Honeywell T8621A User Manual Download Page 7

SYSTEM

PRESS     LOOK FOR THIS RESPONSE

SWITCH

THIS

KEY

KEY

POSITION

KEY

DOWN

RELEASED

OFF

03

Blank

07

Blank

15

Blank

COOL or

15

1st stage cooling,

AUTO (with

fan and SYSTEM

fan in AUTO)

LED on.

15

2nd stage cooling
also on.

15

2nd stage cooling off.

15

1st stage cooling, fan
and SYSTEM LED off.

NOTE: If single-stage cooling system, press key twice

instead of 4 times; once to turn cooling, fan and SYS-
TEM LED on, second time to turn off.

OFF

06

Blank

02

Blank

05

Blank

04

Blank

01

Blank

00

Blank

(CHECK

12

See note   A

EACH
POSITION)
OFF

08

Blank

13

Microprocessor mask
no. and revision no.

09

Blank

14

Blank

HEAT or

14

1st stage heating and

AUTO    1

SYSTEM LED on.

14

2nd stage heating
also on.

14

2nd stage heating off.

14

1st stage heating and
SYSTEM LED off.

NOTE: If single-stage heating system, press key twice

instead of 4 times; once to turn heating and SYSTEM
LED on, second time to turn off.

OFF

10

Blank

11

Normal operating
display.

1

For electric heat fan operation—The fan will operate
with the heating system when fan switch is in AUTO.

A

HEAT displayed when system switch is in HEAT,
COOL when in COOL, HEAT and COOL when in
AUTO, neither when in OFF. Also, a four-digit code is
displayed, with each digit explained below.

7

69-0330—3

Fig. 13—All segments on display.

2. Set system switch to OFF. Press AHEAD and BACK

and PRESENT SETTING keys at the same time to enter
self-test.

3. Press each key as listed below, and look for response

listed as key is held down and released.

COOLING

CAUTION

Do not operate cooling if outdoor temperature is
below 50

°

 F [10

°

 C]. Refer to manufacturer’s recom-

mendations.

NOTE: When cooling setting is changed, thermostat will

wait up to 5 minutes before turning on the cooling
equipment. This delay protects the compressor.

Move the system switch to COOL and the fan switch to

AUTO. Press COOLER key until the setting is about 10

°

 F

[6

°

 C] below room temperature. The cooling equipment and

fan should start. Press WARMER key until the setting is
about 10

°

F [6

°

C] above room temperature. The cooling

equipment and fan should stop.

NOTE: On an AUTO changeover thermostat, the heating

temperature must be set at least 3

°

 F [2

°

 C] below the

cooling temperature, or display will flash.

FAN

Move the system switch to OFF, and the fan switch to

ON. The fan should run continuously. When the fan switch
is in the AUTO position, fan operates directly with the
cooling system, and also with heating system on some
models.

INSTALLER SELF-TEST (optional)

IMPORTANT

AC power must be present on thermostat to con-
duct self-test. Relays will not toggle, codes will not
be present and thermostat will not manually exit
self-test without ac power.

Five-minute time delay on cooling does not func-
tion during self-test.

Perform the following test as a check of all thermostat

functions. If thermostat does not respond as indicated,
thermostat must be replaced.

1. Press AHEAD and BACK keys at the same time.

While holding keys down, all segments of the display should
be on (Fig. 13).

M525A

AM

SUN
MORNING

REPL

BAT

SET
PT

ROOM

PM

OUTDOOR

TUE WED THU FRI SAT TEMPORARY

MON

MIDDAY EVENING NIGHT COOL ON    HEAT ON

SKIP

NEXT

PERIOD

PRESENT

SETTING

PRESENT

SETTING

PRESENT

SETTING

PRESENT

SETTING

PRESENT

SETTING

SET

PRESENT
DAY/TIME

DAY

AHEAD

BACK

SET

PRESENT
DAY/TIME

SET

PRESENT
DAY/TIME

SET

PRESENT
DAY/TIME

SET

PRESENT
DAY/TIME

CHANGE

TO LAST
PERIOD

COOLER

WARMER

COPY

FROM

COPY

TO

PERIOD

CANCEL

PERIOD

SET

HEAT/COOL

HOLD

TEMP

RUN

PROGRAM

Summary of Contents for T8621A

Page 1: ...surface Thread wires through the center opening of the subbase Then mount the subbase using two screws provided Gently tighten screws level top surface of subbase then securely tighten screws WHEN INSTALLING THIS PRODUCT 1 Read these instructions carefully Failure to follow them could damage the product or cause a hazardous condition 2 Check the ratings on the product to make sure the product is s...

