Honeywell T874G to Honeywell T8611G - http://www.hvacmechanic.com/ Forums
Original message
| someara
 |  "Honeywell T874G to Honeywell T8611G"
, posted Mon 3 Nov 23:48  
Please help! We are replacing our old heat pump thermostat which was a Honeywell T874G (It has "York" on it, but it looks exactly like the Honeywell and the number inside says T874G). We want to replace it with a programmable heat pump thermostat. So, the Honeywell Chronotherm IV T8611G was recommended. We are not sure exactly how to hook up the wires. When we open our OLD thermostat we have the following colored wires: yellow, green, orange, blue, white, red and pink. So, we know where some of the wires go, but not sure about others. My husband is an electrical engineer so he knows HOW to hook them up but doesn't know WHERE to hook them up! :)
What we have figured out so far is:
yellow --> compressor contactor
green --> fan relay
orange --> cooling or heating changover valve (???)
white --> heat relay 1
red --> L1 (hot!)
pink --> ?
blue --> ?
Any advice about how to hook this up would be great. Technical info on our new (and old) thermostat can be located on Honeywell's website.
http://hbctechlit.honeywell.com/Search_Results.cfm
Thanks!
Dave and Shannon
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Replies:
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| someara
| "Re(1):Honeywell T874G to Honeywell T8611G" , posted Wed 5 Nov 21:09
Our new thermostat has C, Y1, G, O/B, E, W2, W1, R, X1, X2, L
Our old one has: O, G, R, W, X, B, Y
Our old thermostat had an O and a B so we are confused about this O/B on the new T8611.
Thanks! We are getting there. :)
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| someara
| "Re(1):Honeywell T874G to Honeywell T8611G" , posted Wed 5 Nov 12:32
Ok, I found out some more info. We have a T874G thermostat with a Q674J subase. The wiring diagram of what we currently have installed is at the following link (see fig 160 on page 168)
http://hbctechlit.honeywell.com/techlit/PDF/60-0000s/60-2485.pdf
But you probably already know all of this!! :)
Just to doublecheck, the chronotherm iv T8611G IS an appropriate replacement for this thermostat and subase, right?
Also, any more advice on the hookup would be appreciated now that I gave you more pertinent info (the subase). We have a call into a local tech center as well, but haven't heard back yet. Thanks so much for your time and expertise! Let me know if I have left anything important out.
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| | Xenos
Webmaster 
| "Re(2):Honeywell T874G to Honeywell T8611G" , posted Wed 5 Nov 20:00
These 2 thermostats are virtually identical. The only differences will be W1 on the original thermostat is now labeled W2 and the original C is now labeled C/X. For some reason I think there may be 2 versions of the T8611G one with W1 one without. This information is for the one that does not have a W1 if a W1 is present it must be jumped to Y.
Xenos.
The best way to escape a problem is to solve it.
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| Xenos
Webmaster
| "Re(1):Honeywell T874G to Honeywell T8611G" , posted Tue 4 Nov 18:50
It really depends on the old sub base the number will be Q674X. The colors don’t mean any thing it’s where they’re connected. On the older Q674X sub bases Y powered the compressor in both heating and cooling. With you new thermostat you will need to jump out Y1 and W1 to accomplish this as well on the older systems W1 was the heating change over valve this is now B. As well the option for staging electric heat relays are not available on the T8611G therefore W3 will no longer exist and all Aux heating wires will have to connect to W2.
Xenos.
The best way to escape a problem is to solve it.
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| | Xenos
Webmaster
| "Re(2):Honeywell T874G to Honeywell T8611G" , posted Wed 5 Nov 22:12
Ok I’m upset and confused with Honeywell. I have just found 4 different wiring diagrams for the T8611G.
Ok Lets see if this makes sense
Old thermostat / New thermostat.
X= C
R=R
W=? read below
O or B= B/O
Y=Y
G=G
Ok lets start with this W1, On the diagram I have with the B/O being the same terminal it appears as though they have went back to using Y for the compressor in both heating and cooling. Therefore W1 is now the same as the original W and they added W2 as a third stage.
