I am trying to replace my thermostat and need help.

my old thermostat is a T874R with Q674L sub. The wiring diagram can be seen here.

http://customer.honeywell.com/techli...0s/60-1152.pdf

Page 9, Fig. 14.

T is not used.

All other wires are present (W2, G, R, X, Z, K, Y, W1)

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My new thermostat is RTH7600D. The installation instructions are here.

http://customer.honeywell.com/techli.../69-2206ES.pdf

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I can not figure out the configuation that I need. Any help would be appreciated.

-Greg

Are you having trouble wiring it or configuring the new tstat? Please describe your system (HP, furnace, air handler, etc.)? Manufacturers and models would be helpful.

Without knowing what you have its hard to tell you how to configure your tstat.

Here are the directions for your old subbase/thermostat. Just transpose the wiring from the old as posted to the new unit.


http://customer.honeywell.com/techli...0s/69-0272.pdf

It is a heat pump made by intertherm. I cannot access the model number right now. I might be able to get it when I get home.

I am not sure about the wiring, My thoughts are

old=new
R=R
Y=Y
G=G
X=C?
Z=L?
W1=B?
K=E?
W2=Aux?

Am I close?

update:

This is a revised list after a little more insight...

old=new
R=R
Y=Y
G=G
X=C (common)
Z=unused (LED for Service)
W1=O
K=unused (LED for Em. Heat)
W2=Aux

Jump E and Aux together.

Is this correct?

Almost... W1-O? A heat pump will require either B or O for the reversing circuit (usually O). Connecting W1 to O will activate auxiliary heat when thermostat is set to cool. Post wire colors that correspond to old.

So, W1 should be B?

W1 should not be either O or B. Post wire colors that correspond to old.

R=Red
Y=Yellow
G=Green
X=Black
Z=Tan/Brown
W1=White
K=Orange
W2=Blue

The reason I say that the W1 is B is because on the diagram it shows it between the Heat Changeover Valve and the rise/fall switches

While variations are possible, the orange wire is most commonly used for the reversing circuit (hence the "O" terminal designation). Does your new t-stat have an "O" terminal? It may be combined with "B", look closely...

It has an "O/B" designation.

Quote:

---

Originally Posted by greoryg

update:

This is a revised list after a little more insight...

old=new
R=R
Y=Y
G=G
X=C (common)
Z=unused (LED for Service)
W1=O
K=unused (LED for Em. Heat)
W2=Aux

Jump E and Aux together.

Is this correct?

---

After looking carefully at both manuals, this is the mapping I'd guess at. To be sure you can wire it up in stages: first just power, then add the fan, then your aux heat only, then your HP. If you can't figure the Hp immediately you'll have aux heat.

I would suggest you re-consult with hvac1000 as he has unlimited access to technical references that might reveal something unconventional about your arrangement.

These are pictures of the front panel in my unit.

http://www.flickr.com/photos/33738050@N08/3133614703/
http://www.flickr.com/photos/33738050@N08/3133618359/
http://www.flickr.com/photos/33738050@N08/3134440320/
http://www.flickr.com/photos/33738050@N08/3134441810/

Quote:

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Originally Posted by greoryg

These are pictures of the front panel in my unit.

http://www.flickr.com/photos/33738050@N08/3133614703/
http://www.flickr.com/photos/33738050@N08/3133618359/
http://www.flickr.com/photos/33738050@N08/3134440320/
http://www.flickr.com/photos/33738050@N08/3134441810/

---

Attachments won't open.

Trying again...

P1000438 on Flickr - Photo Sharing!
P1000441 on Flickr - Photo Sharing!
P1000443 on Flickr - Photo Sharing!
P1000442 on Flickr - Photo Sharing!

Merry Christmas to you and yours.

-Greg

Are the photos any help in solving the case?

Actually I do not see a case to solve. Tape off K and Z and then wire it according to the instructions in the new stat. Then make selections settings for your unit as in O or B? etc. The old subbase drawing shows what the old terminals were used for so just transpose them to the new thermostat.