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Y594  
(
Multistage Thermostat Subbase)  
Package  
®
TRADELINE  
INSTALLATION INSTRUCTIONS  
APPLICATION  
Subbase Ratings  
These Y594G and Y594J combination packs are designed  
to meet the specific requirements of Carrier heat pump  
equipment. The Y594 packs are designed for 2 stage heat  
and 1 stage cool applications. The system switch is SUPL  
HT-HEAT-OFF-COOL or SUPL HT-ON-OFF. The fan  
switch is AUTO-ON. See Table 1 for model information  
and cross reference from Carrier part numbers.  
SWITCH RATING: 7.5A inrush, 2.5A running at 30 Vac.  
MOUNTING: Designed for mounting on wall or horizontal  
outlet box.  
Table 1. Heat Pump Thermostat/Subbase Combinations.  
Fig.  
No.  
Changeover  
OS No.  
Contains  
T874G2004 Y507J1011 T874G1055  
Q674L1892 Q674L1041  
Replaces Honeywell  
Replaces Carrier  
Mode  
Y594G1666  
7
6
5
4
99TZ90041106 HH07AT171  
HH93AZ175  
Manual  
changeover in  
cooling  
Y594G1674  
Y594J1001  
Y594J1019  
T874G2004 Y507J1003 T874G1055  
99TZ90040106 HH07AT171  
HH93AZ173  
Auto  
changeover in  
cooling  
Q674J1274  
Q674J1035  
T874J1069  
Q674L1900  
T874J1002  
Q674L1074 or  
Q674L1637  
HH07AT175 Manual  
HH93AZ186 or changeover in  
HH93AZ195 cooling  
HH07AT175 Auto  
HH93AZ183 or changeover in  
HH93AZ196 heating  
T874J1069  
Q674J1282  
T874J1002  
Q674J1068 or  
Q674J1159  
Thermostat Ratings  
SWITCHING: sealed mercury switch.  
SWITCH RATINGS:  
First Stage Heating and Cooling: 6.5A inrush, 1.5A  
maximum running at 25 Vac.  
Second Stage Heating and Cooling: 1.5A maximum  
running at 30 Vac.  
Changeover Switch: 6.5A inrush, 1.5A running at 25  
Vac.  
OPERATION  
The two stages of heat are energized sequentially with  
changes in temperature. Stage one comes on first; then if  
the temperature at the thermostat continues to move away  
from the setpoint, the second stage comes on. The  
thermostat is set with about 2°F (1°C) between stages. As  
the heating equipment runs and the temperature begins to  
move back toward the set point, stage 2 goes off first, then  
stage one.  
HEAT ANTICIPATOR:  
First Stage Heating and Cooling: fixed voltage type,  
Subbases include an LED (light emitting diode) indicator.  
This indicator lights to show that the heat pump cannot  
operate and the supplemental heat stage is providing all  
heating. This condition can occur in two instances; when  
the subbase system switch is set at SUPL. HT. and when  
the heat pump compressor has malfunctioned.  
1.0A.  
Second Stage Heating: adjustable, 0.10 to 1.2A; other  
models, fixed voltage type, 1.0A.  
TEMPERATURE SETTING RANGE: 42°F to 88°F (6°C to  
31°C).  
The LEDs are not field replaceable.  
Copyright © 1995 Honeywell Inc. •  
All Rights Reserved  
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Y594 (MULTISTAGE THERMOSTAT SUBBASE) PACKAGE  
RECYCLING NOTICE  
This control contains mercury in a sealed tube.  
Do not place control in the trash at the end of its  
useful life.  
Mounting and Wiring the Subbase  
Disconnect power supply to prevent electrical shock or  
equipment damage. All wiring must comply with local  
electrical codes and ordinances. Follow equipment  
manufacturer wiring instructions when available.  
If this control is replacing a control that contains  
mercury in a sealed tube, do not place your old  
control in the trash.  
Mount the subbase on a wall or horizontal outlet box. To  
mount it on a vertical outlet box, order Honeywell part no.  
1
96393A Cover Plate Assembly, which includes an  
Contact your local waste management authority for  
instructions regarding recycling and the proper  
disposal of this control, or of an old control  
containing mercury in a sealed tube.  
adapter ring with two screws for vertical outlet box  
mounting and a cover plate to cover marks on the wall.  
