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  1. #1
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    Confused Honeywell TH8320WF1029 (VisionPRO Wi-Fi 8000) with Dual-Fuel (HP & Gas Furnace)

    Greetings. I am the home/equipment owner working with a licensed HVAC Contractor who suggested that I do this research. This is his first Dual Fuel install using the Honeywell TH8320WF1029 Wi-Fi VisionPRO 8000 Thermostat. This is not his first dual fuel install, but first with this Thermostat. I specified this Thermostat due to its Wi-Fi and Dual Fual capability. This is NOT a DIY post.

    Equipment: Rheem RPNL-031JAZ SS Heat Pump & Rheem R92PA070 SS NG Furnace. Thermostat has Outdoor Temp Sensor installed. System will be inspected and fired this coming Monday.

    Question 1: With the Honeywell TH8320WF1029, if the programming is as shown below, is it possible for the Heat Pump and Furnace to run at the same time?

    Question 2: Is setting 0360 ignored if 0200 is set to 1 (Fossil Fuel)?

    0170 = 7 (Heat Pump with Backup or Aux Heating)
    0200 = 1 (Fossil Fuel Backup Heat Source)
    0210 = 0 (No External Fossil Fuel Kit)
    0340 = 2 (Outdoor Temp Sensor set for Control)
    0350 = 40 (Compressor Lockout Temp)
    0360 = 45 (Aux Heat Lockout Temp)

    While programming the Thermostat, we both had concerns when we noticed that setting 0360 was even available after setting 0200 to 1 (Fossil Fuel). 0360 was not only available, but could not be disabled (set to 0), and required a setting 5 degrees higher or more than the setting in 0350. It was our understanding that with Fossil Fuel backup selected in 0200, that 0360 would (should) be unavailable, or irrelevant and ignored if available. A call to Honeywell did not provide answers to out questions, and with two different support techs later, we never got a definitive answer. They only suggested that the Thermostat may not be the right choice for the system. We were unable to get anybody on the phone at Honeywell that really knew anything about the Thermostat. Sad..

    Just for FYI, if 0200 is set to 0 (Electric Backup Heat Source), settings 0350 and 0360 can either be disabled, or set to practically any temp. But with 0200 set to 1 (Fossil Fuel Backup Heat Source), neither 0350 nor 0360 can be disabled, and both must be set, with 0360 required to be set 5 degrees higher (or more) than the 0350 setting.

    I hope I explained this clearly, and would greatly appreciate any experience here. The HVAC Contractor will not allow a Thermostat in the system that would allow the furnace to run at the same time as the Heat Pump, thus this research ahead if time. Obviously, we will be able to test this at some point, but it would be nice to know for sure, ahead of time, how it will operate. The Contractor has used the 8000 Pro series before (but not the Wi-Fi model), and with 0200 set to Fossil Fuel, 0360 doesn't even show up.

    Finally, these two statements are pasted directly from the Installation Manual for the Thermostat.

    Heat Pump Temperature Lockout (with fossil-fuel backup): If the thermostat is installed with an optional outdoor sensor, you can select a compressor lockout temperature (Function 0350). When the outdoor temperature is below the lockout temperature, only the auxiliary heat operates. When the outdoor temperature is above the lockout temperature, only the compressor operates.

    Heat Pump Temperature Lockouts (with electric heat backup): If the thermostat is installed with an optional outdoor sensor, you can select a compressor lockout temperature (Function 0350) and/or an auxiliary heat lockout temperature (Function 0360). When the outdoor temperature is above the auxiliary lockout temperature, only the compressor operates. If the outdoor temperature is between the compressor and auxiliary lockout temperatures, both the compressor and auxiliary heat can operate.

  2. #2
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    Dec 2005
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    In order:
    1. No. As long as 0200 is set to fossil fuel they shouldn't run together...UNLESS...the heat pump does send a furnace signal in during defrost and you may get a nuisance instance of this happening. For that reason on dual fuel I never connect the defrost wire.

