Honeywell W7750A Manual

A SERVICE OF

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EXCEL 10 W7750A,B,C CONSTANT VOLUME AHU CONTROLLER

74-2958—156

Fig. 45. LED and Bypass pushbutton operation.

STANDBY MODE (StatusOcySen)

The di

g

ital input for an occupanc

y

sensor

(

usuall

y

a motion

detector or possibl

y

a time clock

)

provides the controller with a

means to enter an ener

gy

-savin

g

Standb

y

mode whenever

people are not in the room. Standb

y

mode occurs when the

scheduled occupanc

y

is Occupied, and the occupanc

y

sensor

detects no people currentl

y

in the room

(

di

g

ital input contacts

Closed means people are in the room, and contacts Open

means the room is Unoccupied

)

. When in Standb

y

mode, the

Excel 10 W7750 Controller uses the Standb

y

Coolin

g

Setpoint

for coolin

g

(

CoolStb

y

Spt

)

, or the Standb

y

Heatin

g

Setpoint for

Heatin

g

(

HeatStb

y

Spt

)

as the Actual Space Temperature

Setpoint. The occupanc

y

sensor si

g

nal can also be a network

input from another L

ON

W

ORKS

Bus device, so that no ph

y

sical

sensor is re

q

uired at the receivin

g

W7750 Controller.

IMPORTANT

When the W7750 Controller is in Standby mode, the

economizer minimum position setting is

not

observed. This means the fresh air dampers will go

fully closed if there is no call for cooling.

CONTINUOUS UNOCCUPIED MODE

This mode is entered when a wall module is confi

g

ured with a

B

y

pass pushbutton that was pressed for four to seven

seconds causin

g

the wall module LED/LCD to blink. This

mode can also be entered via a network command

(

ManualOcc set to Unoccupied

)

. If the controller is in this

mode, it reverts to the Unoccupied setpoints for temperature

control, and the economizer does not observe its minimum

position settin

g

. The controller remains in this mode

indefinitel

y

until the B

y

pass pushbutton is pressed to exit the

mode or a network command is sent to clear the mode. A

confi

g

uration parameter is available to disable wall-module

initiation of Continuous Unoccupied mode

(

OvrdT

y

pe

)

.

OCCUPANCY MODE AND MANUAL OVERRIDE ARBITRATION

The W7750 has multiple sources for occupanc

y

schedule

information and, therefore, it emplo

y

s an arbitration scheme to

determine the current actual mode. Time-of-da

y

(

TOD

)

schedule status comes from two sources, a confi

g

ured di

g

ital

input for OccTimeClock or the DestSchedOcc network input

received from a central control. If the di

g

ital input source is

confi

g

ured, it has hi

g

hest priorit

y

and determines the

Occupanc

y

mode. This di

g

ital input is either ON

(

shorted =

occupied

)

, OFF

(

open = unoccupied

)

, or not active

(

not

confi

g

ured

)

; otherwise, the status is determined b

y

the

DestSchedOcc input from the network source. The

DestSchedOcc has three possible states, occupied,

unoccupied or standb

y

.

Manual Override Status can be derived from three sources

and

g

overned b

y

two selectable arbitration schemes. The two

schemes are:

• Network Wins or Last-in Wins, as set in OvrdPriorit

y

.

The three sources of manual override status are:

DestManOcc - Has possible states: Occupied,

Unoccupied, B

y

pass, Standb

y

and Not

Assi

g

ned

(

not active

)

. This input source

has the hi

g

hest priorit

y

in determinin

g

manual override status for a Network

Wins arbitration scheme, and in the

event there is more than one source

chan

g

e at a time in the Last-in Wins

arbitration scheme. Here, b

y

pass

initiates a self-timed b

y

pass of the

control unit and expires upon

completion of the defined timed period.

The controller then treats the b

y

pass

status of this input as Not Assi

g

ned until

the next chan

g

e in status.

M8483A

RESET

NOT ASSIGNED

(LED OFF)

PRESS FOR ONE

TO FOUR SECONDS

BYPASS OCCUPIED

(LED ON)

BYPASS

TIMEOUT

PRESS FOR FOUR

TO SEVEN SECONDS

PRESS FOR LESS

THAN ONE SECOND

UNOCCUPIED

(LED BLINK)

PRESS FOR LESS THAN ONE SECOND

PRESS FOR MORE THAN SEVEN SECONDS