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T874
Honeywell T874 Product Data
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T874 MULTISTAGE THERMOST
ATS AND Q674 SUBBASES
143
60-2485—8
Fig. 123. Schematic and hookup of T874
R wit
h Q674L. Used in heat
pump applications
.
H2
FALL
H1
FALL
C1
L1
(HOT)
L2
1
2
2
1
2
POWER SUPPLY. PROVIDE
DISCONNECT MEANS AND
OVERLOAD PROTECTION
AS REQUIRED.
CONNECT CHANGEOVER
RELAY TO B FOR HEAT
CHANGEOVER, TO O FOR
COOL CHANGEOVER.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
LACO
CHP
ODT 1
RTD 1
EHR 1
RTD 2
ODT 2
EHR 2
RTD 3
COMPRESSOR
MONITOR
R
L
X
W2
G
O
E
Y
B
HEAT
CHANGEOVER VALVE
COMPRESSOR
CONTACTOR
EM. HT. RELAY
COOL
CHANGEOVER VALVE
FAN RELAY
RTD 1
RD
10
8
H2
ANTICIPATOR
6
5
4
3
2
H1/C1
ANTICIAPTOR
FAN
SWITCH
AUTO
ON
SYSTEM
SWITCH
EM. HT.
HEAT
OFF
COOL
EM. HT.
LED (RED)
AUX. HT.
LED
(GREEN)
M1030
A
142
144
Table of Contents
Table of Contents
1
Application
1
Features
1
Specifications
2
Ordering Information
2
Standard Models
3
T874 Thermostat Accessories
4
T874 Thermostat Specifications
4
Q674 Subbase Specifications
5
Heating, Cooling Levers and System LED Indicators
6
Optional Specifications (Q674 Only)
6
Location
7
Mount Subbase
7
Caution/Mercury Notice
7
Installation
7
Wire Subbase
8
Installing Q674 Subbase on Wall
8
Subbase Components and Leveling Procedure
8
Terminal Designations
9
Range Limiting and Lever Locking Methods
10
Outdoor Disconnect
10
Install and Adjust Stop Brackets
10
Mount Thermostat
11
Set the Heat Anticipator
11
Installation of Locking Cover Assembly
11
Settings
11
Temperature Setting
12
Subbase Setting
12
Setting the Adjustable Differential
12
Adjustable Heat Anticipator Scales - Diagram
12
Set Adjustable Insterstage Differential
13
Verity the Adjustment
13
Checkout
13
Fan/Outdoor Reset Thermistor
14
Thermometer
14
Calibration
14
Understanding Circuits
14
Tracing Method
15
Key to Hookup Symbols
15
Internal Schematic and Typical Hookup of a T874R Thermostat and Q674L Subbase in a Heat Pump Application
16
Tracing the Changeover Relay Circuit - Diagram
17
Tracing the Heat 1 and Anticipation Circuit - Diagram
17
Tracing the Heat 1 Ainticipation Circuit - Diagram
18
Tracing the Heat 2, Anticiapation and AUX HT LED Circuit - Diagram
18
Tracing the Emergency Heat and EM HT LED Circuit
19
Tracing the Cooling Circuit
19
Tracing the Auto Fan Circuit
20
Tracing the Fan on Circuit
20
Heat Anticipation/Cool Anticipation
21
Interstage Differential
21
Droop/Outdoor Reset
21
Operation
21
Service and Replacement of C815A Outdoor
22
Features/Led Indicators
22
Restricted Setpoint (Dod)/Applications
22
Changeover on Standard Residential Systems
22
Space Temperature Sensing Low Voltage Controls
23
Two-Stage Thermostat
23
Heat Pump Application
23
Commercial Rooftop Application
23
Cycling Rate
24
Voltage Anticipation
24
Outdoor Reset
24
Changeover
24
Low Temperature Lockouts
25
Heat Pumps with Dual Compressors
25
Two Speed Heat Pump
25
Auxiliary Heat
26
Defrost Control
26
Stage a Time Modulated Control
27
Three-Stage Thermostat
27
Emergency Heat
27
Outdoor Thermostats for Auxiliary Heat
27
Crankcase Heat
28
Compressor Fault Relay
28
T872-T874 Thermostat Cross Reference
29
Q672-Q674 Subbase Cross Reference
39
T874 Cross Reference
46
Q674 Subbase Cross Reference
71
Y594 Cross Reference
87
Schematic and Hookup of T874A, B, C, D, E, F with Q674B. Used in Standard Applications
96
Schematic and Hookup of T874C, D with Q674B. Used in Standard Applications
96
Wiring Diagrams
96
Schematic and Hookup of T874A, B, D with Q674B. Used in Standard Applications
97
Schematic and Hookup of T874R with Q674B. Used in Standard Applications
97
Schematic and Hookup of T874D with Q674B. Used in Standard Applications
98
Schematic and Hookup of T874C with Q674B. Used in Standard Applications
99
Schematic and Hookup of T874G with Q674B. Used in Standard Applications
99
Schematic and Hookup of T874W with Q674B. Used in Standard Applications
101
Schematic and Hookup of T874A, D, F with Q674D. Used in Standard Applications
102
Schematic and Hookup of T874C with Q674D. Used in Standard Applications
102
Schematic and Hookup of T874P, D, F with Q674B. Used in Pump Applications
103
Schematic and Hookup of T874G with Q674D. Used in Standard Applications
103
Schematic and Hookup of T874A with Q674Q. Used in Fan Coil Applications
104
Schematic and Hookup of T874C with Q674N. Used in Evaporative Cooler Applications
104
Schematic and Hookup of T874F with Q674B. Used in Wood/Coal Applications
105
Schematic and Hookup of T874F with Q674D. Used in Wood/Coal Applications
106
Schematic and Hookup of T874A, D, F with Q674D. Used Standard Applications
107
Schematic and Hookup of T874A with Q674B. Used in Standard Applications
107
