Honeywell W7750A Manual

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EXCEL 10 W7750A,B,C CONSTANT VOLUME AHU CONTROLLER

57 74-2958—1

DestB

y

pass - Has possible states: B

y

pass On,

B

y

pass Off or Not Assi

g

ned

(

not active

)

.

This input places the controller in an

untimed

b

y

pass state or turns off the

b

y

pass mode. This source is second in

priorit

y

to DestManOcc under the same

arbitration schemes mentioned above.

Override Button -The wall module Override pushbutton

can command status of B

y

pass,

Continuous Unoccupied and Not

Assi

g

ned. This source has the lowest

priorit

y

status in the above mentioned

schemes. The above mention sources

of override must be either Not Assi

g

ned

or Off before the Override pushbutton

affects the manual override status in the

Network Wins scheme. All actions, in

this case, taken from the Override

pushbutton are locked out.

B

y

pass status is a controller-timed

event whose duration is set in B

y

pTime.

Upon expiration of the timer, the status

returns to Not Assi

g

ned. The status of

this input can be overridden with the

receipt of Not Assi

g

ned from

DestManOcc. This, in effect, cancels a

timed b

y

pass or a continuous

unoccupied mode.

The Override pushbutton can be

confi

g

ured as Normal

(

all of the above

mentioned states are possible

)

, B

y

pass

Onl

y

(

B

y

pass and Not Assi

g

ned onl

y)

or

None

(

effectivel

y

Disablin

g

the Override

pushbutton

)

.

TIME CLOCK (Occ_Time_Clock)

OccTimeClock is the state of the di

g

ital input confi

g

ured and

wired to a time clock. When the di

g

ital input is detected to be

Closed

(

Occupied

)

, the scheduled occupanc

y

will be

OC_OCCUPIED. If the detected state of the di

g

ital input is

Open

(

Unoccupied

)

, then the scheduled occupanc

y

will be

OC_UNOCCUPIED. If the Occ_Time_Clock is not confi

g

ured,

then either the DestSchedOcc network input received from a

central control or the time clock that is broadcast from a

Sched_Master confi

g

ured W7750, controls the occupied

mode.

SCHEDULE MASTER (Sched_Master)

Sched_Master is the state of a di

g

ital input that is confi

g

ured

and wired to the W7750. If the Sched_Master input is closed

(

input shorted

)

, the node is the schedule master and the state

of the locall

y

connected time clock will be broadcast out over

the L

ON

W

ORKS

Bus to the other W7750 controllers. If the

Sched_Master input is open, then the node is not a schedule

master and the local time clock will not be sent out over the

L

ON

W

ORKS

Bus even if the time clock input is confi

g

ured.

However, the DestSchedOcc network input received from a

central control has a hi

g

her priorit

y

than the local time clock,

and therefore overrides the local time clock. The W7750

controllers automaticall

y

bind without the need for a

confi

g

uration tool.

SETPOINT RAMPING

The W7750 Controller incorporates a rampin

g

feature that

g

raduall

y

chan

g

es the space setpoints between occupanc

y

modes. This feature is onl

y

operational if the network variable

inputs DestSchedOcc, TodEventNext, and Time Until Next

Chan

g

e Of State

(

TUNCOS

)

are bein

g

used to chan

g

e the

W7750 Occupanc

y

mode. The applicable Setpoints are

OaTempMinHtRamp, OaTempMaxHtRamp, MinHtRamp and

MaxHtRamp

(

for HEAT mode operation

)

, and

OaTempMinClRamp, OaTempMaxClRamp, MinClRamp and

MaxClRamp

(

for the COOL mode operation

)

. See Fi

g

. 46 for a

pictorial representation of how these setpoints interact.

Durin

g

recover

y

operation, the setpoint chan

g

es at a rate in

de

g

rees per hour dependin

g

on the outdoor air temperature. If

there is no outdoor air temperature sensor available, then

MinHtRamp is used as the recover

y

rate.

Fig. 46. Setpoint ramping parameters with ramp rate

calculation.

NOTE: Recover

y

rampin

g

applies between scheduled

heatin

g

or coolin

g

setpoint chan

g

es from

UNOCCUPIED to STANDBY, UNOCCUPIED to

OCCUPIED, and STANDBY to OCCUPIED.

Scheduled setpoint chan

g

es from OCCUPIED to

UNOCCUPIED or OCCUPIED to STANDBY do not

use a ramped setpoint but instead use a step chan

g

e

in setpoint. Recover

y

ramps be

g

in before the next

scheduled occupanc

y

time and are ramped from the

setpoint for the existin

g

scheduled occupanc

y

state

to the setpoint for the next occupanc

y

state.

RECOVERY RAMPING FOR HEAT PUMP SYSTEMS

When the node is controllin

g

heat pump e

q

uipment, durin

g

the

recover

y

ramps, the heatin

g

setpoint is split into a heat pump

setpoint

(

for compressors

)

and an auxiliar

y

heat setpoint

(

for

auxiliar

y

heat sta

g

es

)

. The heat pump setpoint is a step

chan

g

e at the recover

y

time prior to the OCCUPIED time.

Recover

y

time is computed from the confi

g

ured heat recover

y

ramp rate. The recover

y

time is calculated:

Recover

y

time =

(

OCC setpoint - current setpoint

)

/ramp rate

See Fi

g

. 47 for the various setpoints.

HEAT RECOVERY

RAMP RATE

(DEGREES/HOUR)

MaxHtRam

MinHtRam

OaTempMinHtRa OaTempMaxHtRam

OUTDOOR AIR

TEMPERATURE

M10109