To install subbase, proceed as follows:  
Prepare a hole for the thermostat wires at the  
chosen location. Run wires to location.  
INSTALLATION  
Pull about 6 in. (152 mm) of wire through the hole.  
When Installing this Product…  
IMPORTANT  
Use 18 gauge, color-coded thermostat cable for  
Read these instructions carefully. Failure to follow  
them could damage the product or cause a hazard-  
ous condition.  
proper wiring.  
Check the ratings given in the instructions and on  
the product to make sure the product is suitable for  
your application.  
Installer must be a trained, experienced service  
technician.  
After installation is complete, check out product  
operation as provided in these instructions.  
If mounting the subbase on a vertical outlet box,  
install adapter ring with the two screws provided in  
the assembly. See Fig. 1.  
Pull wire through cover plate, if used, and subbase  
wire opening. Secure the cover plate and subbase  
with the two screws provided, but do not tighten  
down.  
Level the subbase using a spirit level. See Fig. 2.  
Tighten subbase mounting screws. The subbase  
mounting slots provide for minor out-of-level  
adjustments.  
CAUTION  
Disconnect power supply to prevent electrical  
shock or equipment damage.  
Run wires as close as possible to the sub-  
base. To prevent interference with the  
thermostat linkage, keep wire length to a  
minimum. Push excess wire back into the  
hole, and plug hole to prevent drafts from  
affecting thermostat operation.  
Do not overtighten thermostat captive  
mounting screws because damage to  
subbase threads can result.  
Do not short across coil terminals on relay.  
This may burn out the heat anticipator.  
Never install more than one wire per terminal  
unless factory-supplied jumper with spade  
terminal is used.  
IMPORTANT  
An incorrectly leveled subbase will cause the  
temperature control to deviate from setpoint  
Connect the system wires to the subbase. See  
Fig. 4-7. A letter is stamped near each terminal for  
identification. The terminal barrier permits straight or  
conventional wraparound wiring connections. See  
Fig. 3. Either method is acceptable. Run wires as  
close as possible to the subbase, keeping wire  
length to a minimum. Push excess wire back into  
hole. Plug hole to prevent drafts.  
IMPORTANT  
Thermostats are calibrated at the factory by using  
Mounting the Thermostat  
Remove the thermostat cover by pulling the bottom  
edge of the cover away from the base until it snaps  
free of the retaining posts.  
subbases mounted at true level. Inaccurate sub-  
base leveling will cause thermostat control  
deviation.  
NOTE: The cover is hinged at the top and must be  
removed by pulling out at the bottom.  
Location  
Install the thermostat about 5 ft (1.5m) above the floor in  
an area with good air circulation at average room  
temperatures.  
Carefully remove and discard the polystyrene  
packing insert that protects the mercury switches  
during shipment.  
Turn the thermostat over and locate the spring  
fingers that engage the subbase contacts. Make  
sure the spring fingers are NOT bent flat, preventing  
proper electrical contact with the subbase.  
Set adjustable heat anticipator indicators, if  
provided, as described in Setting the Heat  
Anticipator(s) section.  
Do not mount the thermostat where it may be affected by:  
drafts, or dead spots (no air movement) behind doors,  
in corners, and above or below shelves.  
hot or cold air from ducts.  
radiant heat from the sun, lights, or appliances.  
concealed pipes and chimneys.  
unheated or uncooled areas such as an outside wall  
behind the thermostat.  
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Y594 (MULTISTAGE THERMOSTAT SUBBASE) PACKAGE  
VERTICAL  
OUTLET  
BOX  
MOUNTING  
SCREWS (2)  
Note the tabs along the top inside edge of the  
thermostat base. The tabs fit into the subbase  
notches. Mount the thermostat on the subbase and  
tighten the captive mounting screws. See Fig. 1. Do  
not overtighten captive mounting screws. This can  
damage the threads in the subbase.  
Place the upper edge of the thermostat cover on the  
base and swing cover downward until it engages  
retaining posts on base. Tighten the locking cover  
screws if assembly is provided.  
1
COVER  
PLATE  
ADAPTER  
2
RING  
2
1
HORIZONTAL  
OUTLET  
BOX  
SETTING  
Setting the 2nd Stage (Y594G1666 and  
Y594G1674 Only) Heat Anticipator  
Set the adjustable heat anticipator to match its primary control  
current draw. If the primary control nameplate has no rating or  
if further adjustment is necessary, use the following procedure  
to measure the current draw of each stage:  
THERMOSTAT  
COOL  
THERMOSTAT  
COVER  
8
0
7
0
0
6
5
0
Remove thermostat from the subbase. Make sure  
the power is on.  