Schematic and Hookup of T874R with Q674B. Used in Heat Pump Applications
108
Schematic and Hookup of T874P with Q674B. Used in Heat Pump Applications
108
Schematic and Hookup of T874V with Q674R. Used in Fan Coil Applications
109
Schematic and Hookup of T874C with Q674S. Used in Heat Pump Applications
109
Schematic and Hookup of T874A-D with Q674A. Used in Standard Applications
110
Schematic and Hookup of T874D, E, F with Q674R. Used in Standard Applications
110
Schematic and Hookup of T874G with Q674C. Used in Heat Pump Applications
111
Schematic and Hookup of T874H with Q674C. Used in Heat Pump Applications
111
Schematic and Hookup of T874A-D with Q674C. Used in Standard Applications
112
Schematic and Hookup of T874A with Q674C. Used in Standard Applications
112
Schematic and Hookup of T874K with Q674C. Used in Heat Pump Applications
113
Schematic and Hookup of T874P with Q674C. Used in Heat Pump Applications
113
Schematic and Hookup of T874G, H with Q674C. Used in Standard Applications
114
Schematic and Hookup of T874D with Q674E. Used in Standard Applications
114
Schematic and Hookup of T874C with Q674C. Used in Heat Pump Applications
115
Schematic and Hookup of T874A, C, D with Q674E. Used in Standard Applications
115
Schematic and Hookup of T874G with Q674C. Used in Standard Applications
116
Schematic and Hookup of T874G with Q674E. Used in Heat Pump Applications
116
Schematic and Hookup of T874A-D with Q674E. Used in Standard Applications
117
Schematic and Hookup of T874B, D with Q674E. Used in Standard Applications
118
Schematic and Hookup of T874B, D with Q674G. Used in Standard Applications
119
Schematic and Hookup of T874A-F, Q with Q674G. Used in Standard Applications
120
Schematic and Hookup of T874C, D with Q674G. Used Heat Pump Applications
120
Schematic and Hookup of T874D with Q674K. Used in Standard Applications
121
Schematic and Hookup of T874D with Q674G. Used in Standard Applications
121
Schematic and Hookup of T874F with Q674K. Used in Wood/Oil Applications
122
Schematic and Hookup of T874C with Q674G. Used in Standard Applications
122
Schematic and Hookup of T874D with Q674E. Used in Standard Applications
123
Schematic and Hookup of T874C with Q674C. Used in Standard Applications
124
Schematic and Hookup of T874W with Q674C. Used in Standard Applications
125
Schematic and Hookup of T874R with Q674L. Used in Heat Pump Applications
125
Schematic and Hookup of T874J, R with Q674L. Used in Heat Pump Applications
126
Schematic and Hookup of T874C with Q674L. Used in Heat Pump Applications
128
Schematic and Hookup of T874R, R with Q674L. Used in Heat Pump Applications
128
Schematic and Hookup of T874D with Q674L. Used in Heat Pump Applications
129
Schematic and Hookup of T874C, R with Q674L. Used in Heat Pump Applications
131
Schematic and Hookup of T874W with Q674L. Used in Heat Pump Applications
139
Schematic and Hookup of T874J with Q674L. Used in Heat Pump Applications
144
Schematic and Hookup of T874G with Q674P. Used in Heat Pump Applications
146
Schematic and Hookup of T874C, D with Q674F. Used in Standard Applications
156
Schematic and Hookup of T874G with Q674B. Used in Heat Pump Applications
157
Schematic and Hookup of T874J with Q674J. Used in Heat Pump Applications
157
Schematic and Hookup of T874G with Q674F. Used in Heat Pump Applications
158
Schematic and Hookup of T874D with Q674F. Used in Heat Pump Applications
158
Schematic and Hookup of T874H with Q674C. Used in Standard Applications
172
Schematic and Hookup of T874L with Q674C. Used in Heat Pump Applications
172
Schematic and Hookup of T874D with Q674F. Used in Standard Applications
173
Schematic and Hookup of T874N with Q674F. Used in Heat Pump Applications
182
Schematic and Hookup of T874A, D with Q674J. Used in Heat Pump Applications
183
Schematic and Hookup of T874G with Q674J. Used in Heat Pump Applications
191
Schematic and Hookup of T874L with Q674E. Used in Standard Applications
192
Schematic and Hookup of T874A with Q674E. Used in Standard Applications
199
Schematic and Hookup of T874L with Q674B. Used in Heat Pump Applications
202
Schematic and Hookup of T874S with Q674F. Used in Heat Pump Applications
207
Schematic and Hookup of T874A, D with Q674E. Used in Standard Applications
208
Schematic and Hookup of T874G with Q674G. Used in Standard Applications
210
Schematic and Hookup of T874Y with Q674F. Used in Heat Pump Applications
223
Schematic and Hookup of T874C with Q674B. Used in Heat Pump Applications
224
Other manuals for Honeywell T874
Quick Start Guide
6 pages
4
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Honeywell T874 Specifications
General
Brand
Honeywell
Model
T874
Category
Thermostat
Language
English
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