Honeywell Y594 User Manual
Y594
(Multistage Thermostat Subbase)
TRADELINE
®
APPLICATION
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.
Table 1. Heat Pump Thermostat/Subbase Combinations.
OS No.
Y594G1666 7 T874G2004
Y594G1674 6 T874G2004
Y594J1001 5 T874J1069
Y594J1019 4 T874J1069
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.
HEAT ANTICIPATOR:
First Stage Heating and Cooling: fixed voltage type,
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).
Fig.
No. Contains Replaces Honeywell Replaces Carrier
Q674L1892
Q674J1274
Q674L1900
Q674J1282
Y507J1011 T874G1055
Y507J1003 T874G1055
Q674L1041
Q674J1035
— T874J1002
Q674L1074 or
Q674L1637
— T874J1002
Q674J1068 or
Q674J1159
Package
INSTALLATION INSTRUCTIONS
Subbase Ratings
SWITCH RATING: 7.5A inrush, 2.5A running at 30 Vac.
MOUNTING: Designed for mounting on wall or horizontal
outlet box.
Changeover
Mode
99TZ90041106 HH07AT171
99TZ90040106 HH07AT171
— HH07AT175
— HH07AT175
HH93AZ175
HH93AZ173
HH93AZ186 or
HH93AZ195
HH93AZ183 or
HH93AZ196
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.
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.
The LEDs are not field replaceable.
Manual
changeover in
cooling
Auto
changeover in
cooling
Manual
changeover in
cooling
Auto
changeover in
heating
Copyright © 1995 Honeywell Inc. • • All Rights Reserved
X-XX UL
69-0920
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.
If this control is replacing a control that contains
mercury in a sealed tube, do not place your old
control in the trash.
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.
INSTALLATION
When Installing this Product…
Read these instructions carefully. Failure to follow
them could damage the product or cause a hazardous condition.
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.
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
Thermostats are calibrated at the factory by using
subbases mounted at true level. Inaccurate subbase leveling will cause thermostat control
deviation.
Location
Install the thermostat about 5 ft (1.5m) above the floor in
an area with good air circulation at average room
temperatures.
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.
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.
Mount the subbase on a wall or horizontal outlet box. To
mount it on a vertical outlet box, order Honeywell part no.
196393A Cover Plate Assembly, which includes an
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.
Pull about 6 in. (152 mm) of wire through the hole.
IMPORTANT
Use 18 gauge, color-coded thermostat cable for
proper wiring.
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.
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.
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.
NOTE: The cover is hinged at the top and must be
removed by pulling out at the bottom.
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.
69-0920
2
Y594 (MULTISTAGE THERMOSTAT SUBBASE) PACKAGE
VERTICAL
OUTLET
BOX
1
HORIZONTAL
OUTLET
BOX
SUBBASE
SUBBASE
MOUNTING SCREWS (2)
CAPTIVE
MOUNTING SCREWS (2)
1 NOT INCLUDED WITH UNIT.
2 ACCESSORY PARTS AVAILABLE (193121A).
Fig. 1. Installation of subbases and thermostat on
SPIRIT LEVEL
TOP
MOUNTING
HOLES (2)
outlet box.
1
6
0
5
T
A
E
H
WIRING
TERMINAL
MOUNTING
SCREWS (2)
ADAPTER
RING
0
8
0
7
0
2
THERMOSTAT
L
O
THERMOSTAT
O
C
0
8
0
COVER
7
0
0 6
5
50 60 70 80
THERMOSTAT
CABLE OPENING
COVER
PLATE
Note the tabs along the top inside edge of the
thermostat base. The tabs fit into the subbase
2
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.
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:
Remove thermostat from the subbase. Make sure
the power is on.
Connect an ac ammeter of appropriate range
between the heating terminals of the subbase:
Stage 2: between W2 and R.
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
M6009
set the adjustable heat anticipator(s) to match the
reading(s) measured in step 4. See Fig. 8.
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.
MOUNTING
HOLES (2)
FOR STRAIGHT
INSERTION–
STRIP 5/16 in. (8 mm)
SUBBASE TERMINAL SCREW
POST (2) FOR
MOUNTING
THERMOSTAT
Fig. 2. Leveling the subbase.
FOR WRAPAROUND–
STRIP 7/16 in. (11 mm)
BARRIER
Fig. 3. Wiring connections.
TO SPRING FINGER
CONTACTS ON THE
THERMOSTAT
(UP TO 12)
M927
M928
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.
ON: Thermostat automatically switches between heat
and cool modes, depending on the indoor temperature.
SUPL. HT.: Supplemental heat is energized. Cooling
system is off. Compressor cannot operate.
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.
3
69-0920
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