Honeywell Y594 Multistage Thermostat Installation Instruction

Honeywell Y594 Multistage Thermostat 

APPLICATION

Thesethermostats and subbases provide 24 to 30 Vac control for two-stage heating and one-stage cooling heat pump systems as follows:

MODEL	CHANGEOVER	SYSTEM SWITCHING	FAN SWITCHING
Y594G (T874G/Q674F)	Automatic (Heat or Cool)	OFF-EM.HT.-HEAT- AUTO-COOL	AUTO-ON
T874R/Q674L	Manual	EM.HT.-HEAT-OFF-COOL	AUTO-ON

OPERATION

On a two-heat thermostat, the two stages of heat  “make” sequentially as the temperature drops. “Make” refers to the mercury switch initiating a call for heat or COOL There is about 2 F [1 .I C] between stages so that the second stage (auxiliary heat) makes only when the first stage can’t handle the load. This is the interstage differential. Three LEDs (light-emitting diodes) are included on the sub-base. The red CHECK LED lights when something needs to be checked or done to maintain the efficient operation of the system. See your heating system instructions to find out specifically what the CHECK LED signifies. The green LED lights when the AUX. HT. stage (second stage) heat is operating. The red EM.HT. LED lights when the EM.HT. relay is energized, usually operating electric strip heaters.

INSTALLATION

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 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

MOUNTING THE SUB BASE
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, or box, order 19312lA Adapter Assembly (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

CAUTION

1. Disconnect the power supply to prevent electrical shock or equipment damage.
2. Run wires as close to the subbase as possible. To prevent interference with the thermostat linkage, keep wire length to a minimum. Push excess wire back into the hole, and plug the hole to prevent drafts from affecting thermostat operation.
3. Do not overtighten thermostat captive mounting screws as damage to subbase threads may result.
4. Do not short across coil terminals on the relay. This may burn out the heat anticipator.

LOCATION
Install the thermostat about above the floor in an area with good circulation at an 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 the sun or appliances.
• concealed pipes and chimneys.
• unheated (uncooled) areas behind the thermostat, such as an outside wall.

For a wall installation, hold the subbase in position and mark holes for anchors (Fig. 2). Wall anchors must be obtained from the local hardware store. Take care that the wires do not fall back into the wall opening. Set subbase aside. Drill four 3116 in. [4.8 mm] holes and gently tap anchors into the holes until flush with the wall.

Pull wires through the cover plate (if used) and subbase cable opening (Fig. 3). Secure the cover plate (if used) and subbase with the screws provided. Do not fully tighten the subbase screws.

Fig. 4-Internal schematic and typical hookup of T874G and Q674F in the heat pump system

 

Fig. 5-Internal schematic and typical hookup of T8?4R and Q674L in the heat pump system

Level the subbase using a spirit level, as shown in Fig. 3, and firmly tighten the subbase mounting screws. The subbase mounting holes provide for minor out-of-lever adjustments.

WIRING THE SUBBASE
All wiring must comply with local electrical codes and ordinances. Follow the equipment manufacturer’s wiring instructions when available. To wire the subbase, proceed as follows:

1. Connect system wires to the subbase as shown in Fig.4orSAlettercode is near each terminal for identification. The terminal barrier permits straight or conventional wraparound wiring connections (Fig. 6)..
2. Firmly tighten each terminal screw.
3.  Fit wires as close to the subbase as possible. Push excess wire back into hole.
4. Plug hole with nonflammable insulation to prevent drafts from affecting the thermostat.
5. Note the tabs along the top inside edge of the thermostat base. The tabs fit into corresponding slots on top of the subbase. Mount the thermostat on the subbase.
6. Align the two captive mounting screws in the thermostat base with the oosts on the subbase fFia. 7). Tighten both screws. DO NOT OVERTIGHTEN SCREWS or damage to subbase posts may result.

MOUNTING THE THERMOSTAT

1. Remove the thermostat cover by pulling the bottom edge of the cover upward until it snaps free of the retaining posts.
   NOTE: The covar is hinged at the top and must be removed by pulling up at the bonom.
2. Carefully remove and discard the polystyrene packing insert which protects the mercury switches during shipment.
3. Turn the thermostat base over and note the spring fingers which engage the subbase contacts. Make sure the spring fingers are NOT bent flat, preventing proper electrical contact with the subbase.

TEMPERATURE SETTING COOL
cooling system is controlled by the thermo-On the T874G, move the heating and cooling set point stat. Heating system is off. levers to the desired positions. The minimum differential AUTO (T874G only)-thermostat automatically between heating and cooling set points is 3 F [1.7 C]. On changes between heaat nd cool modes, depending the T874R one lever controls both heating and cooling. upon the indoor temperature.

SUBBASE SETTING
System switching positions control thermostat operation as follows: EM. HT.-emergency heating system is energized. Red EM. HT. LED on subbase is on. Cooling system is off. HEAT-heating system is controlled by the thermostat. Cooling system is off. OFF-both the heating and cooling systems are off. Fan switching positions control fan operation as follows: ON-fan operates continuously. AUTO-fan operates with equipment as controlled by the thermostat. To switch positions, usethumband indexfingertoslide lever to desired position. Switch lever must stop in detent directly over desired function indicator mark for proper circuit operation.

CHECKOUT

HEATING
Move the system switch on the subbase to HEAT and the fan switch to AUTO. Move the heating set point lever on the thermostat about 10 F [56 C] above room temperature. Heating should start, providing there is no time delay or outdoortemperature limiting system, and the fan should run after a short delay. Move the heating set point lever about 10 F [56 C] below room temperature. The heating equipmentshould shutoff, and the fan should run for a short time, then shut off. Move the system switch on the subbase to COOL. Move the cooling set point lever on the thermostat about 10 F [56 C] below room temperature. The cooling equipment and fan should start. Move the cooling set point lever about 10 F [5.6 C] above room temperature. The cooling equipment and fan should stop.
NOTE: On the T874R, the same lever controls both heating and cooling.

FAN
Move the subbase system switch to OFF, and the fan switch to ON. Thefa n should run continuously. When the is in the AUTO position, fan operation is controlled by the heating or cooling system

THERMOSTAT

These thermostats are accurately calibrated at the factory. THEY DO NOT HAVE PROVISION FOR FIELD CALIBRATION. THERMOMETER The thermometer in your thermostat has been accurately calibrated at the factory. The thermometer should only need adjustment if it has been dropped or shifted due to mishandling. If set point lever and the thermometer reading do not agree, follow the procedure below.

1. Remove thermostat cover by pulling up from the bottom of cover until it clears the retaining posts.
2. Set the cover on a table near an accurate thermometer.
3. After allowing 5 or IO minutes for stabilization, comparethereadings.lftheyarethe same, replacecover and put system into operation. If they are different,\ recalibrate the thermostat thermometer, step 4.
4. Insert a small screwdriver in the thermometer shaft (Fig. 8) and turn it until the thermometers read the same. When the thermometer is calibrated, replace cover and place system into operation.
   NOTE: Hand heat will offset the thermometer reading. Afterm aking each adjustment, wait5 or 10 minutes for the thermometer to stabilize before comparing.

Honeywell Inc.
1885 Douglas Drive N.
Golden Valley, MN 55422-4386
international sales offices in all principal cities of the world. Manufacturing in Australia, Canada, Finland,
France, Germany, Japan, Mexico, Netherlands, Spain, Taiwan, United Kingdom, U.S.A
PRINTED IN U.SA

Honeywell Y594 Multistage Thermostat Installation Instruction

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