TRADELINE
The Y594 Pack provides 24 to 30 Vac control of standard
2 stage heating and 1 stage cooling systems.
The stages of heat make sequentially as the temperature
drops. Make refers to the mercury switch initiating a call
for heat or cool.
There are about 2°F (1°C) between stages so that the
second stage makes only when the first stage cannot handle
the load. This is the interstage differential.
M3375
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 in-
structions regarding recycling and the proper disposal of this
control, or of an old control containing mercury in a sealed
tube.
WHEN INSTALLING THIS PRODUCT...
1. Read these instructions carefully. Failure to follow
them could cause a hazardous condition.
2. Check the ratings given in the instructions and on
the product to make sure the product is suitable for your
application.
3. Installer must be a trained experienced service
technician.
4. After installation is complete, check out product op-
eration as provided in these instructions.
IMPORTANT: An incorrectly leveled subbase will cause
the temperature control to deviate from setpoint. It is
not a calibration problem.
®
Y594 Combination Pack
(T874 Multistage Thermostat
Installation Instructions for the Trained Service Technician.
Application
Operation
Recycling Notice
Installation
J.H. • 1-95 •
• ©Honeywell Inc. 1995 • Printed in U.S.A. • Form Number 69-0882B
M3375
and Q674 Subbase)
CAUTION
1. Disconnect power supply to prevent electrical
shock or equipment damage.
2. To prevent interference with the thermostat
linkage, keep wire length to a minimum and
run wires as close as possible to the subbase.
3. Do not overtighten thermostat captive mount-
ing screws because damage to subbase threads
can result.
4. Do not short across coil terminals on relay. This
can burn out the thermostat heat anticipator.
LOCATION
Install the thermostat about 5 ft (1.5m) above the floor in
an area with good air circulation at average temperature.
Do not install the thermostat where it may be affected by:
— drafts, or dead spots behind doors and in corners.
— hot or cold air from ducts.
— radiant heat from sun or appliances.
— concealed pipes and chimneys.
— unheated (uncooled) areas such as an outside wall
behind the thermostat.
MOUNT SUBBASE
The thermostat subbase can be mounted on a vertical
outlet box, horizontal outlet box or directly on the wall.
1. If you must mount the subbase on a vertical outlet
box, order Honeywell part no. 193121A Adapter Assembly.
See Fig. 1. The assembly includes an adapter ring, two
screws and a cover plate to cover marks on the wall. Install
the ring and cover plate on the vertical outlet box.
For a wall installation, hold subbase in position and mark
holes for anchors. See Fig. 2. Wall anchors must be obtained
from local hardware store. Be careful that the wires do not
fall back into the wall opening. Set aside subbase. Drill four
3/16 in. (4.6 mm) holes and gently tap anchors into the holes
until flush with the wall.
2. Pull electrical wires through the cover plate (if used)
and subbase cable opening. See Fig. 3.
3. Secure the cover plate (if used) and subbase with the
screws provided. Do not fully tighten the subbase screws.
4. Level the subbase using a spirit level. See Fig. 3, and
firmly tighten subbase mounting screws. The subbase mount-
ing holes provide for minor out-of-level adjustments.
IMPORTANT: An incorrectly leveled subbase will cause
the temperature control to deviate from setpoint. It is
not a calibration problem.
1
69-0882B