Honeywell CT70 User manual
1
CT70
Heat Pump
Thermostat Wiring Guide
2
3
HOW TO USE THIS GUIDE
Before you disconnect the wires and remove your
existing thermostat, be sure this new thermostat, see the
CT70 wiring hookup diagram, will replace it and that you
understand how you will reconnect the wiring. To do that,
proceed as follows:
Step 1
Find the manufacturer of your heat pump in the Table of
Contents, and turn to the appropriate page.
Step 2
Expose the wiring on your existing thermostat (the
subbase) and check that the terminals on your existing
thermostat coincide with the terminals shown in the
second column (Existing thermostat wiring).
If they do, read and follow the installation instructions
provided with the thermostat.
If they do not, call Honeywell Customer Assistance toll
free at 1-800-468-1502, Monday-Friday, 7:00 a.m. - 5:30
p.m. Central time, to be sure you can safely use this
thermostat to control your heat pump.
Before you call, please have the following information
available: thermostat model number and date code, heat
pump model number and manufacturer, and number of
wires connected to the thermostat. The date code is
usually stamped on the back of the thermostat and is a
four-digit number; for example, 9346.
4
5
TABLE OF CONTENTS
How to Use This Guide ................................................. 3
Heat Pumps are Different .............................................. 6
Heat Pumps are Two Systems in One .......................... 7
Definitions of Terminal Functions ............................... 8,9
Heat Pump Manufacturers ..................................... 11-22
Amana....................................................................11
American Standard................................................ 20
Arcoaire................................................................. 13
Bard....................................................................... 12
Borg Warner ..................................................... 21,22
B.D.P. (Bryant-Day/Night-Payne) .......................... 14
Carrier ................................................................... 15
Comfortmaker ....................................................... 13
Friedrich ................................................................ 16
Heil Quaker ........................................................... 17
Janitrol................................................................... 12
Lennox .................................................................. 18
Luxaire (Moncrief, Fraser, Johnston) .................... 21
Rheem................................................................... 19
Ruud...................................................................... 19
Snyder General ..................................................... 13
Tappan .................................................................. 12
Tempstar ............................................................... 17
Trane..................................................................... 20
Whirlpool ............................................................... 17
Williamson............................................................. 12
York .................................................................. 21,22
6
HEAT PUMPS ARE DIFFERENT
Heat pump systems
usually have a
supplemental,
Second Stage
heating system that
operates only when
necessary. This
heat pump
thermostat is
designed to
minimize more
expensive second-
stage operation,
indicated by the
green AUX. HEAT
light on your
thermostat.
7
HEAT PUMPS ARE TWO SYSTEMS IN ONE
In mild weather, virtually all of the demand for heat in
buildings can be met by the heat pump compressor.
This
First Stage process of moving heat indoors is very
economical. As the air becomes colder outside, the first
stage may be unable to deliver enough heat to maintain the
desired comfort level in the building.
During high heat demand, the thermostat will call for
additional Second Stage power from the auxiliary heat
system.
This auxiliary heat is commonly electric resistance
heat and is two to three times more expensive to operate
than the compressor. If you have specific questions
concerning the operation of your heat pump, please contact
the equipment manufacturer.
INDOOR
AIR
OUTDOOR
AIR
HEAT
TRANSFER
AUXILIARY
HEATING
ELEMENT
OFF
OUTDOORS
MILD WEATHER
INDOORS
M9069
INDOOR
AIR
OUTDOOR
AIR
HEAT
TRANSFER
AUXILIARY
HEATING
ELEMENT
ON
OUTDOORS
SEVERE WEATHER
INDOORS
M9078
8
DEFINITIONS OF TERMINAL FUNCTIONS
Each terminal of the CT70 controls a different heat pump
function. Here is a list of the possible heat pump
functions:
Function Definition
FIRST STG. HEAT:
When this terminal is activated, the heat
pump is on and heating the living space.
AUXILIARY HEAT:
When this terminal is activated, the
auxiliary heating source is on because the
heat pump is unable to meet the heating
demand of the living space.
FIRST STG. COOL:
When this terminal is activated, the heat
pump is on and cooling the living space.
COMPRESSOR:
When this terminal is activated, the heat
pump is on and either heating or cooling
the living space, depending on the system
switch position.
C/O VALVE HEAT:
Heating Changeover Valve. This terminal
is activated when the system switch is in
the HEAT position. It provides changeover
in heat pumps that change over in
heating.
C/O VALVE COOL:
Cooling Changeover Valve. This terminal
is activated when the system switch is in
the COOL position. It provides
changeover in heat pumps that change
over in cooling.
EM. HEAT:
Emergency Heat. This terminal is
activated when the system switch is in the
EM. HT position. In this situation, the heat
pump is not activated.
9
FAN:
When this terminal is activated, the fan is
on. With the fan switch in the auto
position, the fan cycles on and off with the
heat pump. With the fan switch in the ON
position, the fan is
on continuously.
MULTIPLE AUX.
HEAT LOADS:
This terminal is activated when additional
auxiliary heat loads are required. Because
the CT70 only has provisions for one
auxiliary heat load, these loads must be
connected to the AUXILIARY HEAT
terminal.
OUTDOOR
SENSOR:
This terminal is not connected to the
CT70. On your original thermostat, this
terminal was activated by an outdoor
sensor that controlled the auxiliary heat
source.
OUTDOOR STAT:
Outdoor Thermostat. This terminal is
activated when the system switch is in the
EM. HT. position. The outdoor thermostat
controls the amount of auxiliary heat that
is activated.
POWER:
This terminal connects to the power side
of the 24-volt transformer.
COMMON:
This terminal connects to the common
side of the 24-volt transformer.
SYSTEM MONITOR:
Some heat pumps have the ability to
indicate when the heat pump is
malfunctioning. When this occurs, this
terminal is activated and the EM. HT. LED
is activated.
10
Typical wiring hookup of CT70 with jumper intact.
M8504
W2
W1
X
O
E
GY1
R
LB
L1
(HOT) L2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
REMOVE W1-Y1 JUMPER WHEN HEAT RELAY 1 IS USED.
WHEN L TERMINAL IS CONNECTED TO SYSTEM MONITOR, EM. HEAT. LED
ALSO INDICATES COMPRESSOR MALFUNCTION.
X TERMINAL MUST BE CONNECTED FOR PROPER OPERATION.
1
2
3
4
COMPRESSOR
CONTACTOR
FAN RELAY
EM. HEAT
RELAY
CHANGEOVER
RELAY (HEAT)
HEAT RELAY 1
CHANGEOVER
RELAY (COOL)
AUX. HEAT
RELAY
SYSTEM
MONITOR
2
3
4
Table of contents
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