SUBBASE  
7
0
80  
6
0
EAT  
50  
H
Connect an ac ammeter of appropriate range  
between the heating terminals of the subbase:  
Stage 2: between W2 and R.  
SUBBASE  
MOUNTING SCREWS (2)  
5
0
60 70 80  
Move the system switch to HEAT or ON.  
After one minute, read the ammeter and record the  
reading.  
Remount the thermostat and use a ballpoint pen to  
set the adjustable heat anticipator(s) to match the  
reading(s) measured in step 4. See Fig. 8.  
CAPTIVE  
MOUNTING SCREWS (2)  
1
2
NOT INCLUDED WITH UNIT.  
ACCESSORY PARTS AVAILABLE (193121A).  
M6009  
Fig. 1. Installation of subbases and thermostat on  
outlet box.  
Temperature Setting  
Move the heating and cooling levers to the desired  
positions. The minimum differential between heating and  
cooling setpoints is 3°F (2°C). Some thermostat models  
have nonadjustable lever stops, which set the maximum  
heating control point at 68°F or 72°F (20°C or 22°C) and  
the minimum cooling control point at 78°F (26°C). Do not  
attempt to exceed these limits. Some models have only  
one lever for heating and cooling.  
TOP  
MOUNTING  
HOLES (2)  
WIRING  
TERMINAL  
THERMOSTAT  
CABLE OPENING  
SPIRIT LEVEL  
Subbase Setting  
Available subbase system switch positions vary by  
thermostat model. Positions control thermostat operation  
as follows:  
OFF: Heating and cooling systems are off. If the fan  
switch is at the AUTO position, the fan is also off.  
HEAT: Heating system is controlled by the thermostat.  
Cooling system is off.  
COOL: Cooling system is controlled by the thermostat.  
Heating system is off.  
MOUNTING  
HOLES (2)  
POST (2) FOR  
MOUNTING  
THERMOSTAT  
TO SPRING FINGER  
CONTACTS ON THE  
THERMOSTAT  
(
UP TO 12)  
M927  
ON: Thermostat automatically switches between heat  
and cool modes, depending on the indoor tempera-  
ture.  
Fig. 2. Leveling the subbase.  
SUPL. HT.: Supplemental heat is energized. Cooling  
system is off. Compressor cannot operate.  
FOR STRAIGHT  
INSERTION–  
STRIP 5/16 in. (8 mm)  
FOR WRAPAROUND–  
STRIP 7/16 in. (11 mm)  
Fan switching positions control fan operation as follows:  
ON: Fan operates continuously.  
AUTO: Fan operates with heat pump and supplemental  
heat as controlled by the thermostat.  
BARRIER  
SUBBASE TERMINAL SCREW  
M928  
Fig. 3. Wiring connections.  
3
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Y594 (MULTISTAGE THERMOSTAT SUBBASE) PACKAGE  
ON  
R
FAN  
G
AUTO  
CO  
1
0
8
12  
C1  
Y
9
11  
OFF  
ON  
O
SUPL.  
HEAT  
CO STAGE  
P
SUPL. HEAT  
ON  
E
L
H1  
3
2
C
4
6
H2  
W2  
X
ON  
5
SUPL. HEAT  
FIELD WIRING CONNECTION  
DENOTES CONNECTION POINT BETWEEN SUBBASE AND THERMOSTAT  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
L2  
(
HOT)  
1
R
FAN  
SWITCH  
FALL  
COMPRESSOR CONTACTOR  
Y
H1  
AUTO  
ON  
2
3
G
FAN RELAY  
W2  
HEAT RELAY 1  
H1 ANTICIPATOR  
H2 ANTICIPATOR  
OUTDOOR  
THERMOSTAT  
4
5
SUPL. HT.  
LED (RED)  
L
HEAT RELAY  
CONTACT 1  
HEAT RELAY 2  
H2 FALL  
C
E
6
8
HEAT RELAY  
CONTACT 2  
HEAT RELAY 3  
"X" RELAY  
RISE  
9
SYSTEM  
SWITCH  
X
P
CO  
C1 ANTICIPATOR  
"P" RELAY  
SUPL. HT.  
