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Honeywell T874 , Fig. 97. Schematic and hookup of T874P with Q674C. Used in heat pump applications. , Fig. 98. Schematic and hookup of T874D with Q674E. Used in standard applications.

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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

123 60-2485—8

Fig. 97. Schematic and hookup of T874P with Q674C. Used in heat pump applications. Fig. 98. Schematic and hookup of T874D with Q674E. Used in standard applications.

H2

FALL

H1

RISE

CO

L1

(HOT)

L2

1

C1

RISE

COMPRESSOR CONTACTOR

FAN RELAY

CLOSED-DAY

OPEN-NITE

B RELAY

SERVICE

LED (RED)

OVERRIDE

LED (RED)

FAN

SWITCH

AUTO

ON

H1

ANTICIPATOR

SYSTEM SWITCH

JUMPER

COOL CHANGEOVER VALVE

OVERRIDE

AUTO

OFF

C1 ANTICIPATOR

1

2

3

4

5

6

8

9

10

W

P

S

X

L

B

R

C

G

Y

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED.

H2 MAKE OFFEST 8˚ F BELOW H1 MAKE.

3

2

1

2

3M100A

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COMPRESSURE FAILURE

Y1

RC

1M5106A

THERMOSTAT SUBBASE SYSTEM COMPONENTS

B

Y2

W2

RH

H1 ANTICIPATOR

H2 ANTICIPATOR

C1

RISE

H1 FALL

FALL

H2

C2

RISE

C2 ANTICIPATOR

C1 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

T874A IS SINGLE-STAGE (NO W2 OR Y2).

O

A

AUTO

ON

FAN

SWITCH

SYSTEM

SWITCH

OFF

CHANGEOVER

RELAY

HEAT RELAY 1

COMPRESSOR

CONTACTOR 1

HEAT RELAY 2

L1

(HOT)

L2 1

COMPRESSOR

CONTACTOR 2

AUTO

HEAT

SERVICE

LED (RED)

W1

G

L1

(HOT

)

