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Honeywell Prestige HD thermostat question...

Nifty thermostat, lots of control and retrofit possibilities via its many iterations, wireless options, etc. However, I don't see how this unit can be used to automatically accomodate hydronic heating systems that share a house with an AC system.

While the thermostat calls for heat just fine, there does not seem to be a way in its installer settings to select a hydronic heating / ac cooling system. As a result, every time heat is called, the thermostat will also energize the "G" terminal, turning on the fan. Now, having a fan running is not the end of the world, but it's also not necessary in the wintertime.

So besides manually turning the fan off (definitely an option), is there a way to get this thermostat to play nice with hydronic heating / AC cooling systems automatically? Is there perhaps a firmware update that addresses this issue?


  • Constantin
    Constantin Member Posts: 3,782
    edited October 2011
    Contacted Honeywell

    Per Honeywell, this model may only be installed by trained, licensed professionals. And these folk should have the answers I seek, even if they didn't, which is why I contacted Honeywell in the first place. The residential help line cannot help people like me because of liability reasons, or so they say. I wonder whose liability? Surely it can't be any liability regarding the use of a thermostat, since they'll happily support a customer on any other thermostat than the Prestige HD.

    They were nice enough to include a number for my HVAC professional to call them directly. But thankfully, I muddled until I found a way to support hydronic heat and a whole house humidifier and automatic changeover and so on is the following:

    Declare the system as a two-stage conventional heating system even if it only has one heating stage. Next, program the thermostat to only have the fan come on when it hits stage 2. Lastly, program the unit so that the fan comes on for the humidifier. Problem solved but not as intuitive as a "hydronic heat and AC" menu selection in the main setup menu, eh? :-D

    Anyhow, perhaps other thermostats have the same kinds of setup "tricks" to allow mixed heating and cooling system use.
  • Mac_R
    Mac_R Member Posts: 117
    Honeywell Prestige HD

    I love my HD stat.  Your problem is really simple to fix.  what you need to do is,

    1- touch menu

    2- go into dealer information and right down your date code.  it is a 4 digit code.

    3- go back into menu

    4- touch installer options

    5- view edit options

    6- system set up

    7- change oil gas heat to electric.

    8- touch back and save settings.

    that should take care of your problem.  you can run an installer test and see. 

    if that does do it you can use a jump drive and so a system back up.  just plug the drive into the bottom of the stat and go into advanced options and it will be listed there.  that way if you loose power and the backup battery is dead you can restore the settings.
  • Constantin
    Constantin Member Posts: 3,782
    edited November 2011

    I tried that approach initially and it didn't work on all of them (which in itself is weird, right?). The G wire kept getting energized on most thermostats whenever there was a call for heat.

    Setting the unit up for two stages works great since one can select that the fan doesn't come on (all of the thermostats were explicit about this) when on stage 1. That still allows the fan to turn on when there is a call for humidity.

    As for transferring installer settings, one interesting thing I discovered was that the XML file that is used to transfer those settings varies by firmware. Thus, one thermostat (older, newer? have to look at the mfg code) reported that its firmware was not compatible with the installer settings I had tried to transfer from another thermostat.

    Does Honeywell offer firmware upgrades to its installer base? I wonder since there doesn't seem to be a firmware upgrade button in the GUI, on the other hand, the thermostat auto-launches whenever a USB device is attached - i.e. it could autorun a payload at that point.

    Thanks again for the suggestions. I appreciated them.
  • ChasMan
    ChasMan Member Posts: 459
    Great Tip

    This is a great tip. I will try mine tonight. I am using the electric heat hack which works for me but the cycle timer seems to think that the electric heat has its own fan and even though the contact is not energized, it is including the run time in the fan cycle timer. But not the Air filter change reminder.

    Honeywell now has the Prestige II which includes a lot more Fan options. I don;t think I want to spend another 250 bucks just yet though. I'll wait for the one that has auto changeover of power between AC and Heat transformers depending on the Power status of said leg. Now that would be cool.. And a nicer wallpaper. One that is not so cloudy all the time. 
  • ChasMan
    ChasMan Member Posts: 459
    Prestige II

    The Prestige II has a setting for radiant heat. It also has a seperate ventilation menu and ventilation contacts. It looks like it might be the thermostat that the Prestige I should have been in the first place.

    Perhaps Santa will get me one. I tried the Heat has no fan in stage 1 deal and the circulation still doesn;t work right. It thinks that while the heat is on, that should count as fan on time even though it has no fan. This results in minimal if any circulation in heat mode.

    A big bug if you want circulation in the winter.

    After playing with the Prestige 2.0 demo, It appears that "Ventilation" and circulation are somewhat interchangeable if you set the ventilation type to passive fan only. And now the demo is stuck waiting for equipment in radiant heat mode.

  • Constantin
    Constantin Member Posts: 3,782
    Thing is...

    ... the only likely difference between the two models is a different firmware... so if Honeywell were to offer a firmware upgrade, that would be great - and a potential moneymaker for the trades also - "hey I can upgrade your tstat for $50...".

    But I'm not holding my breath for that to happen!
  • ChasMan
    ChasMan Member Posts: 459
    Back to single stage.

    I had to revert back to single stage. The main reason was that during recovery, the stat turns the second stage on so the fan runs constantly while the stat is in recovery.
  • Constantin
    Constantin Member Posts: 3,782
    Doesn't happen here...

    ... then again, there is no deep recovery going on. With a high-mass house, I didn't see the point. Plus, the small kids have us up at all hours, it's best to keep everyone comfortable while getting an AM snack.

    I wonder if, with enough research, one could decode/hack the contents of the XML file to figure out a way to allow a 1-stage radiant heating system + an AC system to co-exist peacefully on this Tstat. I guess the Prestige II has addressed this issue (good for them!) right out of the box. Who wants to volunteer to change the relevant settings a few times and download the XML settings each time to see what entries changed?

This discussion has been closed.