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Old 08-07-2013, 07:21 PM   #1
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Changing from an old to new thermostat


I have a Trane XE 1200 and I'm trying to replace an old thermostat with a new Honeywell RTH6350D. I thought that I could just use the old wiring color code from the exhisting but they do not match with the new Honeywell.
Here is how the old one looked;
HVAC wiring - W Y G R
Theremostat - O B Y W G RH RC (7 terminals)
So in case the letters do not match up to one above the other, white wire to O, Yellow to Y and Y and W had a jumper and RH and RC also have a jumper, green wire to G, and red wire to the RC terminal.
The new Honeywell has a connection like this; Y2 W2 G W - Y R RC (8 terminals and the "-" terminal says "not used"
Could someone help me out on this please?

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Old 08-07-2013, 07:37 PM   #2
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Changing from an old to new thermostat


Lets start from the beginning. How many wires are there connected to the old thermostat (Pictures work really good in these situations), where are the wires connected to what terminals, regardless what color they are (this is the reason that white masking tape & ink pens were invented, same goes for the little labels that come with new thermostats).

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Old 08-07-2013, 07:42 PM   #3
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Changing from an old to new thermostat


Turn off power to ac/heating first before doing anything. Make sure you mark wires properly before you remove them. This video maybe helpful, if not post some pics for the pro's to see. Thanks.

replacing old theromostat with new one
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Old 08-08-2013, 09:23 AM   #4
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Changing from an old to new thermostat


Quote:
Originally Posted by gregzoll View Post
Lets start from the beginning. How many wires are there connected to the old thermostat (Pictures work really good in these situations), where are the wires connected to what terminals, regardless what color they are (this is the reason that white masking tape & ink pens were invented, same goes for the little labels that come with new thermostats).
Is this a heat pump?

From the OP, he's got
white = O terminal
unused = B terminal
yellow = W+Y terminals
red = RC+RH terminals
green = G terminal


If the system is working properly, does he need to track down those four wires in the air handler, or should we already know where those wires end up? (I think white goes to the OD unit's reversing valve signal, yellow to the heat and cool terminals in the AH and the contactor signal in the OD, green to fan in the AH, and red to the 24v power source in the AH, but I'm confused as to how the blue/common wire is handled, unless it runs to the outdoor unit but not the t-stat)

It sounds like he has a single stage system and a multistage replacement t-stat and the 2nd stage terminals are confusing him.

Last edited by taxmantoo; 08-08-2013 at 05:06 PM.
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Old 08-16-2013, 12:31 AM   #5
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Changing from an old to new thermostat


Thanks guys! After all of that we had already had an hvac guy coming the next day but I was trying to head him off at the pass and get it done without having to spend the cash. Good thing is that I now know how to do it!
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