70°F (21°C),
the W7100G discharge water temperature setpoint is reset
downward. The reset amount is adjustable and it continues
until the outside air temperature reaches 90°F (32°C). At this
point, the discharge water temperature is being controlled at
the W7100G setpoint.
The outdoor air temperature reset strategy should only be
employed where outdoor air temperature has a major effect
on the building cooling load.
COOLING SETPOINT
W7100
SETPOINT
OUTDOOR AIR TEMPERATURE
M17919
Fig. 9. Outdoor reset schedule using C7031G1016.
W7100 LED Operation
The W7100 has one LED for each staged output. The LED
on the W7100 lights simultaneously as that stage relay
energizes. With the LED not lit, the stage cannot energize.
When the relay stage energizes, the normally closed contacts
open, and the normally open contacts close.
Reset Modifications
While the outdoor air and the indoor air reset algorithms are
software imbedded, it is possible to modify the outside air
reset start and stop temperatures. To do this, a resistor must
be placed in parallel with the outside air sensor (Rp) and a
resistor must be placed in series with the outside air sensor
(Rs). See Fig. 10.
OUTDOOR
AIR SENSOR
C7031G
M3962
Fig. 10. Reset modification schematic wiring diagram.
Use Table 3 to select the point at which no W7100 setpoint
reset will occur (T-High), and the point at which the W7100 will
be fully reset (T-Low). The resistor values for series (Rs) and
parallel (Rp) resistors are at the intersection of T-High and
T-Low. Indicated resistor values are standard resistors and
can be purchased at any local electronics store.
NOTE: Only the outdoor air reset can be modified in the
above described manner.
7
OUTDOOR RESET
FULL RESET
ADJUSTABLE RESET
5 TO 20°F (3 TO 11K)
T-LOW
RESISTOR
(R S )
SERIES
6
RESISTOR
(R P )
PARALLEL
7
NO
RESET
T-HIGH
W7100
TERMINALS
M17918
63-4046—1