The B/O is selectable in the programming menu, since O ( cooling changeover) was your original changeover Option 29 is defaulted to O and can be changed to B( heating changeover) by selection 1 instead of 0.
Xenos.
The best way to escape a problem is to solve it.
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| | someara
| "Re(3):Honeywell T874G to Honeywell T8611G" , posted Wed 5 Nov 23:47
this is all starting to come together. But what should we do with the B wire? Since we have 7 existing wires in our old unit. So what we have so far is.... old/new
X = C
R = R
W = W1
O = B/O
Y = Y
G = G
B = ?
Thanks
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| | tss103
| "Re(4):Honeywell T874G to Honeywell T8611G" , posted Thu 6 Nov 19:36
Hi, I am replacing a T874R/Q674L with a T8611G.
I have been told by Honeywell to match like this:
R TO R
Y TO Y, leave jumper from Y to W1
W TO W2
G TO G
O TO O/B
B TO C
X TO E
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| | Xenos
Webmaster
| "Re(5):Honeywell T874G to Honeywell T8611G" , posted Fri 7 Nov 16:51
Something doesn’t seam to jive with that B to C and X to E. What sub base is the old one.. Q674X ?
Xenos.
The best way to escape a problem is to solve it.
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| | tss103
| "Re(6):Honeywell T874G to Honeywell T8611G" , posted Fri 7 Nov 20:52
The sub base on my existing thermostat is Q674L 1272
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| | Xenos
Webmaster
| "Re(7):Honeywell T874G to Honeywell T8611G" , posted Sat 8 Nov 07:52
I have just reviewed all the diagrams, X = C on 3 out of 4 of their sub bases on the other, X is a service light. As it’s defiantly not B.
Now B may be E since B is for heating change over and E is emergency heat. If your heat pump uses an emergency heat relay then this should be correct. Using X to E doesn’t make sense with any of the diagrams I have just looked at since E is power out.
Xenos.
The best way to escape a problem is to solve it.
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| | Xenos
Webmaster
| "Re(8):Honeywell T874G to Honeywell T8611G" , posted Sat 8 Nov 12:30
Just found out York and Luxair use B as C on their furnaces. I would say your origional post is correct. Honeywell must have made that subbase for them and they don't support it in their wiring documents online.
Xenos.
The best way to escape a problem is to solve it.
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| | someara
| "Re(9):Honeywell T874G to Honeywell T8611G" , posted Sat 8 Nov 21:24
I hooked up our thermostat as tss103 first suggested a couple of days ago. The system test all worked fine: the different parts came on as they should
It has been operating great (as far as we can tell) ever since. Thanks to both of you for all of your advice!
Shannon
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| | Xenos
Webmaster
| "Re(10):Honeywell T874G to Honeywell T8611G" , posted Sat 8 Nov 21:36
Yes I owe TSS an apology on that one he was righ on the money and I learned something from it.
Xenos.
The best way to escape a problem is to solve it.
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| | someara
| "Re(2):Re(10):Honeywell T874G to Honeywell T86" , posted Sat 8 Nov 22:30
Well it sure seems as though Honeywell didn't make it very easy on any of us! I did a ton of research through their tech manuals and the more I learned, the more confused I became. All's well that ends well. :)
Shannon
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| | tss103
| "Re(3):Re(10):Honeywell T874G to Honeywell T86" , posted Sun 9 Nov 18:55
Thanks, forums like this are an enormous help and I'm glad this resource is available.
I just got my stats hooked up and everything seems to work ok. The installer tests worked fine except the emergency heat test is not producing heat. Shouldn't it? The fan comes on and just puts out ambient temp. air.
When I set the system setting to emergency heat, it certainly puts out a lot of heat.
Any thoughts?
Tom
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| | Xenos
Webmaster
| "Re(4):Re(10):Honeywell T874G to Honeywell T86" , posted Sun 9 Nov 20:27
If it all works except during the test mode. Ie switch the stat to emg heat and run it. I wouldn’t worry about it since the heat pump may have an emergency heat relay in it and it may not be activated during the test mode.
Xenos.
The best way to escape a problem is to solve it.
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