14 Replies Latest reply: Jul 21, 2013 8:15 PM by therzog RSS

Nest and HZ432 zone panel

 fishtek New Nester

Hello,

 

I am in the process of building a new house, and have purchased 2 Nest 2nd gen Thermostats to use in the two zone house.  My HVAC (sub-contracted from our builder)  people have installed:

 

- Honeywell HZ432 Zone control board

- Trane xr95 furnace

- Trane xr13 heat pump

 

They are now telling me that in a previous house that had this same equipment they tried to get the Nest thermostats to work, and even called Nest Support, etc... all to no avail.  They eventually had to remove the Nests and install some honeywell thermostats.

 

I suppose the big compatibility question is more the Nest and the HZ432 (the other components are probably not in play?)?

 

Can anyone confirm if this equipment should be compatible with Nest?

 

I did a bit of digging and the best I can come up with is this post:

Re: How does the Nest control a 2-stage furnace? by Moderator-Eric where he mentions this link: http://support.nest.com/article/When-Nest-needs-a-common-C-wire

The follow up response to that post by bemyax mentions the HZ432 is a unit that should be added to the list of units at that link, that could need a common-C-wire.

 

Do you think that my HVAC folks simply didn't come across this information, and didn't attempt to run a common-C-wire?

 

Any information would be helpful!  Thanks,

ryan

  • Re: Nest and HZ432 zone panel
     bemyax Expert

    Hmm ... A 200-foot spool of 18/7 thermostat wire cost me $92US at Lowe's. Standard stuff in the back of an HVAC truck, I would think. Shucks, my 1989 furnace install got six wires!

     

    I don't have a link handy, yet the HZ432 installation instructions can be found on the internet. Read through them a couple of times, and perform an install. I don't see how it could be more simple and easy. Each of my Nests connected to the zone controller thinks it is hooked up to an HVAC unit. You have a dedicated transformer for the HZ432. I'm just a do-it-yourselfer, so I have no idea why you would ever want to leave out a common wire on new construction.

    • Re: Nest and HZ432 zone panel
       fishtek New Nester

      The HZ432 install guide is here:

      http://www.forwardthinking.honeywell.com/related_links/zoning/truezone/install/6 9_2070_01.pdf

       

      Yeah it seems like the common wire is something the Nest needs in a handful of different scenarios.  I'm just wondering if it isn't something that most other thermostats need?  And that possibly these HVAC people had never encountered this situation before and didn't properly diagnose the problem?

       

      One other variable is that there is a whole house humidifier installed as well (I don't have the model number, but can get it).  Everything I have read leads me to believe that Nest should have no issues controlling the humidifier as well.

       

      Could the humidifier have added extra complexity to the system or caused the incompatibility?  Or can you think of any other reason why these components wouldn't work with nest?

    • Re: Nest and HZ432 zone panel
       fishtek New Nester

      bemyax (or anyone else with this, or similar, zone control), do you have a duel fuel system (heat pump & furnace) or do you have just a heat pump.  Since I have a heat pump (XR13) and furnace (XR95) I'm guessing that the Duel Fuel (single stage furnace / single stage heat pump) wiring from the above HZ432 install guide should be followed?  Does that sound correct?

      • Re: Nest and HZ432 zone panel
         bemyax Expert

        No, I don't have a heat pump or dual fuel. Reading through the available information, it seems as though you are seeing the same logical path that I see. Something I'm not clear on is how one can bypass the use of outside temperature balance being provided by the HZ432, rather allowing Nest to perform that function by a call to the second stage. On the other hand, I've seen a serious advantage of being able to take staging decision making process away from Nest!

         

        As far as Nest being the problem point in the setup, I'd just wire W1 straight across. With this control board, Nest does not know it is not connected to the equipment. Anyone else out there with an HZ432 to dual fuel?

  • Re: Nest and HZ432 zone panel
     bemyax Expert

    Still wondering what decision points you came across in your setup and how you approached them. If the question about Nest/dual fuel/HZ432 ever comes up in casual conversation, I'd like to point them in the right direction.

