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
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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
MERCURY NOTICE
INSTALLATION
When Installing this Product
Location
Mount Subbase
Wire Subbase
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Outdoor Disconnect
ithin
remains
Install and Adjust Stop Brackets
not
SETTINGS
Set the Heat Anticipator
Temperature Setting
Subbase Setting
Setting the Adjustable Differential
wider
larger
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
anticipates
current anticipation
voltage anticipation
Service and Replacement of C815A Outdoor Thermistor
80 50 60 70 80
Features
LED Indicators
This must be done during installation.
Commercial Rooftop Application
Enthalpy
Heat Pump Application
Space Temperature Sensing Low Voltage Controls
Two-Stage Thermostat
Cycling Rate
Voltage Anticipation
designed into
Outdoor Reset
Outdoor ResetHow it Works
Low Temperature Lockouts
COP =
Heat Pumps with Dual Compressors
Two speed Heat Pump
Defrost Control
Defrosting
Defrost Control Functions
quipment safety
economy of operation
Stage or Time Modulated Control
Outdoor thermostats
time modulated
thermostat jiggler
Three-Stage Thermostat
Crankcase Heat
Compressor Fault Relay
CROSS REFERENCE
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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
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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.
W1 G RC W3 W2 F RH B O Y1
COMPRESSOR CONTACTOR
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.
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R
B
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.hone y
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Fig. 249. Schematic and hookup of T874C with Q674B. Used in heat pump applications.
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES