Honeywell AUTOMATIC CONTROL SI Edition User Manual

ENGINEERING MANUAL OF AUTOMATIC CONTROL
AIR HANDLING SYSTEM CONTROL APPLICATIONS
221
ECONOMIZER CYCLE CONTROL OF SPACE TEMPERATURE WITH SUPPLY AIR
TEMPERATURE SETPOINT RESET
Functional Description
PSYCHROMETRIC ASPECTS
In the following chart it is assumed that:
1. The manual positioning setpoint value provides 25
percent minimum OA.
2. The MA controller is set at 13°C.
3. The OA controller closes the OA damper to the minimum
position when OA temperature is 27°C.
4. RA condition is 24°C DB and 15°C WB for winter; 27°C
DB and 18°C WB for summer.
5. OA condition is 1.5°C DB and –1.5°C WB for winter;
38°C DB and 23.5°C WB for summer.
6. Other components exist in the complete system which
hold the RA at the desired condition.
7. The desired MA temperature can be maintained during
economizer periods until the OA temperature falls below
the temperature at which only minimum OA is admitted
if the OA is less than 13°C.
The following results are obtained:
Item
No. Explanation
1 At OA temperatures below -26°C DB (25
percent OA set by manual positioning setpoint
value), the MA condition lies to the left of the
13°C DB line.
2 As the OA temperature varies between –26°C
and 13°C, MA conditions lie on the 13°C
DB line.
3 As the OA temperature varies between 13°C
and 24°C, 100 percent OA is admitted and
the MA lies in the area between 13°C and
24°C DB.
4 As the OA temperature rises above 27°C DB,
the system operates on 25 percent OA and
the MA temperature varies from 35°C to
29.5°C DB.
OA
22
ECONOMIZER DECISION.
REFER TO PREVIOUS
ECONOMIZER OPTIONS
OA MINIMUM SETPOINT
(NOTE: THE TEST AND BALANCE INITIAL VALUE
FOR PROPER VENTILATION IS 22)
M15158
12
14
11
CONTROL
PROGRAM
83
EA
SAMA
RA
ON
ON
15
5 1
4
2
13
8
3
7
10
9
6
83
NORMAL
24
13
MIXED AIR
TEMPERATURE
RESET SCHEDULE
SPACE
TEMPERATURE
SUPPLY AIR
TEMPERATURE
SETPOINT
SPACE
COOLING
DEMAND
0
100
23.5
23.5
15
C3237
MA WINTER
RA WINTER
24°C DB, 15°C WB
RA SUMMER
27°C DB, 18°C WB
MA SUMMER
OA SUMMER
38°C DB, 23.5°C WB
27°C DB OA
CONTROLLER
SETPOINT
1
2
3
4
OA WINTER
1.5°C DB, -1.5°C WB
13°C DB MA
CONTROLLER
SETPOINT

Honeywell AUTOMATIC CONTROL SI Edition Specifications

General

Brand	Honeywell
Model	AUTOMATIC CONTROL SI Edition
Category	Control Systems
Language	English