Robertshaw 8405 User manual

DIGITAL

NON-PROGRAMMABLE

THERMOSTAT

8405

ELECTRIC

GAS

OIL

NeW

1 Heat

User's Manual

Quick Start

Installation

MILLIVOLT

Application

The Robertshaw 8405 is a single-stage thermostat designed to control

24 VAC gas or electric heating or millivolt HVAC systems.

Features

• Low battery indicator

• Large backlit display

• Adjustable temperature differential: 1°F to 3.0°F (0.5°C to 1.5°C)

• Accuracy within ±1°

• Zone system compatible as a master thermostat

• Permanent memory retention

• Fahrenheit/Celsius display option

• Adjustable from 45°F to 90°F (7°C - 32°C)

• Quick wire terminal block

• Low temperature freeze protection. While in heat mode, the

thermostat will mechanically turn on the heat if the temperature

drops to 40°F (4°C) – even if the batteries are drained or missing.

110-1088B

110-1088B.qxd 3/8/05 10:28 AM Page 1

WARNING:

• Always turn off power at main fuse or circuit breaker panel before

installing, removing, cleaning, or servicing thermostat.

• Read all the information in this manual before installing this thermostat.

• DO NOT CONNECT TO 120 VAC. This is a 24 VAC low-voltage

thermostat. Do not install on voltages higher than 30 VAC.

• All wiring must conform to local and national building and electrical

codes and ordinances.

• Do not short (jumper) across terminals on the gas valve or at the

system control to test installation. This will damage the thermostat

and void the warranty.

• Do not connect ground to any terminal in this unit.

Recycling Thermostat

If this thermostat REPLACES a thermostat that contains mercury,

DO NOT discard the old thermostat in the regular trash. Mercury

is harmful to humans and the environment. For this reason, do

not open, break, or crush the mercury cell. If mercury leaks from

a damaged cell, DO NOT touch or handle mercury with bare

hands. Use protective, non-absorbent gloves to place mercury

into a sealable container. Fill the container with sand or another

absorbent material and seal the container completely.

Return the mercury or mercury products, in a sealed container, to

Invensys Controls Americas or a local recycling center for proper

disposal. If you have any questions, call Robertshaw technical

support at 1-800-445-8299.

Invensys Controls Americas

28C Leigh Fisher Blvd.

El Paso, TX 79906

Attn: Mercury Recycling Center

Step 1: Replacing Existing Thermostat

Wiring Table

Old Terminal New Label Description

M,W,Rh,R5 or 5 Rh Heat transformer, hot side

V or Rc Rc Cool transformer, hot side

H,W, or 4 W1 Heating control

F or G G Fan control relay

110-1088B.qxd 3/8/05 10:28 AM Page 2

1. Turn off power to heating system.

2. Remove cover from old thermostat to expose wires (Figure 1).

3. Disconnect wires one at a time from existing terminals. Use enclosed

labels to mark existing wires. Refer to cross references in the Wiring Table

if existing wiring does not directly match the labels.

4. Remove existing thermostat base from wall.

Step 2: Installing Model 8405 Thermostat

NOTE: FOR NEW INSTALLATIONS, MOUNT THERMOSTAT ON

INSIDE WALL, FIVE FEET ABOVE THE FLOOR. DO NOT

INSTALL BEHIND A DOOR, IN A CORNER, NEAR AIR

VENTS, IN DIRECT SUNLIGHT, OR NEAR ANY HEAT OR

STEAM GENERATING FIXTURES. INSTALLATION AT THESE

LOCATIONS WILL AFFECT THERMOSTAT OPERATION.

1. Turn power off to the heating and cooling systems.

2. Place HEAT-OFF in OFF position (Figure 2).

3. Place AUTO-ON switch into AUTO position (Figure 2).

Figure 1

heat off auto on

Figure 2

heat off auto on

110-1088B.qxd 3/8/05 10:28 AM Page 3

4. Remove the cover using a coin or screwdriver (Figure 3). Set aside.

5. Place thermostat against the wall at desired location. Make sure

wires will feed through opening (Figure 4) on base of thermostat.

6. Mark placement of mounting holes (Figure 4). Set base aside.

7. If mounting on drywall, tap plastic anchors into wall.

NOTE: Enclosed plastic anchors do not require a drilled hole

for drywall.

8. If mounting on a surface other than drywall, drill the marked holes

using a 3/16" (5mm) drill bit.

9. Align base with plastic anchors and feed wires through opening.

10. Secure base to wall with supplied screws. NOTE: The thermostat

will mount horizontally on a single gang junction box.

11. Strip end of wires 5/16” (8mm) if needed.

12. Terminal screws are already loose and ready for wire insertion.

Insert wires into terminal strip (Figure 4) matching the label to the

corresponding terminal (see Wiring Diagrams). Tighten screws.

heat off cool

hold

vac

prog

run/set hold

temp

clock

set

auto on

MON

Figure 3

GOB Y1W1

ELEC GAS

–

Figure 4

Mounting Holes

110-1088B.qxd 3/8/05 10:28 AM Page 4

Hot

Heating

Control

Transformer

24 VAC

120 VAC

HEAT ONLY

SINGLE TRANSFORMER

2-WIRE

Factory-Installed

Jumper

Hot

Heating

Control

Fan

Control

Transformer

24 VAC

120 VAC

HEAT ONLY

SINGLE TRANSFORMER

3-WIRE

Factory-Installed

Jumper

Pilot

Generator

Gas valve

250-750

SYSTEM

MILLIVOLT

Factory-Installed

Jumper

♦Wiring Diagrams

110-1088B.qxd 3/8/05 10:28 AM Page 5

13. Make sure wire connections are secure.

14. Push excess wire back through opening.

15. Set the Electric/Gas switch to either GAS for a gas/oil heating

system or ELEC for an electric/millivolt heating system (Figure 5).

