Honeywell T841A,B Easy-To-SeeTM Heat Pump Thermostat Instruction Manual
- June 17, 2024
- Honeywell
Table of Contents
Honeywell T841A,B Easy-To-SeeTM Heat Pump Thermostat
Product Information
Specifications
- Product Name: T841A,B Easy-To-SeeTM Heat Pump Thermostat
- Control : 24 Vac
- Heating Stages: 2-stage
- Cooling Stages : 1-stage
- System Switching (T841A): EM. HT.-HEAT-OFF-COOL
- System Switching (T841B): HEAT-OFF-COOL
- Fan Switching: AUTO-ON
- Temperature Setting : Easy touch or sight with raised numbers
- Temperature Setpoint Lever : Indents every two degrees
- Wallplate : Features raised letters for system and fan switch settings
- Test Holes : Provided on the front for test meter probes
- LED Indicators (T841A only): AUX. HT. (green or amber) for auxiliary heat, EM. HT. (red) for emergency heat
- MERCURY NOTICE : Contains mercury in a sealed tube, proper disposal required
Product Usage Instructions
Installation Instructions
- Read the instructions carefully before installation.
- Check the ratings on the product to ensure suitability for your application.
- Only trained and experienced technicians should perform the installation.
- Disconnect power before beginning installation to prevent electrical hazards.
- To prevent interference with the thermostat linkage, keep wire length to a minimum and run wires as close as possible to the thermostat base.
- Do not short across coil terminals on the relay to avoid damaging the thermostat heat anticipator.
- Never install more than one wire per terminal unless a factory-supplied jumper with a spade terminal is used.
Operation
The T841A,B Easy-to-SeeTM Heat Pump Thermostat is designed to control 2-stage heating and 1-stage cooling in heat pump systems with manual changeover.
For the T841A Thermostat (not applicable to T841B Thermostat), LED indicators light up to indicate specific system conditions:
- AUX. HT. LED (green or amber) lights up when auxiliary heat (second stage heat) is operating due to extremely cold weather.
- EM. HT. LED (red) lights up when emergency heat (electric strip heaters) is operating because the homeowner physically switched to EM. HT. position.
Test Holes
Test holes are provided on the front of the thermostat for accommodating test meter probes without removing the thermostat from the wall. Remove the thermostat cover to expose the labeled test holes corresponding to the terminals on the thermostat back.
FAQ
- Q: What should I do with the control containing mercury in a sealed tube?
- A : Do not place the control in the trash. Contact your local waste management authority for instructions on recycling and proper disposal.
- Q: Can I install multiple wires per terminal?
- A : No, never install more than one wire per terminal unless a factory-supplied jumper with a spade terminal is used.
APPLICATION
The T841A, B Easy-to-See™ Heat Pump Thermostat provides 24 Vac control of
2-stage heating and 1-stage cooling in heat pump systems, using manual change-
over.
The T841A Thermostat provides EM. HT.-HEAT-OFF-COOL System switching and AUTO-
ON Fan switching. The T841B Thermostat provides HEAT-OFF-COOL System switching
and AUTO-ON Fan switching.
The side of the thermostat features raised numbers for easy temperature
setting by touch or sight. An audible click is heard with indents every two
degrees as the temperature setpoint lever is moved. The thermostat wallplate
features raised letters to aid in setting the System switch and Fan switch
settings. See Fig. 1.
The T841A,B include a thermostat and wallplate.
Test holes are provided on the front of the thermostat to accommodate test meter probes without removing the thermostat from the wall. Remove the cover of the thermostat to expose the test holes that are labeled to correspond with the terminals on the thermostat back.
OPERATION
The stages of heat occur sequentially as the temperature drops. Make refers to
the mercury switch initiating a call for heat or cool.
There is about 1°F (0.6°C) between stages so the second stage (auxiliary heat)
makes only when the first stage cannot handle the load. This °F is the
interstage differential. For T841A Thermostat only (not for T841B Thermostat):
light emitting diode (LED) indicators light when something specific happens
within the system:
When AUX. HT. green or amber LED lights, auxiliary heat (second stage heat) is operating because the weather is so cold, the heat pump alone cannot handle the load.
When red EM. HT. LED lights, emergency heat is operating (electric strip heaters), because home-owner physically switched to EM. HT. position. See heating/cooling manufacturer instructions.
INSTALLATION INSTRUCTIONS
MERCURY NOTICE
This control contains mercury in a sealed tube. Do not place the 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.
Contract 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 hazard-ous 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 technician.
- After installation is complete, check out product operation as provided in these instructions.
CAUTION
- Electrical Hazard.
- Can cause Disconnect electrical shock or equipment damage.
- Disconnect power before beginning installation.
IMPORTANT
-
* To prevent interference with the thermostat linkage, keep wire length to a minimum and run wires as close as possible to the thermostat base.-
Do not short across coil terminals on the relay.
This can burn out the thermostat heat anticipator. -
Never install more than one wire per terminal unless a factory-supplied jumper with a spade terminal is used.