1

L2

CHANGEOVER

RELAY

FAN RELAY

2

SYSTEM MONITOR

COOL

1

6

9

10

11

4

8

2

Contents

Main PRODUCT DATA T874 Multistage Thermostats and Q674 Subbases APPLICATION FEATURES Contents ORDERING INFORMATION SPECIFICATIONS Super Tradeline/Tradeline Models Super Tradeline Models Tradeline Models Standard Models Page Page Page MERCURY NOTICE INSTALLATION When Installing this Product Location Mount Subbase Wire Subbase Page Outdoor Disconnect Install and Adjust Stop Brackets Mount Thermostat SETTINGS Set the Heat Anticipator Temperature Setting Subbase Setting Setting the Adjustable Differential Verify the Adjustment Heating CHECKOUT Heating Cooling Fan Outdoor Reset Thermistor (Where Applicable) CALIBRATION Thermostat Thermometer UNDERSTANDING CIRCUITS Tracing Method: Page Fig. 18. Tracing the changeover relay circuit. Fig. 19. Tracing the heat 1 and anticipation circuit. Fig. 20. Tracing the heat 1 anticipation circuit. Fig. 21. Tracing the heat 2, anticipation and AUX. HT. LED circuit. Fig. 22. Tracing the emergency heat and EM. HT. LED circuit. Fig. 23. Tracing the cooling circuit. Fig. 24. Tracing the auto fan circuit. Fig. 25. Tracing the fan on circuit. OPERATION Heat Anticipation/Cool Anticipation Interstage Differential Droop Outdoor Reset Service and Replacement of C815A Outdoor Thermistor 80 50 60 70 80 Features LED Indicators Restricted Setpoint (DoD) Commercial Rooftop Application Heat Pump Application Space Temperature Sensing Low Voltage Controls Two-Stage Thermostat Cycling Rate Voltage Anticipation Outdoor Reset Outdoor ResetHow it Works Changeover Low Temperature Lockouts COP = Heat Pumps with Dual Compressors Two speed Heat Pump Defrost Control Defrosting Defrost Control Functions Auxiliary Heat Two-Stage Thermostat Stage or Time Modulated Control Three-Stage Thermostat Emergency Heat Switching to Emergency Heat Crankcase Heat Compressor Fault Relay CROSS REFERENCE Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page Page WIRING DIAGRAMS Fig. 44. Schematic and hookup of T874A,B,C,D,E,F with Q674B. Used in standard applications. Fig. 45. Schematic and hookup of T874C,D with Q674B. Used in standard applications. Fig. 46. Schematic and hookup of T874A,B,D with Q674B. Used in standard applications. . Fig. 47. Schematic and hookup of T874R with Q674B. Used in heat pump applications. Fig. 48. Schematic and hookup of T874D with Q674B. Used in standard applications. Fig. 49. Schematic and hookup of T874C with Q674B. Used in standard applications. Fig. 50. Schematic and hookup of T874G with Q674B. Used in heat pump applications. Fig. 51. Schematic and hookup of T874D with Q674B. Used in standard applications. Fig. 52. Schematic and hookup of T874C with Q674B. Used in standard applications. Fig. 53. Schematic and hookup of T874D with Q674B. Used in standard applications. Fig. 54. Schematic and hookup of T874W with Q674B. Used in standard applications. Fig. 55. Schematic and hookup of T874A,D,F with Q674D. Used in standard applications. Fig. 56. Schematic and hookup of T874C with Q674B. Used in standard applications. Fig. 57. Schematic and hookup of T874P with Q674B. Used in heat pump applications. Fig. 58. Schematic and hookup of T874G with Q674D. Used in standard applications. Fig. 59. Schematic and hookup of T874A with Q674Q. Used in fan coil applications. Fig. 60. Schematic and hookup of T874C with Q674N. Used in evaporative cooler applications. Fig. 61. Schematic and hookup of T874C with Q674N. Used in evaporative cooler applications. Fig. 62. Schematic and hookup of T874F with Q674B. Used in wood/coal applications. Fig. 63. Schematic and hookup of T874F with Q674D. Used in wood/coal applications. Fig. 64. Schematic and hookup of T874A with Q674Q. Used in fan coil applications. Fig. 65. Schematic and hookup of T874A with Q674B. Used in standard applications. Fig. 66. Schematic and hookup of T874A,D,F with Q674D. Used in standard applications. Fig. 67. Schematic and hookup of T874R with Q674B. Used in heat pump applications. Fig. 68. Schematic and hookup of T874P with Q674B. Used in heat pump applications. Fig. 69. Schematic and hookup of T874V with Q674R. Used in fan coil applications. Fig. 70. Schematic and hookup of T874C with Q674S. Used in heat pump applications. Fig. 71. Schematic and hookup of T874A-D with Q674A. Used in standard applications. Fig. 72. Schematic and hookup of T874D,E,F with Q674C. Used in standard applications. Fig. 73. Schematic and hookup of T874G with Q674C. Used in heat pump applications. Fig. 74. Schematic and hookup of T874H with Q674C. Used in heat pump applications. Fig. 