16. Install two AA Energizer®brand batteries or equivalent into

battery compartment as shown (Figure 5).

17. Replace thermostat cover by snapping into place.

GOB Y1W1

ELEC GAS

–

Figure 5

TERMINAL LEGEND - 8405

TERM EQUIPMENT TO CONNECT REQ? TERMINAL FUNCTION

Rh 24VAC hot connection Yes For input of 24VAC hot

side of heat transformer

Rc 24VAC hot connection Yes For input of 24VAC hot

side of cool transformer

W1 Heat connection Yes* Energizes on a call for

heating

G Indoor fan connection Yes Energizes with Y1 & W1

terminals or with FAN

option switched to the

ON position

Correct battery

placement

ELECTRIC/GAS SWITCH

Selects fan control.

110-1088B.qxd 3/8/05 10:28 AM Page 6

Step 3: Testing the Thermostat

WARNING: DO NOT SHORT (JUMPER) ACROSS TERMINALS OF GAS

VALVE OR SYSTEM CONTROL TO TEST OPERATION. THIS WILL

DAMAGE THE THERMOSTAT AND VOID YOUR WARRANTY.

1. Put the HEAT-OFF switch into the HEAT position.

The will be displayed.

2. Press the button until the temperature setting is at least 3

degrees above room temperature. The heating system should turn

on. The fan may not turn on immediately, depending on the fan

delay built into the furnace.

3. Put the HEAT-OFF switch into the OFF position.

The heating system should turn off. The fan may

continue to run for a short period of time.

4. Put the AUTO-ON switch into the ON position.

The blower fan should turn on.

The display will show a .

5. Put the AUTO-ON switch into the AUTO

position. The blower fan should turn off.

heat off

auto on

110-1088B.qxd 3/8/05 10:28 AM Page 7

Step 4: Customizing the Thermostat

♦Settings

System

Off: The heating and cooling systems are off.

Heat: The thermostat controls the heat.

Fan

Auto: Equipment controls the fan.

On: The fan operates continuously.

♦Temperature Differential

The temperature differential is factory set at 1.0°F (.5°C). This means that

whenever the room temperature changes by one degree Fahrenheit

from the temperature setting, the system will turn on. If the system turns

on too often, increase the temperature differential.

♦Changing Fahrenheit (°F) to Celsius (°C),

the Temperature Differential, and

the Filter Monitor

1. The thermostat is preset to display the

temperature in degrees Fahrenheit (US

models) or degrees Celsius (Canadian

models). The temperature display can be

changed. Press and hold both the

and buttons for three seconds. The display will flash either an F

or C. Release buttons. Press the or button to switch the display.

2. Wait five seconds or press and the display will switch to the

differential setting.

3. The display will read diFF. The tempera-

ture differential is factory set at 1.0°F

(0.5°C). Press the or button to adjust

the differential up or down.

4. Wait five seconds or press and the

display will switch to the

filter monitor setting.

5. CHECK FILTER and the length of hours for

the filter monitor will be displayed.

6. Use the or to adjust the filter timer

from 0 (OFF) to 9900 hours. NOTE: The

filter timer is based on equipment run

time. Select the length of time based on

the recommended service interval for

your filter.

7. Press the to return to normal operation.

110-1088B.qxd 3/8/05 10:28 AM Page 8

♦Check Filter Reset

Once the filter timer has expired,

CHECK FILTER will turn on and stay

on. To clear the message and reset

the timer:

1. Press the and buttons and

hold for 3 seconds. CLr will appear

in the time display.

2. Press any key to clear the message.

The display will transition to the

temperature scale display as

described in the previous section.

3. No further input is needed. Within a few seconds, the display will

return to the normal operating mode.

♦Backlit Display

This thermostat is equipped with a backlight to make night time temper-

ature adjustments quick and easy. Press the button to activate the

backlight. The backlight will turn off after about 10 seconds of inactivity.

♦Reset

To reset the thermostat press the RESET button located above the upper

left corner of the display.

GOB Y1W1

ELEC GAS

–

RESET BUTTON

110-1088B.qxd 3/8/05 10:28 AM Page 9

Step 5: Troubleshooting

Symptom Remedy

Thermostat does not turn on system. Check wiring (see Installation

section).

Thermostat turns system on and

off too frequently.

Increase temperature differential

(see Changing the Temperature

Differential section).

Display is blank, flashing or

constant LO BATT.

Replace batteries.

System fan does not operate

properly.

Move Electric/Gas switch to

either electric or gas, to match

system (see Installation section).

Thermostat does not display

proper room temperature.

Check F/C (Fahrenheit/Celsius)

setting. See Changing Fahrenheit

(F) to Celsius (C).

Note: Although the thermostat has a low battery indicator, replace the

batteries once a year to prevent leakage and to prevent the ther-

mostat and heat/cooling system from shutting down due to lack

of battery power in the thermostat.

If problems with thermostat cannot be resolved, call:

Technical Support: (800) 445-8299

Monday-Friday 7:30 AM - 5:30 PM CST

For after hours service, a 24-hour automated help line is available.

110-1088B.qxd 3/8/05 10:28 AM Page 10

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