-
HEAT PUMP THERMOSTAT
Location
Locate the thermostat between 4 ft (1.2m) and 5 ft (1.5m) above the floor in
an area with good air circulation at average room temperature.
NOTE : Because of the height restrictions of some disabled users, it may
be necessary to lower the thermostat location to 4 ft (1.2m) above the floor.
-
Do not install a 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, appliances or fireplaces.
-
concealed pipes and chimneys.
-
unheated (uncooled) areas such as an outside wall behind the thermostat.
-
This thermostat is a precision instrument and was carefully adjusted at the factory. Handle it carefully.
Mounting -
The T841A,B can be mounted directly on a wall or a horizontal outlet box. Choose the method that best fits your installation. In replacement applications, check the existing thermostat wires for cracked or frayed insulation. Replace any wires in poor condition.
To remove the thermostat cover:
- Grasp the thermostat cover at the top and bottom with one hand.
- Pull outward on the bottom edge of the cover until it snaps free of the thermostat base.
- Carefully remove and save the packing material surrounding the mercury switches.
Wiring
All wiring must comply with local codes and ordinances. Follow equipment
manufacturer wiring instructions when available.
NOTE : Four screws are provided with the thermostat; only two are
required for mounting.
- Run wiring (if necessary) to the location. If wiring is plastered into the wall, make a hole next to the wire and loosen the wires so they can be pushed back into the wall later.
- Thread the wires through the hole.
- Pull the wires through the entrance hole on the wallplate.
- Connect the wires to the terminals on the back of the thermostat. See Fig. 1-3.
- Push the excess wire back through the hole and plug any openings with packing material to prevent drafts that can affect thermostat performance.
- Use two of the four screws provided to loosely secure the thermostat and the wallplate to the wall or outlet box through the two middle mounting holes. See Fig. 1.
- NOTE : The sheet metal screws included with the thermostat are designed for use in plaster walls that do not need anchors.
- IMPORTANT
- An incorrectly leveled thermostat causes inaccurate temperature control.
- Exactly level the thermostat using a spirit level or plumb line.
- Tighten the screws in the middle mounting holes.
- Replace the thermostat cover.
SETTINGS
Temperature Setting
The enlarged, raised numbers on the right edge of the thermostat can be used
for easy temperature setting by touch or sight while moving the temperature
setpoint lever to the desired temperature setting. The large 5, 6, 7 and 8
refer to 50°F (10°C), 60°F (16°C), 70°F (21°C) and 80°F (27°C), respectively.
A click is heard with indents every two degrees as the temperature setpoint
lever is moved. See Fig. 1.
System Switch Setting
The enlarged, raised letters on the left bottom edge of the wall plate can be used for easy recognition of System switch settings:
For the T841A Thermostat: The large EH, H, O, and C refer to EM. HT., HEAT,
OFF, and COOL.
For the T841B Thermostat: The large H, O and C refer to EM. HT., HEAT, OFF,
and COOL.
The System switch settings control the system operation as follows:
EM.HT (only on T841A): Emergency heat relay is energized. The cooling system
is off. The compressor is de-energized.
The fan runs on call for heat if the Fan switch is in the AUTO position. EM. HT. LED is on.
HEAT : The heating system is automatically controlled by the thermostat.
The cooling system is off.
OFF : Both the heating and cooling systems are off. If the fan is set to
the AUTO position, the cooling fan is also off.
COOL : The cooling system is automatically controlled by the thermostat.
The heating system is off.
Fan Switch Setting
On the T841A,B, large A, O raised letters on the right bottom edge of the wallplate refer to AUTO and ON fan settings. The Fan switch settings control the fan as follows:
AUTO : Fan operates in response to thermostat in both heating and
cooling.
ON : Fan operates continuously.
CHECKOUT
Heating
Move the System switch on the thermostat to HEAT and the Fan switch to AUTO.
Move the temperature setpoint lever to about 10°F (6°C) above the room
temperature. The heating should start and the fan should run. Move the
setpoint lever about 10°F (6°C) below the room temperature. The heating and
fan should shut off.
IMPORTANT
To prevent compressor short cycling, a mini-mum-off timer can be included to prevent the compressor from starting for up to five minutes from when the thermostat last turned off the compressor, or from when the system first received power.
Cooling
CAUTION
- Compressor Damage Hazard.
- Operating cooling equipment in cold weather can damage the compressor.
- Do not operate the air conditioner if the outdoor temperature is below 50°F (10°C).
Move the System switch on the thermostat to COOL and the Fan switch to AUTO.
Move the temperature setpoint lever about 10°F (6°C) below the room
temperature. Cooling and fan should start (see Note in Checkout section). Move
the setpoint lever about 10°F (6°C) above the room temperature. Cooling and
fan should shut off.
Fan
Move the System switch to OFF, and the Fan switch to ON. The fan should run continuously. Move Fan switch to AUTO. In this position, the fan operates in response to the thermostat in both heating and cooling.
Automation and Control Solutions
Honeywell International Inc.
1985 Douglas Drive North 35 Dynamic Drive
Golden Valley, MN 55422
Printed in U.S.A. on recycled paper containing at least 10% post-consumer paper fibers.
References
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