75. Schematic and hookup of T874A with Q674C. Used in standard applications. Fig. 76. Schematic and hookup of T874A-D with Q674C. Used in standard applications. Fig. 77. Schematic and hookup of T874K with Q674C. Used in heat pump applications. Fig. 78. Schematic and hookup of T874P with Q674C. Used in heat pump applications. Fig. 79. Schematic and hookup of T874G,H with Q674C. Used in standard applications. Fig. 80. Schematic and hookup of T874D with Q674E. Used in standard applications. Fig. 81. Schematic and hookup of T874C with Q674C. Used in heat pump applications. Fig. 82. Schematic and hookup of T874A,C,D with Q674E. Used in standard applications. Fig. 83. Schematic and hookup of T874G with Q674C. Used in standard applications. Fig. 84. Schematic and hookup of T874G with Q674E. Used in heat pump applications. Fig. 85. Schematic and hookup of T874A-D with Q674E. Used in standard applications. Fig. 86. Schematic and hookup of T874G with Q674E. Used in heat pump applications. Fig. 87. Schematic and hookup of T874D with Q674E. Used in standard applications. Fig. 88. Schematic and hookup of T874B,D with Q674E. Used in standard applications. Fig. 89. Schematic and hookup of T874D with Q674E. Used in standard applications. Fig. 90. Schematic and hookup of T874D with Q674G. Used in standard applications. Fig. 91. Schematic and hookup of T874A-F,Q with Q674G. Used in standard applications. Fig. 92. Schematic and hookup of T874C with Q674G. Used in heat pump applications. Fig. 93. Schematic and hookup of T874D with Q674K. Used in standard applications. Fig. 94. Schematic and hookup of T874D with Q674G. Used in standard applications. Fig. 95. Schematic and hookup of T874F with Q674K. Used in wood/oil applications. Fig. 96. Schematic and hookup of T874C with Q674C. Used in standard applications. Fig. 97. Schematic and hookup of T874P with Q674C. Used in heat pump applications. Fig. 98. Schematic and hookup of T874D with Q674E. Used in standard applications. Fig. 99. Schematic and hookup of T874C with Q674C. Used in standard applications. Fig. 100. Schematic and hookup of T874W with Q674C. Used in standard applications. Fig. 101. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 102. Schematic and hookup of T874J,R with Q674L. Used in heat pump applications. Fig. 103. Schematic and hookup of T874G with Q674L. Used in heat pump applications. Fig. 104. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 105. Schematic and hookup of T874C with Q674L. Used in heat pump applications. Fig. 106. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 107. Schematic and hookup of T874D with Q674L. Used in heat pump applications. Fig. 108. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 109. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 110. Schematic and hookup of T87C,R with Q674L. Used in heat pump applications. Fig. 111. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 112. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 113. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 114. Schematic and hookup of T874D with Q674L. Used in heat pump applications. Fig. 115. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 116. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 117. Schematic and hookup of T874D with Q674L. Used in heat pump applications. Fig. 118. Schematic and hookup of T874W with Q674L. Used in heat pump applications. Fig. 119. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 120. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 121. Schematic and hookup of T874C with Q674L. Used in heat pump applications. Fig. 122. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 123. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 124. Schematic and hookup of T874J with Q674L. Used in heat pump applications. Fig. 125. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 126. Schematic and hookup of T874G with Q674P. Used in heat pump applications. Fig. 127. Schematic and hookup of T874C with Q674L. Used in heat pump applications. Fig. 128. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 129. Schematic and hookup of T874G with Q674L. Used in heat pump applications. Fig. 130. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 131. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 132. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 133. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 134. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 135. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 136. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 137. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 138. Schematic and hookup of T874L with Q674B. Used in heat pump applications. Fig. 139. Schematic and hookup of T874D with Q674F. Used in heat pump applications. Fig. 140. Schematic and hookup of T874W with Q674L. Used in heat pump applications. Fig. 141. Schematic and hookup of T874C with Q674F. Used in standard applications. Fig. 142. Schematic and hookup of T874C,D with Q674F. Used in standard applications. Fig. 143. Schematic and hookup of T874G with Q674B. Used in heat pump applications. Fig. 144. Schematic and hookup of T874J with Q674J. Used in heat pump applications. Fig. 145. Schematic and hookup of T874G with Q674F. Used in heat pump applications. Fig. 146. Schematic and hookup of T874D with Q674F. Used in heat pump applications. Fig. 147. Schematic and hookup of T874G with Q674F. Used in heat pump applications. Fig. 148. Schematic and hookup of T874G with Q674F. Used in heat pump applications. Fig. 149. Schematic and hookup of T874C with Q674F. Used in heat pump applications. Fig. 150. Schematic and hookup of T874G with Q674F. Used in heat pump applications. Fig. 151. Schematic and hookup of T874G with Q674F. Used in heat pump applications. Fig. 152. Schematic and hookup of T874D with Q674F. Used in standard applications. Fig. 153. Schematic and hookup of T874G with Q674F. Used in heat pump applications. Fig. 154. Schematic and hookup of T874G with Q674F. Used in heat pump applications. Fig. 155. Schematic and hookup of T874G with Q674F. Used in heat pump applications. Fig. 156. Schematic and hookup of T874G with Q674F. Used in heat pump applications. Fig. 157. Schematic and hookup of T874G with Q674F. Used in heat pump applications. Fig. 158. Schematic and hookup of T874G with Q674F. Used in heat pump applications. Fig. 159. Schematic and hookup of T874G with Q674J. Used in heat pump applications. Fig. 160. Schematic and hookup of T874G with Q674J. Used in heat pump applications. Fig. 161. Schematic and hookup of T874G with Q674J. Used in heat pump applications. Fig. 162. Schematic and hookup of T874G with Q674J. Used in heat pump applications. Fig. 163. Schematic and hookup of T874G with Q674C. Used in standard applications. Fig. 164. Schematic and hookup of T874H with Q674C. Used in standard applications. Fig. 165. Schematic and hookup of T874L with Q674C. Used in heat pump applications. Fig. 166. Schematic and hookup of T874D with Q674F. Used in standard applications. Fig. 167. Schematic and hookup of T874G with Q674F. Used in heat pump applications. Fig. 168. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 169. Schematic and hookup of T874G with Q674F. Used in heat pump applications. Fig. 170. Schematic and hookup of T874G with Q674F. Used in heat pump applications. Fig. 171. Schematic and hookup of T874J with Q674J. Used in heat pump applications. Fig. 172. Schematic and hookup of T874H with Q674B. Used in heat pump applications. Fig. 173. Schematic and hookup of T874H with Q674C. Used in heat pump applications. Fig. 174. Schematic and hookup of T874G with Q674J. Used in heat pump applications. Fig. 175. Schematic and hookup of T874G with Q674J. Used in heat pump applications. Fig. 176. Schematic and hookup of T874G with Q674C. Used in standard applications. Fig. 177. Schematic and hookup of T874G,H with Q674C. Used in standard applications. Fig. 178. Schematic and hookup of T874N with Q674F. Used in heat pump applications. Fig. 179. Schematic and hookup of T874N with Q674F. Used in heat pump applications. Fig. 180. Schematic and hookup of T874A,D with Q674J. Used in heat pump applications. Fig. 181. Schematic and hookup of T874K with Q674C. Used in heat pump applications. Fig. 182. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 183. Schematic and hookup of T874G with Q674J. Used in heat pump applications. Fig. 184. Schematic and hookup of T874A,F with Q674G. Used in standard applications. Fig. 185. Schematic and hookup of T874D with Q674E. Used in standard applications. Fig. 186. Schematic and hookup of T874D with Q674G. Used in standard applications. Fig. 187. Schematic and hookup of T874C with Q674B. Used in standard applications. Fig. 188. Schematic and hookup of T874D with Q674G. Used in standard applications. Fig. 189. Schematic and hookup of T874F with Q674D. Used in standard applications. Fig. 190. Schematic and hookup of T874C with Q674L. Used in heat pump applications. Fig. 191. Schematic and hookup of T874R with Q674B. Used in heat pump applications. Fig. 192. Schematic and hookup of T874D with Q674C. Used in standard applications. Fig. 193. Schematic and hookup of T874D with Q674E. Used in standard applications. Fig. 194. Schematic and hookup of T874G with Q674F. Used in heat pump applications. Fig. 195. Schematic and hookup of T874G with Q674F. Used in heat pump applications. Fig. 196. Schematic and hookup of T874G with Q674J. Used in heat pump applications. Fig. 197. