Honeywell T87F Universal Thermostat

Application

The T87F Universal Thermostat provides temperature control for 24 to 30 Vac residential heating, cooling, or heating/cooling systems. For heating systems, it mounts on the provided wallplate. For cooling-only or heating/cooling systems, use the 137421A (or 198170A for textured designer model) Heating-Cooling Wallplate with remote switching, or the Q539 Subbase for switching at the thermostat location.

The single-pole, double-throw (spdt) switch makes one set of contacts on a temperature fall to operate the heating system. The other set of contacts makes on a temperature rise to operate the cooling system when the T87F controls cooling.

Models with a positive Off feature break the electrical circuit to prevent system operation when the switch is moved to the Off position. These models require the 137421B Wallplate for cooling or heating/cooling systems.

Heat anticipation is adjustable from 0.1 to 1.2 Amperes.

Mercury Notice

If replacing a control containing mercury in a sealed tube, do not discard the old control in the trash. Contact your local waste management authority for recycling and proper disposal instructions.

Installation and Setting

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 and in the instructions to ensure suitability for your application.
3. Installation should be performed by a trained, experienced service technician.
4. After installation, verify product operation as described in these instructions.

Important Notes

The T87F is carefully adjusted at the factory. Handle the thermostat with care to maintain accuracy.

Cautions

• Electrical Hazard: Disconnect power supply before beginning installation to prevent electrical shock, personal injury, or equipment damage.
• Equipment Damage Hazard: Do not short across relay coil terminals, as this can burn out the heat anticipator.

Location

Select a location approximately 1.5 m (5 ft) above the floor in an area with good air circulation and average temperature. Avoid mounting the thermostat where it can 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 or uncooled areas behind the thermostat.

Mounting Subbase Wallplate (Fig. 2)

• Use a spirit level to accurately level the wallplate or subbase. Inaccurate leveling can cause thermostat control deviation.
• When using the T87F with a Q539 Subbase, follow the specific mounting and wiring instructions provided with the subbase.
• Place the wallplate on the wall at the desired location. Pull the thermostat cable through the entrance hole.
• Fasten the wallplate, but do not fully tighten the screws initially.
• Level the wallplate using a spirit level (see Fig. 1) and then tighten the screws.
• After wiring the wallplate, plug the cable entrance hole to prevent drafts from affecting the thermostat.

Note: To mount the T87 Thermostat on an outlet box, order the 129044A Adapter Ring Assembly.

Wiring

All wiring must comply with local electrical codes and ordinances.

Caution

Electrical Hazard: Disconnect power supply before beginning installation to prevent electrical shock, personal injury, or equipment damage.

The T87F is adaptable to most 2-wire, 24 to 30 volt heating systems and most 3-wire, 24 to 30 volt heating systems controlled with a Series 10 Thermostat.

Refer to Figures 3-7 for typical application hookups. For cooling control, consult the hookups in the Q539 Subbase instructions. For system variations, refer to the installation instructions for the controlled equipment.

Mounting Thermostat to Wallplate or Subbase

• To remove the standard cover, pull the ring outward with fingertips while lightly pressing the dial with thumbs.
• To remove a locking cover, loosen the three screws on the cover edge using the supplied Allen wrench and remove the cover.
• Remove and discard the plastic insert protecting the mercury switch.
• Align the thermostat over the wallplate and tighten the three captive mounting screws. These screws complete the electrical connections.
• Adjust the heat anticipator to match the current rating of the primary control (see Fig. 8).

Heat Anticipator Setting

• If the T87F is used for 3-wire, spdt, heating-only (series 20) control (Fig. 6), set the heat anticipator to 1.2 (far left of the scale). A fixed resistor heater is provided in the 137421A or 198170A Wallplate for this application.
• For other control applications, adjust the anticipator to match the current rating of the primary control, which is usually stamped on its nameplate. Move the indicator to the marking that matches this rating. The indicator can be moved with fingers or a pencil point through the hole shown in Fig. 8.
• If the current rating is not provided:
  1. Connect an AC ammeter (e.g., 0-2.0A range) between the R and W terminals on the wallplate or subbase.
  2. Allow the system to operate for one minute before reading the ammeter.
  3. Move the anticipator indicator to match the ammeter reading.

Note: A slightly higher setting may be desirable for some systems to achieve longer burner-on times (fewer cycles per hour).

Recalibration

The T87F is factory calibrated and recalibration should not typically be necessary. If the thermostat is accurately leveled but remains out of calibration, order the 104994A Calibration Wrench for instructions.

Checkout

Heating

1. Turn the temperature setting to the lowest point. If a subbase or remote switching is used, set the System switch to Heat.
2. Raise the temperature setting until the heating equipment starts.
3. Lower the temperature setting below the room temperature; the heating system should shut down.
4. Ensure all equipment responds properly to the thermostat.
5. Heating equipment should stop when the dial is turned below the room temperature.

Cooling

• Caution: Equipment Damage Hazard. Operate cooling equipment within guidelines to prevent compressor damage. Do not operate cooling when the outdoor temperature is below 10°C (50°F). Allow a five-minute off-time after the compressor has run before restarting.
• If the T87F controls cooling, set the System switch (if used) to the Cool position.
• Lower the temperature setting until the cooling equipment starts.
• Raise the setting above the room temperature; the cooling system should shut down.
• Ensure all equipment responds properly to the thermostat.