Robertshaw 8400 User manual

DIGITAL

NON-PROGRAMMABLE

THERMOSTAT

8400

ELECTRIC

GAS

OIL

NeW

1 Heat / 1 Cool

User's Manual

Quick Start

Installation

HEAT PUMP

Application

The Robertshaw 8400 is a single-stage thermostat designed to control

24 VAC gas or electric heating and cooling systems or single-stage

heat pump.

Features

• Low battery indicator

• Large backlit display

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

• Compressor short cycle protection

• 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.

110-1086B

110-1086B.qxd 3/8/05 10:26 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

WARNING:

In heat pump applications, do not connect anything to the W1

terminal. When switched to HP mode, W1 is connected internally

to Y1 on the 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

Y or Y6 Y1 Cooling control

H,W, or 4 W1 Heating control

F or G G Fan control relay

O O Cool active reversing valve

B B Heat active reversing valve

NOTE: ON SOME OLDER MODELS, THE C TERMINAL CAN BE EITHER THE COOLING CONTROL OR

THE COMMON SIDE OF THE TRANSFORMER. CHECK FURNACE WIRING DIAGRAM TO VERIFY

C TERMINAL. IF IT IS THE COMMON SIDE OF THE TRANSFORMER, CAP THE WIRE AND

TUCK INTO THE WALL. IF IT IS THE COOLING CONTROL, CONNECT TO THE Y TERMINAL.

110-1086B.qxd 3/8/05 10:26 AM Page 2

1. Turn off power to heating and cooling 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 8400 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-COOL in OFF position (Figure 2).

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

Figure 1

heat off cool auto on

Figure 2

heat off cool auto on

110-1086B.qxd 3/8/05 10:26 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

NON_HP HP

–

Figure 4

Mounting Holes

110-1086B.qxd 3/8/05 10:26 AM Page 4

Hot

Heating

Control

Fan

Control

Cooling

Control

Transformer T

24 VAC

120 VAC

Hot

Heating

Control

Fan

Control

Transformer

24 VAC

120 VAC

Hot

Heating

Control

Transformer

24 VAC

120 VAC

HEAT/COOL

4-WIRE

SINGLE TRANSFORMER

HEAT ONLY

2-WIRE

SINGLE TRANSFORMER

HEAT ONLY

SINGLE TRANSFORMER

3-WIRE

Factory-Installed

Jumper

Hot

Cooling

Control

Fan

Control

Transformer

24 VAC

120 VAC

COOL ONLY

3-WIRE

SINGLE TRANSFORMER

Factory-Installed

Jumper

NOTE: Remove factory

installed jumper

♦Wiring Diagrams

110-1086B.qxd 3/8/05 10:26 AM Page 5

Heating

Control

(COOLING)

Transformer

(HEATING)

Transformer

Hot

120 VAC 24 VAC

24 VAC

Hot

120 VAC

Cooling

Control

HEAT/COOL

5-WIRE

TWO TRANSFORMER NOTE: Disconnect

factory installed jumper.

Hot

Compressor

Contactor

Transformer

24 VAC

120 VAC

HEAT PUMP WITH

COOL ACTIVE

REVERSING VALVE

CAUTION: Both transformers

must be in phase or damage

may result.

to the equipment and thermostat

Hot

Transformer

24 VAC

120 VAC

HEAT PUMP WITH

HEAT ACTIVE

REVERSING VALVE

NOTE: Factory

Installed Jumper

NOTE: Factory

Installed Jumper

NOTE: Make sure the HP switch

is in the HP position.

NOTE: Make sure the HP switch

is in the HP position

When switched to HP mode,

W1 is connected internally to Y1.

Fan

Relay

Reversing

Valve

Fan

Relay

Compressor

Contactor Y1

Reversing

Valve

Fan

Relay

♦Wiring Diagrams

110-1086B.qxd 3/8/05 10:26 AM Page 6

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 heating system (Figure 5).

16. Set the HP option switch to either the HP for heat pump or

NON_HP for furnace applications (Figure 5).

17. Install two AA Energizer brand batteries or equivalent into

battery compartment as shown (Figure 5).

18. Replace thermostat cover by snapping into place.

GOB Y1W1

ELEC GAS

NON_HP HP

–

Figure 5

TERMINAL LEGEND - 8400

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

Y1 Compressor Connection Yes* Energizes on a call for

cooling

B Heat active reversing valve** No Energizes when in the

HEAT mode

O Cool active reversing valve** No Energizes when in the

COOL mode

G Indoor fan connection Yes Energizes with Y1 & W1

terminals or with FAN

option switched to the

ON position

* This thermostat can be used as a heat only or cool only thermostat. Therefore it is not always

necessary to use both Y and W.

**The O and B terminals are accessory terminals that typically are used for heat pump applications.

Correct battery

placement

ELECTRIC/GAS SWITCH

Selects fan control.

HP OPTION SWITCH

Heat pump switch.

110-1086B.qxd 3/8/05 10:26 AM Page 7

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.

CAUTION: DO NOT SWITCH SYSTEM TO COOL OR LEAVE IN COOL MODE

IF THE TEMPERATURE IS BELOW 50°F (10°C). THIS CAN

DAMAGE THE AIR CONDITIONING SYSTEM AND CAUSE

PERSONAL INJURY.

1. Place the HEAT-OFF-COOL switch into the

COOL position. The will be displayed.

2. Press the button until the temperature

setting is at least 3 degrees below the room

temperature. The air conditioning system

should turn on within a few seconds.

NOTE: ONCE THE THERMOSTAT TURNS OFF WHEN IN THE COOL MODE,

A BUILT IN 5-MINUTE DELAY PREVENTS THE SYSTEM FROM

TURNING ON AGAIN. THIS PROTECTS THE COMPRESSOR. NO

ADDITIONAL TIME DELAY RELAY IS REQUIRED. TO OVERRIDE THE

5-MINUTE DELAY FOR INSTALLATION, PRESS THE RESET BUTTON.

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

position. The air conditioning system should

turn off.

4. Put the HEAT-OFF-COOL switch into the HEAT

position. The will be displayed.

5. 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.

NOTE: If HP is selected, the heat will not come on until the 5 minute

short cycle protection has expired.

6. Put the HEAT-OFF-COOL switch into the OFF

position. The heating system should turn off.

The fan may continue to run for a short

period of time.

7. Put the AUTO-ON switch into the ON

position. The blower fan should turn on.

The display will show a .

8. Put the AUTO-ON switch into the AUTO

position. The blower fan should turn off.

heat off cool

auto on

110-1086B.qxd 3/8/05 10:26 AM Page 8

Step 4: Customizing the Thermostat

♦Settings

System

Cool: The thermostat controls the cooling.

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.

110-1086B.qxd 3/8/05 10:26 AM Page 9

♦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

NON_HP HP

–

RESET switch

110-1086B.qxd 3/8/05 10:26 AM Page 10

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