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 198. Schematic and hookup of T874L with Q674E. Used in standard applications. Fig. 199. Schematic and hookup of T874G with Q674F. Used in heat pump applications. Fig. 200. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 201. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 202. Schematic and hookup of T874D with Q674G. Used in standard applications. Fig. 203. Schematic and hookup of T874L with Q674C. Used in heat pump applications. Fig. 204. Schematic and hookup of T874D with Q674F. Used in standard applications. Fig. 205. Schematic and hookup of T874H with Q674C. Used in heat pump applications. Fig. 206. Schematic and hookup of T874J with Q674J. Used in heat pump applications. Fig. 207. Schematic and hookup of T874J with Q674L. Used in heat pump applications. Fig. 208. Schematic and hookup of T874D with Q674D. Used in standard applications. Fig. 209. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 210. Schematic and hookup of T874Y with Q674E. Used in heat pump applications. Fig. 211. Schematic and hookup of T874G with Q674F. Used in standard applications. Fig. 212. Schematic and hookup of T874A with Q674E. Used in standard applications. Fig. 213. Schematic and hookup of T874L with Q674C. Used in heat pump applications. Fig. 214. Schematic and hookup of T874A with Q674B. Used in standard applications. Fig. 215. Schematic and hookup of T874L with Q674B. Used in heat pump applications. Fig. 216. Schematic and hookup of T874G with Q674J. Used in heat pump applications. Fig. 217. Schematic and hookup of T874N with Q674C. Used in heat pump applications. Fig. 218. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 219. Schematic and hookup of T874C with Q674C. Used in standard applications. Fig. 220. Schematic and hookup of T874W with Q674C. Used in standard applications. Fig. 221. Schematic and hookup of T874H with Q674C. Used in heat pump applications. Fig. 222. Schematic and hookup of T874B with Q674E. Used in standard applications. Fig. 223. Schematic and hookup of T874S with Q674F. Used in heat pump applications. Fig. 224. Schematic and hookup of T874A,D with Q674E. Used in standard applications. Fig. 225. Schematic and hookup of T874D with Q674C. Used in standard applications. Fig. 226. Schematic and hookup of T874G with Q674G. Used in standard applications. Fig. 227. Schematic and hookup of T874G with Q674F. Used in heat pump applications. Fig. 228. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 229. Schematic and hookup of T874G with Q674F. Used in heat pump applications. Fig. 230. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 231. Schematic and hookup of T874G with Q674F. Used in heat pump applications. Fig. 232. Schematic and hookup of T874D with Q674G. Used in standard applications. Fig. 233. Schematic and hookup of T874W with Q674L. Used in heat pump applications. Fig. 234. Schematic and hookup of T874G with Q674B. Used in heat pump applications. Fig. 235. Schematic and hookup of T874G and Q674F. Used in heat pump applications. Fig. 236. Schematic and hookup of T874A-D with Q674C. Used in standard applications. Fig. 237. Schematic and hookup of T874C with Q674B. Used in standard applications. Fig. 238. Schematic and hookup of T874C with Q674F. Used in heat pump applications. Fig. 239. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 240. Schematic and hookup of T874A with Q674W. Used in standard applications. Fig. 241. Schematic and hookup of T874J with Q674L. Used in heat pump applications. Fig. 242. Schematic and hookup of T874G with Q674C. Used in standard applications. Fig. 243. Schematic and hookup of T874G with Q674F. Used in heat pump applications. Fig. 244. Schematic and hookup of T874J with Q674J. Used in heat pump applications. Fig. 245. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 246. Schematic and hookup of T874C with Q674G. Used in standard applications. Fig. 247. Schematic and hookup of T874W with Q674L. Used in heat pump applications. Fig. 248. Schematic and hookup of T874Y with Q674F. Used in heat pump applications. 60-24858 J.H. Rev. 3-01 www.honeywell.com Home and Building Control Home and Building Control Fig. 249. Schematic and hookup of T874C with Q674B. Used in heat pump applications.