Page 2: ...rews are provided on the back of the thermostat Correct setting of these screws will provide optimum room temperature control NOTE MOST APPLICATIONS WILL NOT REQUIRE A CHANGE IN CYCLE RATE Fig 4 T8621A 1 stage heat 1 stage cool thermostat with HEAT AUTO COOL OFF system and AUTO ON fan switching WIRES THROUGH WALL OPENING WALL WALL ANCHORS 2 SUBBASE MOUNTING HOLES MOUNTING SCREWS 2 M846 FOR STRAIGH...

Page 3: ... SUPPLY 2 1 C2 C1 L1 HOT L2 1 2 1 POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED FOR SINGLE TRANSFORMER SYSTEM JUMPER R AND RC NOMINAL 24 Vac POWER MUST BE PRESENT BETWEEN R AND C FOR THERMOSTAT OPERATION 2 3 3 HIGH LIMIT M1575 SYSTEM TRANSFORMER R C W1 W2 Y2 Y1 G RC FAN RELAY HIGH LIMIT HIGH LIMIT L1 HOT L2 HEAT AUTO COOL SYSTEM SWITCH AUTO ON FAN SWITCH POWER SUPPLY PR...

Page 4: ...3 4 1 2 3 POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED FOR GAS OR OIL APPLICATIONS OR ELECTRIC HEAT APPLICATIONS WHERE THE FAN OPERATION IS CONTROLLED INDEPENDENTLY OF THE THERMOSTAT AUTO FAN OPERATES WITH Y1 ONLY TWO TRANSFORMERS MAY BE USED SET SWITCH TO NONELECTRIC POSITION SYSTEM SWITCH FAN SWITCH AUTO ON OFF HEAT COOL STAGE 1 HEAT RELAY STAGE 2 HEAT RELAY STAGE 2 ...

Page 5: ...poweroutage Batteriesare included with thermostat Install batteries in back of thermo stat as shown in Fig 11 Without battery backup the program will remain about 30 seconds in event of power loss IMPORTANT When batteries are first installed the display will flash 1 00 PM and 32 or 0 The temperature display will stay at 32 or 0 until the thermostat is powered from the system wiring Fig 11 Battery ...

Page 6: ...l system power is on check voltage between R and C should be 24 to 30 Vac SETTING DAY AND TIME Restore 24 V power to the thermostat When power is applied to the thermostat the display will read 1 00 PM and roomtemperature Itwillgooffforafewseconds thenbegin to flash on and off Set present day and time Press Press to set the current day Each press of the DAY key advances the display one day Press T...

Page 7: ...ng setting is changed thermostat will wait up to 5 minutes before turning on the cooling equipment This delay protects the compressor Move the system switch to COOL and the fan switch to AUTO Press COOLER key until the setting is about 10 F 6 C below room temperature The cooling equipment and fan should start Press WARMER key until the setting is about 10 F 6 C above room temperature The cooling e...

Page 8: ...y MN 55422 4386 Spain Taiwan United Kingdom U S A CANADA 740 Ellesmere Road Scarborough Ontario M1P 2V9 PRINTED IN TAIWAN R O C QUALITY IS KEY CYCLE RATE SETTING CPH at 50 on time for FIRST stage 1 on 1 heat models DIGIT stage 2 on 2 heat models 0 1 1 3 2 9 3 6 SYSTEM THIRD MANUAL OR AUTO SWITCH DIGIT CHANGEOVER POSITION 0 Manual HEAT or OFF 1 Auto HEAT or OFF 3 Auto AUTO 4 Manual COOL 5 Auto COOL...

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