1
0
ON  
COOL CHANGEOVER  
VALVE  
OFF  
RISE  
CO  
C1  
11  
O
1
2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M4563  
Fig. 4. Y594J1019 Thermostat/Subbase switching and internal connections.  
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Y594 (MULTISTAGE THERMOSTAT SUBBASE) PACKAGE  
ON  
R
FAN  
G
AUTO  
C0  
10  
8
1
2
C1  
Y
COOL  
COOL  
9
O
P
OFF  
11  
C0 STAGE  
HEAT  
SUPL.  
HEAT  
SUPL. HEAT  
E
L
HEAT  
3
H1  
2
HEAT  
4
C
6
H2  
5
W2  
X
HEAT  
SUPL. HEAT  
FIELD WIRING CONNECTION  
DENOTES CONNECTION POINT BETWEEN SUBBASE AND THERMOSTAT  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
L2  
(
HOT)  
1
FALL  
FAN  
SWITCH  
R
H1  
COMPRESSOR CONTACTOR  
Y
2
3
AUTO  
ON  
G
H1  
FAN RELAY  
HEAT RELAY 1  
ANTICIPATOR  
2
4
W2  
H2  
OUTDOOR  
THERMOSTAT  
ANTICIPATOR  
SUPL. HT.  
LED (RED)  
FALL  
5
H2  
L
6
8
HEAT RELAY HEAT RELAY 2  
CONTACT 1  
SYSTEM  
SWITCH  
C
HEAT RELAY  
CONTACT 2  
RISE  
9
SUPL. HT.  
HEAT RELAY 3  
E
X
C1 ANTICIPATOR  
HEAT  
CO  
1
0
OFF  
"
X" RELAY  
COOL  
"P" RELAY  
RISE  
CO  
P
C1  
11  
O
COOL  
CHANGEOVER VALVE  
1
2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M4564  
Fig. 5. Y594J1001 Thermostat/Subbase switching and internal connections.  
5
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Y594 (MULTISTAGE THERMOSTAT SUBBASE) PACKAGE  
ON  
FAN  
R
G
AUTO  
C1  
8
Y
OFF  
ON  
10  
CO  
9
1
SUPL. HEAT  
O
ON  
4
H1  
H2  
2
ON  
E
SUPL. HEAT  
6
W2  
C
L
SUPL. HEAT  
FIELD WIRING CONNECTION  
SUPL. HEAT  
DENOTES CONNECTION POINT BETWEEN SUBBASE AND THERMOSTAT  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
COOL CHANGEOVER VALVE  
1
L1  
HOT)  
1
O
(
H1 ANTICIPATOR  
L2  
FAN  
SWITCH  
AUTO  
ON  
G
R
2
FAN RELAY  
H1  
OUTDOOR  
THERMOSTAT  
FALL  
H2  
4
6
W2  
EM. HT. RELAY 1  
H2 ANTICIPATOR  
EM. HT. RELAY EM. HT. RELAY 2  
CONTACT 1  
FALL  
SYSTEM  
SWITCH  
E
2
EM. HT. RELAY EM.HT.  
8
9
CONTACT 2  
RELAY 3  
CO  
C1 ANTICIPATOR  
L
RISE  
SUPL. HT.  
ON  
SUPL. HT.  
LED (RED)  
C
Y
OFF  
COMPRESSOR  
CONTACTOR 1  
C1  
10  
RISE  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
2
N.O. SWITCH INSTALLER ADDED, TO LIGHT EM. HT. LED  
WHEN COMPRESSOR OPERATION IS NOT NORMAL.  
M4565  
Fig. 6. Y594G1674 Thermostat/Subbase switching and internal connections.  