    • Re: Nest and HZ432 zone panel
       fishtek New Nester

      Well I haven't arrived at anything yet.  The HVAC sub contractor was very against Nest when I spoke to them, and said they wouldn't be able to offer any sort of support if I had them put it in, so I had them put in "whatever thermostat they regularly use".  We don't close on the house for another 10 days, so I won't be able to "try out" the nests until then.

       

      However I did take a bunch of pictures of the thermostat's they hooked up, as well as how they wired the HZ432.  It sorta looks to me (and I'm curious of others opinions), like they wired it as a single stage heat pump?  So I'm thinking maybe if it is wired like they have it now, the HZ432 would handle all the decisions regarding when to enable the 2nd stages etc...?

       

      I'm attaching some of the pictures of the HZ432 and the two thermostat's they hooked up.  The downstairs thermostat seems overly simple, and I didn't even think a thermostat could work w/ only 3 wires?  The upstairs one looks a bit more "normal".  One other thing I noticed was the 2nd thermostat wiring on the HZ432 looks like they wired to the "L" wire, however I think (and I'll need to check for sure next time I'm there), that the wire itself is actually into the "O/B" line, and from the angle and the colored shielding just makes it look like it is into 'L".  So I guess I still have lots of questions, and if anyone knows the answers to any of them that would be great.  I'll update this thread when I actually get moved in and can do a bit of experimenting myself.

      IMG_4205.JPG.jpgIMG_4206.JPG.jpgIMG_4169.JPG.jpgIMG_4174.JPG.jpg

      • Re: Nest and HZ432 zone panel
         bemyax Expert

        Good pics. It looks like they left you in a good position to implement a Nest connection as a single stage heat pump, the HZ432 controlling which fuel to call. I'm guessing you can't tell Nest you have dual fuel because the two units would have to coordinate. I'm just dying to see how they hooked up the other side. (I reiterate, I'm just guessing.)

         

        Here's my both sides, each zone is the same as the others.

        IMG_20130605_213216.jpg

        IMG_20130605_213125.jpg

        • Re: Nest and HZ432 zone panel
           adw311 Explorer

          Hey Fish, I have a 3 zone setup with a carrier heat pump and air handler/furnace, controlled by a HZ322. I had trouble setting it up initially and I could not get heat pump balance because it thought it was dual fuel and not show heat pump balance. Then I read where the W/E (emergency heat) connection goes to the asterisk connection on the Nest and went through the pro setup then it saw everything correctly. Here are the pics of the original connections, controller and how I wired my nest. All three thermostats were wired the same.IMG_3469.JPG.jpg IMG_5794.JPG.jpg

          IMG_5797.JPG.jpg

          • Re: Nest and HZ432 zone panel
             fishtek New Nester

            bemyax, & adw311 thanks so much for the pics and advice!  Here are the pics from the other side of my HZ432. 

             

            I agree with you guys, that wiring and configuring the Nests for heat pump makes the most sense.  It is helpful to see that adw311 wired from the W1/E to the Asterisk on Nest.  Since adw311 has a w2 wire, I'm guessing that the two stage heat is controlled by the thermostat (which is your Nest now), and the stages are not controlled @ the zone controller, like in bemyax's case?  So in my case they only ran the W1/E line so it would seem that my zone controller is who is controlling the stages?

             

            So (and correct me if this seems wrong) in my case I'll wire from W1/E to the Asterisk and then I won't hook up anything to the W2, since my zone controller is already configured w/o a W2.

             

             

            IMG_4208.JPG.jpg

            IMG_4207.JPG.jpg

            • Re: Nest and HZ432 zone panel
               bemyax Expert

              a) You don't have an outside temperature sensor connected to allow the HZ432 to automagically transition between your heat sources. To me that would be ideal. b) We do not know if the HZ432 has a built-in protection preventing a call to the gas furnace and the heat pump at the same time! That would be if one Nest is calling for the heat pump and the other calling for emergency heat. You don't want that to happen.

               

              An example of built in protection is changeover delay. I left mine at twenty minutes. I can imagine some reckless teenagers coming into the house thinking, "Let's see what happens when we put two Nests on air conditioning and two Nests on heating!" (Or me, when I become more addled.) The point is that no Nest knows what the other is doing. Otherwise, you could go with a straight dual fuel setup like you would if you had only one zone and one thermostat.

              • Re: Nest and HZ432 zone panel
                 fishtek New Nester

                Good points for sure!  So I was just reading this thread, Nest 2 Install with Heat Pump w/Aux Heat - DoItYourself.com Community Forums, where someone has another similar scenario as mine (single wire that is labled AUX/E), and it looks like they have the option to wire to either the W2/AUX on the Nest or the * on the Nest.  The OP looks like he first used the * and then ultimately moved it over to the W2/AUX.

                 

                So I guess that is my dilemma is where do I run my "White W1/E" that is coming from the Zone Controller and currently is plugged into a AUX/E on my old thermostat...  My first thought would have been Nest's *, but now I'm thinking maybe W2/AUX?

            • Re: Nest and HZ432 zone panel
               adw311 Explorer

              fishtek, The way I understand it is your heat pump would provide your normal heating, unless it is too cold out. Your furnace would be your emergency heat. I didn't catch on that your furnace is gas, so in your case i think you would have a dual fuel setup and would use the W/E and W2. I am not sure on the 2nd stage heat if that is the setup you are going for. I believe my setup would be a "standard" heat pump split configuration. My air handler has the heat elements and would only be used as emergency heat, not a second stage. Hope this helps some. I am no professional .

              • Re: Nest and HZ432 zone panel
                 fishtek New Nester

                oh... also good points!  I am starting to see why the HVAC company had trouble getting it working!....

                 

                My zone controller doesn't have a W2 hooked up on the equipment side or the thermostat side, so I think my only decision is like i just mentioned above:

                 

                where do I run my "White W1/E" that is coming from the Zone Controller and currently is plugged into a AUX/E on my old thermostat...  My first thought would have been Nest's *, but now I'm thinking maybe W2/AUX?

                 

                And I guess which system type to choose...

                • Re: Nest and HZ432 zone panel
                   therzog New Nester

                  I have a very similar setup.  Two gen2, a 3-stage gas furnace and a 2-stage heat pump (Carrier in my case). The key here is to walk through the setup on the HZ432 to see how it is configured. Everything is pretty clearly described in the install guide.  It's true, a conventional stat, gen1 or gen2 Nest could control each zone just fine but it all depends which device you want to be the brain. Given so many installers inexperience with Nest, they fear what they don't know and tend to panic when pushed outside their comfort zone.  But to be fair unless you're willing to take on the burden of support, that's an understandable position.  For what it's worth I don't do this for a living and only have had to learn all of this because of my desire to use Nests with a dual-fuel/multi-zone setup.

                   

                  In your case the fact that you have zones, dampers and likely a bypass duct all complicate things. That's why you have a discharge air temp sensor connected (DATS) -- if only one zone is calling for cooling (and depending on how the zones are balanced for flow), some of the cool air is bypassed off the plenum and is returned almost directly into the coil giving a higher than normal chance of freezing. The DATS prevents this by either staging down or turning off the compressor while keeping the fan going.

                   

                  As mentioned, your nests think they are talking directly to the equipment. So they call for cool, heat or fan. Pretty basic. The HZ432 can be configured to handle staging by wht the thermostat calls for (not in your case based on the wiring), timers, or %zones.  It's probably just set to timers so that after a certain amount of time calling for heat (W1) or cool (Y1), the HZ432 ramps up the staging. And it determines which fuel to call for heat if configured correctly.

                   

                  The mention of an OAT sensor though is a missing component from your configuration. There is a point at which your fossil fuel heat will be more efficient that the heat pump (<40 or <45 degrees?) -- all depends on your home. The HZ432 can handle this info and again, it's all in the programming.

                   

                  Hope this helps. Bottom line... totally compatible. You only need 5 wires (R, C, Y1, W1, G) but can use as many as 8 (Y2, W2 and O/B) depending on how you want to configure. I'm unfamiliar why you would ever use the Aux connection.

                   

                  Good luck.