Thermostat-Honeywell RTH7000 Series wiring problems


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Old 04-14-08, 08:50 AM
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Thermostat-Honeywell RTH7000 Series wiring problems

This is my first attempt to seek advice from this forum, but since Ive gotten a lot of useful tips from reading it in recent times, I thought that maybe I could find the answer to a problem were having. In short, my son decided to replace his existing thermostat with a programmable Honeywell TRH7000 Series unit. Unfortunately, it appears that the wiring for the old thermostat was somewhat different than the new unit. Moreover, inasmuch as he lives in a different area from me, Im unable to physically help him. As a result weve been communicating via telephone and the internet but have not been successful. Ive made a few suggestions, but they apparently didnt work. Anyhow, heres the situation.

The old thermostat included the following 7 terminals connected to the color-coded wires as indicated:
B-blue
G-green
Y-yellow
U-orange
R-red
E-black
Y2-white (he says its beige, but Im presuming its a dirty white)
Nevertheless, before he disconnected anything, he marked all of the wiring so as to indicate from which terminal each wire was connected.

The Honeywell RTH 700 Series provides a PDF installation instructional manual online (http://customer.honeywell.com/techli.../69-2104ES.pdf) setting forth the following terminals:
R
RC
O/B
Y
G
C
L
E
AUX
The instructions indicate that R and RC include a jumper, and that the jumper is to remain in place. For the most part, these instructions are fairly clear and straightforward, but in some key areas the instructions fall short.

Specifically, the instructions make no mention of the possiblities of a terminal on the old thermostat named U. But since the new thermostat includes a terminal designated O/B, he connected the wire (orange) that was formerly connected to U, to O/B. Obviously, this was simply a guess, but it seemed to be the most reasinable chice given the options.

He connected the other wires to the terminals on the new thermostat as directed, namely:
B to C (per instructional manual)
G to G
Y to Y
R to R
E to E
Then, pursuant to the instructional manual, he connected a jumper between E and AUX.

The instructional manual provided no further directions that were helpful, but it was clear he had no where to attach the beige (or white) wire that had been connected to terminal Y2of the old thermostat. Needless to say, when he turned on the unit it didnt work.
He tried a second approach where he un-jumped E and AUX, and connected the beige (white) wire that was formerly connected to Y2, to AUX, but left E connected to E. That approach also failed.

Ive attempted to contact Honeywell and ask for some direction, but have not been successful. I have read on this forum where others have had problems wiring up an RTH 7000Series, but none of the other problems appear to be on point. I would appreciate any help from some of the more knowledgeable readers of this forum.

Thank you.
 
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Old 04-15-08, 03:21 AM
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Can you post the mfr & m/n of the old t-stat + subbase?

mfr & m/n for the indoor and outdoor units could be useful too, but at this time the info of the old t-stat first.
 
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Old 04-16-08, 02:11 PM
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Thank you for your interest. Unfortunately, my son says that although he does have the top section of the t/stat (housing the temperature sensing element and 4 mercury switches) he discarded the base plate because it was physically cracked and he unwisely believed he had replaced the new t/stat correctly. It seems, however, that he failed to test the a/c, and when weather warmed and he called for cold, it did not respond.
The part of the old t/stat (that he only kept because he wasn't certain how to safely dispose of the mercury switches) has neither a manufacturer's name nor obvious model number. It does contain a couple of unidentifiesd 6-digit numbers which he attempted to google in various ways but came up with nothing.
I was hoping that a more knowledgable person might know what the "U" terminal might have been, and possibly even have some suggestions as to what might terminal connections might work at this stage.
Tom
 
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Old 04-16-08, 05:50 PM
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Tom:
All bets are off when it comes to terminal designations for heat pumps. There's no standardization for them. Different manufacturers use different letters. The Honeywell RTH7000installation manual itself does not show any "U" terminals in the various wiring options presented. So if your son no longer has that subbase or cannot give you the M/N of the t-stat (which you say he's still keeping), and if you do not have handy the MFR & M/N of that heat pump's outdoor/indoor units, it will be real hard for anyone to help.
 
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Old 04-16-08, 08:54 PM
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Pflor-First, thank you for the advice thus far. It's greatly appreciated. And, importantly I hope, it looks like we might bwe making aa little progress.
It seems that my son didnt do that good of a job in his initial effort to identify the make/model of the old t/stat. It now appears that he has come up with some numbers and has correctly identified it as a Honeywell T 784 G with a Q 674subbase. Its not that he found the old subbase; that number was simply identified in the manual as the subbase that should be used with that t/stat. Ive sent a photo of the old t/stat to Yahoos Flickr and tagged it as old thermostat T874G and have set it up so that anyone can see that picture. Hopefully it will be available when you read this message. In any event, I will include a Honeywell hyperlink to a PDF of the t/stat and subbase manual for the identified t/stat and subbase at the bottom of this note.
I might add that I went through it but, for the life of me, I cant find any U terminal. Im wondering now if he mistook a V for a U. I'm sure that's possible.
Regardless, maybe the information in the manual will be more meaningful to you than it was to me, but quite candidly, I didnt find it that helpful.
I do appreciate the help so far, but if you have the opportunity to review this latest piece of information and could make some suggestions, wed greatly appreciate it.
Thank you,
Tom
http://www.iaqwholesale.com/manuals/...74/60-2485.pdf
 
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Old 04-17-08, 04:15 AM
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Pflor
As a follow-up to my earlier thoughts on that mysterious "U" terminal, I'm convincing myself that what he thought was a "U" was most likely an "O". I say this because it's reasonable to believe that the two letters could have easily been confused, but additionally, it was connected to an orange wire. I think I'd procedd along that line of thinking.
Tom
 
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Old 04-18-08, 03:53 AM
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There are no matches on the terminal designations you report for the wiring of the old subbase as per Honeywell.

If the orange wire is indeed an "O", then you should hook up either the "B" or the "O" but not both. The component they energize is the "reversing valve". Reversing valves come in either one of two presentations: "Reverse on Heat" or "Reverse on Cool" so only one of these two terminals is used.
 
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Old 04-18-08, 07:12 AM
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I can't believe what I've done.

Pflor
The next time I say to anyone, including my son, that I'll try to help them with something over the phone, I'm going to remind myself of this experience.
Anyhow, after reading your last response I spoke with my son about the designated wires that he had earlier advised me were advised me to certain terminals, and it seems that there was a miscommunication. The correct designation for the old terminals included a "C" not "B" I obviously misheard him.
Therefore, the seven terminals on the old t'stat would correctly be identified as follows: C G Y O R E Y2.

I'm embarrassed that I've gotten this so confused, but I guess we all make mistakes. Nevertheless, in light of this latest revelation, would this be consistent with Honeywell's designations, and if so, would there be enough information so as to possibly hook it up correctly?
I very much appreciate the time you've taken to help me with this.
Tom
 
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Old 04-18-08, 08:02 AM
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I believe we may be on the right track now.
I'm lecturing, but at some point later will look back at some pertinent info and will get back to you in the course of the day.
 
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Old 04-18-08, 08:18 AM
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Many thanks,
Tom
 
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Old 04-18-08, 12:37 PM
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After your clarification, all the terminals seem to have a nice n easy tit-for-tat connecting sequence, except for that Y2.

The question then is: Does this outdoor unit have 2-stages of cooling?...If its an older unit, I doubt it.
SoIs there a mistake here (I hope) and theres no Y2 terminal but it really has a different letter? (maybe a W)...if this is the case, it should be connected to the AUX terminal in the new thermostat.

Else, if the outdoor unit really has two stages of cooling, are we talking 2 compressors? or a single 2-speed compressor?
If there are 2 compressors, both, Y and Y2 should connect to the Y terminal on the new thermostat (you'll lose your staging, both compressors will be running). If it is a single 2-speed compressor, only one of the Y terminals should be connected there (Id go with the Y2 assuming that is for the higher speed)

Finally, nothing should be connected to that L terminal on the new thermostat.
 
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Old 04-18-08, 04:36 PM
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Going back to that Y and Y2 terminal issue, it could be quite helpful to know the MFR and full M/N of the outdoor unit. Hopefully the unit's manual is available online and I'd be able to check the type of compressor it really has. That in turn could help with the t'stat wiring of the Y terminals.
 
 

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