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Y594 (MULTISTAGE THERMOSTAT SUBBASE) PACKAGE  
ON  
R
FAN  
G
AUTO  
C1  
8
Y
1
0
CO  
9
COOL  
OFF  
HEAT  
SUPL. HEAT  
O
HEAT  
4
H1  
H2  
1
2
HEAT  
E
SUPL. HEAT  
6
W2  
C
L
SUPL. HEAT  
FIELD WIRING CONNECTION  
DENOTES CONNECTION POINT BETWEEN SUBBASE AND THERMOSTAT  
SUPL. HEAT  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
COOL CHANGEOVER VALVE  
O
1
L1  
HOT)  
1
2
(
H1 ANTICIPATOR  
L2  
FAN  
SWITCH  
AUTO  
ON  
G
R
FAN RELAY  
H1  
OUTDOOR  
THERMOSTAT  
FALL  
H2  
4
6
W2  
HEAT RELAY 1  
H2 ANTICIPATOR  
HEAT RELAY  
CONTACT 1  
HEAT RELAY 2  
FALL  
SYSTEM  
SWITCH  
E
2
HEAT RELAY HEAT RELAY 3  
CONTACT 2  
8
9
SUPL. HT.  
HEAT  
L
COMPRESSOR  
FAULT  
CO  
SUPL. HT.  
LED (RED)  
RISE  
C1 ANTICIPATOR  
OFF  
C
Y
1
0
COMPRESSOR  
CONTACTOR 1  
COOL  
C1 RISE  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
2
N.O. SWITCH INSTALLER ADDED, TO LIGHT EM. HT. LED  
WHEN COMPRESSOR OPERATION IS NOT NORMAL.  
M4566  
Fig. 7. Y594G1666 Thermostat/Subbase switching and internal connections.  
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Y594 (MULTISTAGE THERMOSTAT SUBBASE) PACKAGE  
LED Indication  
Set system switch on subbase at SUPL. HT. The SUPL.  
HT. LED should light. Simulate compressor failure and  
energize the system. The FAULT LED should light.  
CALIBRATION  
Thermostat  
These thermostats are accurately calibrated at the factory.  
They do not have provision for field calibration.  
1
.2.8  
STAGE TWO  
ANTICIPATOR  
HEATING CONTROL  
MOVE INDICATOR TO  
MATCH CURRENT RATING  
OF PRIMARY CONTROL  
Thermometer  
The thermometer in your thermostat has been accurately  
calibrated at the factory. The thermometer should only  
adjustment if it has been dropped or shifted due to  
mishandling.  
M4550  
Fig. 8. Adjustable heat anticipator shown.  
To switch positions, use thumb and index finger to slide  
lever to desired position. Switch lever must stop in detent  
directly over the desired function indicator mark for proper  
system operation.  
If the setpoint lever and the thermometer reading do not  
agree, use the following procedure:  
Remove the thermostat cover by pulling up from the  
bottom edge of the cover away from the base until it  
snaps free of the cover clip.  
CHECKOUT  
Heating  
Set the thermostat cover on a table near an  
accurate thermometer.  
Allow ten minutes for cover thermometer to sense  
area temperature; compare the readings. Be careful  
not the touch the thermometer or breathe on it.  
If the readings are the same, replace cover and put  
the system into operation.  
If the readings are different, insert a small screw-  
driver in the thermometer slot and turn it until the  
thermometers have the same reading. See Fig. 9.  
Replace thermostat cover and put the system into  
operation.  
Set the system switch on the subbase at HEAT or ON and  
the fan switch at AUTO. Move the heating lever on the  
thermostat about 10°F (6°C) above room temperature.  
Heating (both stages if two-stage thermostat) should start  
if there is no time delay or outdoor temperature limiting  
system, and the fan should come on. Move the heating  
lever about 10°F (6°C) below room temperature. Heating  
and fan should shut off.  
Cooling  
CAUTION  
Do not operate cooling if outdoor temperature is  
below 50°F (10°C). Refer to manufacturer recom-  
mendations.  
Set the system switch on the subbase to COOL or ON and  
the fan switch to AUTO. Move the cooling lever on the  
thermostat about 10°F (6°C) below room temperature.  
Cooling and fan should start. Move the cooling lever about  
10°F (6°C) above room temperature. Cooling and fan  
should stop.  
Fan  
Set the fan switch to ON. Move the system switch to  
different positions; the fan should run continuously. Move  
the fan switch to AUTO. Move the system switch to  
different positions. Fan operation is controlled with the  
heating or cooling system.  
M5070  
Fig. 9. Thermometer calibration.  
Home and Building Control  
Home and Building Control  
Honeywell International, Inc.  
Honeywell Limited-Honeywell Limitée  
35 Dynamic Drive  
1
985 Douglas Drive North  
Golden Valley, MN 55422  
Scarborough, Ontario  
M1V 4Z9  
69-0920  
J.H. 5-95  
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