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Kcrand36
Kcrand36, HVAC Mechanic
Category: HVAC
Satisfied Customers: 77
Experience:  Owner at Advantage Repair
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Trying to install second RTH9580 tstat on 2 zone system, one

Customer Question

Trying to install second RTH9580 tstat on 2 zone system, one works other is just blinking Honeywell and shutting back off. Furnace makes buzzing sound with 2nd tstat on
Submitted: 9 months ago.
Category: HVAC
Expert:  Kcrand36 replied 9 months ago.
good Morning. I am Kevin, one of the tech's here on JA. What thermostats did you have before?
Customer: replied 9 months ago.
Honeywell Trolatemp Chromotherm 3
Customer: replied 9 months ago.
Just attached a photo of how the old was hooked up
Customer: replied 9 months ago.
Here is how the new one is connected, I've tried the white in both spots with same result
Expert:  Kcrand36 replied 9 months ago.
what type of heating system do you have? It looks like you have a heat pump....
Customer: replied 9 months ago.
It's a carrier, can't find a model number
Customer: replied 9 months ago.
Found it: CK5BXA048000AAAA
Expert:  Kcrand36 replied 9 months ago.
gas furnace?
Customer: replied 9 months ago.
Yes, gas
Expert:  Kcrand36 replied 9 months ago.
ok, you have a two zone system, so you must have a zone board as well? Usually located on the side or near the furnace.
Customer: replied 9 months ago.
What would that look like, this system has a humidifier and air cleaner and all kinds of stuff attached to it
Customer: replied 9 months ago.
Is this it?
Expert:  Kcrand36 replied 9 months ago.
yes, I believe so, can you take the cover off and take a picture of the wiring there as well.
Customer: replied 9 months ago.
Hopefully that helps, it's behind my softener and hard to get to
Expert:  Kcrand36 replied 9 months ago.
is there a model number on that trol a temp?
Customer: replied 9 months ago.
MM-2
Expert:  Kcrand36 replied 9 months ago.
ok, what I am seeing is that the thermostat that you showed in your first image is the "controlling thermostsat" or change over thermostat. I'm not sure if we can use this thermostat for this application...... I would have to do a little more research on this.
Expert:  Kcrand36 replied 9 months ago.
I will send you a link, and have you take a look at the wiring diagram, I think you will see why you are having a problem.
Customer: replied 9 months ago.
I'll send images of how the other one was hooked up to the old and how it's hooked up now, maybe that will help
Customer: replied 9 months ago.
Old
Customer: replied 9 months ago.
New
Customer: replied 9 months ago.
This is the one that works fine
Expert:  Kcrand36 replied 9 months ago.
https://customer.honeywell.com/resources/techlit/.../68.../68-0101.pdf, page 17. Even though you didn't have a T-87 stat,
Expert:  Kcrand36 replied 9 months ago.
ok, I have a thought. I'm thinking of removing the jumper on the new stat subbase between r and rc...... then retry the stat.
Expert:  Kcrand36 replied 9 months ago.
I have to run..... I'm going to open this up, to other tech's, they will pick up where we left off..... Please don't respond to this as it will come back to my desk, but your question will be posted for the next tech to pick up.
Expert:  Kcrand36 replied 9 months ago.
has anyone gotten back to you yet?
Customer: replied 9 months ago.
No, but I had to leave that house to meet my movers anyway... Didn't get a chance to remove the jumper, and I couldn't get that link you sent to load either
Expert:  Kcrand36 replied 9 months ago.
ok, I will send a pdf of it. I had to take the son to work....... but anyway, what happens is one of those stats, the one with the five wires that were hooked up, is the controlling thermostat, it uses the O and B terminals to switch between heat and cool.
Customer: replied 9 months ago.
Ok, I take it the link is a wiring diagram then?
Expert:  Kcrand36 replied 9 months ago.
I think it's attached here...... although I can't see it.
Customer: replied 9 months ago.
This is what I'm looking at... What exactly does it mean?
Expert:  Kcrand36 replied 9 months ago.
basically in the old thermostat it had a switching mechanism, it had like a two pole switch, when you put your thermostat in heat, it made a separate set of contacts close and energize that circuit.... if you set it to cool, it made a energized two different sets of contacts. Let me read a couple things and see if we can use these stats for this application. Can you take a picture of how you wired the other thermostat, just so I can make sure I have the whole picture.
Customer: replied 9 months ago.
Thought I sent those, I'll resend... These are of the thermostat that is working fine without the other attached
Customer: replied 9 months ago.
This is the old, and by the way the new one that is working worked fine with the old one hooked up that is the one messing up now with the new one installed
Customer: replied 9 months ago.
New one that works
Expert:  Kcrand36 replied 9 months ago.
one of the thermostats has to be the controlling thermostat..... In other words, did you have one stat in the say the cool position and if the other stat was not in the cool position it wouldn't work?
Expert:  Kcrand36 replied 9 months ago.
when you say the one thermostat that works, does it turn on the heat, and turn on the cool when set to operate?
Customer: replied 9 months ago.
It worked with the old thermostat, I haven't let it boot completely back up with the other new one because when I turn the system on the one that was working starts to boot up but the other that I just hooked up flashes Honeywell then goes blank and keeps doing it... And everytime it tries to restart the furnace makes a buzzing noise
Customer: replied 9 months ago.
I'm headed back to that house now, should I try removing the jumper first?
Expert:  Kcrand36 replied 9 months ago.
yes, because I think you are sending power through wrong terminals. I honestly don't think you can use these thermostats without a isolating switch to go from HEAT/OFF/COOL. They do have them, but you may need to get a tech in there to install it properly.
Expert:  Kcrand36 replied 9 months ago.
I cannot get any "real" installation instructions on the net. For those stats, they just don't have it easily available
Customer: replied 9 months ago.
Without the jumper it doesn't turn on at all
Expert:  Kcrand36 replied 9 months ago.
its the problem with the o and b terminals on this stat. It's not set up to do what you want it to do.
Customer: replied 9 months ago.
Ok, I'll just have to call someone to install it professionally then?
Expert:  Kcrand36 replied 9 months ago.
If I were you, I would call Honeywell first to walk them through, what you have. Make sure you have the model number of the zone panel, the model number of the old thermostats and the new thermostats. If they say you can't use those stats, I would say, how about if I upgrade the zone panel. I think it might actually be a good idea to do that. It looks like you have enough wires on each stat to do that.
Customer: replied 9 months ago.
Ok, thank you for your help. I appreciate it
Expert:  Kcrand36 replied 9 months ago.
You are very welcome. I'm sorry we couldn't get it working for you. If you could before you log off, leave a rating for the service. Thank you for using JA. Kevin

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