    2. No, and in fact you want to make use of it. The entire idea behind dual fuel is to kick the gas in when the HP won't or can't comfortably heat. In my area (midwest) I set that 40 degrees for comfort reasons. You may have to play with that to find the point where savings and comfort cross.
    Good? Bad? I'm the guy with the gun.

    Statements made by me are strictly my opinions and do not reflect the opinions of my employer. I am not authorized to make any official statements on behalf of my employer.
    Any technical advice offered by me is for educational purposes only, all HVAC related repairs should only be attempted by qualified personnel.

  3. #3
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    Thread Starter
    The Contractor did not connect the defrost wire for the same reason you stated, although he stated that he has run furnaces during defrost before.

    His (and I suppose my) concern is high head pressure running the furnace with the heat pump. It appears that with the 5 degree spread between the compressor and aux heat lockouts, that the thermostat will allow it to happen. As the one paying the fuel bills, I'm not overly concerned about supplementing the heat pump when it gets to the point of barely maintaining temperature. I'd rather just rather burn the gas. When it warms up outside to the point that the heat pump will easily maintain, I'd rather the furnace just shut down. Is there a better thermostat that is Wi-Fi (or z-wave, etc.) capable that will do this? My desire for something remotely controllable stems from my long-term work travel that will begin in January. My Contractor is not up on connectivity. He has half a dozen other thermostats that will prevent both units from running at the same time, but none of them Wi-Fi.

    Just curious.. Even though I will run a Fossil Fuel backup, if setting 0200 was set to 0 (Electric Backup Heat Source), I could disable 0360 altogether and only use 0350. Do you think this would work, by lying to the Thermostat? Would it really matter?

  4. #4
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    what that means when you set 200 to fossil fuel except as mentioned above about defrost they will only run one or the other, not both. Lets say it's 43 outside a call for heat will start the heat pump unless temp drops below 40 or space is not heating up then the furnace will start and the heat pump will shut off. It will stay that way until either the heat call is satisfied or the outside temperature rises to 45. Personally I do hook up the defrost wire. It helps speed up the defrost, doesn't affect head pressure. I would set 350 to 30 degrees & 360 to 50 degrees

  5. #5
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    DO NOT set 0200 to electric. The stat's software, properly set up, will not allow both units to run at once for any amount of time that would cause damage. I've installed and set up a dozen or so of these and never had an issue. Just relax and trust Honeywell to know what they're doing.
    Good? Bad? I'm the guy with the gun.

    Statements made by me are strictly my opinions and do not reflect the opinions of my employer. I am not authorized to make any official statements on behalf of my employer.
    Any technical advice offered by me is for educational purposes only, all HVAC related repairs should only be attempted by qualified personnel.

  6. #6
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    just make sure the sensor wire is a seperate wire
    Go Trump

  7. #7
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    Thread Starter
    I think I am starting to get it. Thank you all for your answers.

    catmanacman, yes, a separate wire was used for the outdoor temp sensor.

    dougfamous, we're not going to set 0200 to electric. It was just an observation made concerning the flexibility of allowable settings between 0350 & 0360 in either mode. But after digesting what you guys have said, reading other posts, and re-reading everything in the Honeywell manuals, I'm starting to see the reasons for the differences in allowable settings at 0350 & 0360 for electric vs fossil fuel backup.

    superfittertech, thanks for the advice on settings and on the defrost consideration. I will discuss that with the HVAC Contractor tomorrow. The defrost wire could be easily connected. Also, when you stated, "or space is not heating up then the furnace will start and the heat pump will shut off", were you referring to the "droop" setting(s) [0347 & 0349]? I really did not consider that if the temperature drooped too much while running the heat pump that the furnace would kick in and the heat pump would shut off. I guess I reasoned that if 0350 was set to a point that the heat pump would be struggling to keep up, that it would just lock it out and rely on the furnace alone. If above that point, that the heat pump would just run 100% of the time. But that is not realistic if I plan to use setbacks while working or traveling. If 0360 is set too low, then I would be not be allowing the furnace to run in those times when recovering. Am I understanding this correctly?

    Can any of you elaborate on settings 0347 and 0349, specifically, what the difference is between "comfort" and "economy" for 0349, and how it may or may not affect 0347?

