Help with wiring from Honeywell T874C to RTH7500
#1
10-03-10, 05:19 PM
Join Date: Oct 2010
Location: United States
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Help with wiring from Honeywell T874C to RTH7500
I am new in this forum and just purchased a Honeywell RTH7500 programmable thermostat to upgrade my current Honeywell T874C with Q674F base. Currently my wiring coming into the base is as follows
W1---Blue
W2---White
G-----Green
R-----Red
O-----Orange
Y1----Yellow
E-----Brown
X1----Black
X2 and E jumpered
How should they be wired in the 7500?
My unit is a two stage heating, single stage cooling heat pump with E-heat.
Any help will be most appreciated.
Robin
W1---Blue
W2---White
G-----Green
R-----Red
O-----Orange
Y1----Yellow
E-----Brown
X1----Black
X2 and E jumpered
How should they be wired in the 7500?
My unit is a two stage heating, single stage cooling heat pump with E-heat.
Any help will be most appreciated.
Robin
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#2
10-03-10, 06:01 PM
Forum Topic Moderator
Post the control wiring connections at the air handler.
Seems like the old stat should have been wired differently to me.
I see that you have a different color code then this example, but the blue wire on W1 should be checked.
Seems like the old stat should have been wired differently to me.
I see that you have a different color code then this example, but the blue wire on W1 should be checked.
#3
10-03-10, 07:11 PM
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Will be tomorrow afternoon before I can get the control wiring. I did notice that the pdf you showed is for a T874D instead of a T874C. Does it make any difference?
Thanks,
Robin
Thanks,
Robin
#4
10-03-10, 08:59 PM
Forum Topic Moderator
The Q674F is the subbase and has the terminals on it.
The T874C would have two stage heat and one stage cooling. The T874D has 2 stage heat and 2 stage cooling.
The T874C would have two stage heat and one stage cooling. The T874D has 2 stage heat and 2 stage cooling.
#6
10-04-10, 05:22 PM
Forum Topic Moderator
The Y2 terminal will not function when using a T874C.
The blue wire on your W1 terminal should have only been a jumper to Y1.
If it connects to anything else, this should be checked at the air handler.
otherwise...
Aux = white
G = green
Rc & R = red
O/B = orange
Y = yellow
E = brown
C = black
tape off blue
option 170 = 7
option 190 = 0
Remove power to the air handler before replacing the stat.
The blue wire on your W1 terminal should have only been a jumper to Y1.
If it connects to anything else, this should be checked at the air handler.
otherwise...
Aux = white
G = green
Rc & R = red
O/B = orange
Y = yellow
E = brown
C = black
tape off blue
option 170 = 7
option 190 = 0
Remove power to the air handler before replacing the stat.
#7
10-13-10, 01:46 PM
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Help with wiring from Honeywell T874C to RTH7500
The blue wire from W1 goes to the air handler and connects with another blue wire and two white wires (W2) and connects to a violet wire. This violet wire connects to another larger gauge blue wire and connects to pin 7 of R1. Does this help clarify matters? Sorry for my delay, been dealing with a family death.
Robin
Robin
#8
10-13-10, 06:57 PM
Forum Topic Moderator
What is the make and model number of your air handler and outdoor unit?
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