Honeywell T8624D User Manual

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INSTALLATION INSTRUCTIONS

69-1412-1

T8624D Chronotherm

Deluxe Programmable

Multistage Thermostats

APPLICATION

The T8624D Chronotherm® IV Deluxe Programmable

Multistage Thermostats provides electronic control of 24

Vac single-zone multistage systems.

Refer to Table 1 for a general description of the

thermostats. All T8624 thermostats require a common

wire to supply power.

Table 1. Description of T8624 Thermostats.

MERCURY NOTICE

If this control is replacing a control that contains

mercury in a sealed tube, do not place your old

control in the trash. Dispose of properly.

Contact your local waste management authority

for instructions regarding recycling and the

proper disposal of the old control.

INSTALLATION

When Installing this Product...

1. Read these instructions carefully. Failure to follow

the instructions can 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 completing installation, use these instructions

to check out the product operation.

Location

Install the thermostat about 1.5m (5 ft) above the floor in

an area with good air circulation at average temperature.

See Fig. 1.

Do not install 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 sun or appliances.

— concealed pipes and chimneys.

— unheated (uncooled) areas such as an outside wall

behind the thermostat.

T8624 Changeover System Selection

Fan

Selection Comments

D Automatic Heat-Off-Cool-Auto On-Auto System and fan selections are done by keyboard.

Questions and Answers:

S
Stephanie MoralesAug 12, 2025
Why is my Honeywell T8624D heating not working?
- S
  shannon56Aug 12, 2025
  Your Honeywell Thermostat might not be heating because of several reasons: * There may be no power to the thermostat. Check for 24 Vac between R and W terminals. If there's no 24 Vac, check the circuit breaker (reset if tripped), the system fuse (replace if blown), the HVAC equipment power switch (set to On), and the wiring between the thermostat and HVAC equipment (replace broken wires and tighten loose connections). If 24 Vac is present, continue troubleshooting. * The thermostat's minimum off time might be activated. Wait up to five minutes for the system to respond. * The system selection might not be set to Heat. Ensure the system selection is set to Heat. * The heating setpoint might be below room temperature. Check the heating setpoint and set it to the desired temperature.