  8. #8
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    Quote Originally Posted by STRunner91 View Post
    While programming the Thermostat, we both had concerns when we noticed that setting 0360 was even available after setting 0200 to 1 (Fossil Fuel). 0360 was not only available, but could not be disabled (set to 0), and required a setting 5 degrees higher or more than the setting in 0350. It was our understanding that with Fossil Fuel backup selected in 0200, that 0360 would (should) be unavailable, or irrelevant and ignored if available. A call to Honeywell did not provide answers to out questions, and with two different support techs later, we never got a definitive answer. They only suggested that the Thermostat may not be the right choice for the system. We were unable to get anybody on the phone at Honeywell that really knew anything about the Thermostat. Sad..

    [/I]
    Maybe you understand this now, but I don't think it was explained to your specific question.

    350- keeps the heat pump from operating below the set temp, say 35

    360- keeps the furnace from operating above the set temp, say 50

    Between these 2 temps, 35-50, both will operate to maintain the desired temp. What the lockouts do is keep the unit from even trying to work, in that mode, because it is more efficient to work in the other. Below 35 the furnace is the better choice and above 50 the heat pump is the better choice.

    While these are generic temps and statements, the contractor should know this info, as well as Honeywell(sometimes they don't explain it well). The contractor needs to know this info, as well as the balance point, so he can set the stat up properly.
    The Food Stamp Program, administered by the U.S. Department of Agriculture, is proud to be distributing the greatest amount of free meals and stamps EVER.
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  9. #9
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    Thank you, pacnw. Makes sense.

    Quote Originally Posted by pacnw View Post
    ...Between these 2 temps, 35-50, both will operate to maintain the desired temp.
    From what I've gathered from this thread, my original concern of both units running at the same time seems to have been answered, but please indulge me once more. Using your example temp settings, even though both will be allowed to operate between 35-50, they will never be allowed to operate at the same time (except in defrost if the defrost wire is connected). Is this correct? No chance of high head pressure in the heat pump from furnace and heat pump running simultaneously, correct?

    I can't tell you folks how much this has helped. I truly appreciate your time. The Contractor does know this stuff, but typically uses other thermostats that are documented much better. This unit that I wanted lacks definitive detail concerning a few issues, so we wanted to be sure ahead of time. His installation is very impressive - Probably the neatest and most professionally done job I've ever seen. This will be my first experience with dual fuel heat. Can't wait to fire it up.

  10. #10
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    [QUOTE=STRunner91;19214041]Thank you, pacnw. Makes sense.



    From what I've gathered from this thread, my original concern of both units running at the same time seems to have been answered, but please indulge me once more. Using your example temp settings, even though both will be allowed to operate between 35-50, they will never be allowed to operate at the same time (except in defrost if the defrost wire is connected). Is this correct? No chance of high head pressure in the heat pump from furnace and heat pump running simultaneously, correct?


    Yes that is correct.

  11. #11
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    Thread Starter
    Perfect! Thank you. I think I'm going to like this thermostat.

  12. #12
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    Thread Starter
    Hi Folks. Just an update. While I greatly appreciate everyone's comments a few weeks ago when I started this thread, I have found that maybe some of the information wasn't based on fact.

    With the Honeywell TH8320WF1029 (VisionPRO Wi-Fi 8000) Thermostat, if Fossil Fuel Backup Heat Source is selected (0200 = 1), setting 0360, although present and adjustable, is disabled. Whatever you set in 0350 for the compressor lockout temperature, that is the only setting that matters. This thermostat ignores 0360, and if temp is above the compressor lockout temp, the furnace WILL NOT aid during droop or recovery from a planned set back.

    There is a few degree spread (maybe 2 or 3) from the 0350 lockout temp, in which the temperature has to rise above the compressor lockout temp for the furnace to be disabled and the heat pump allowed to operate again. For instance, with 0350 set to 40 degrees and as the temperature rose through 40, I noticed that the furnace kicked on with the outside temp at 42 degrees, but after it ran it's cycle, the next time the heat came on (around 43/44 degrees) it was heat pump only, and remained heat pump until the temp dropped below 40 the next night.

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