Connecticut Zone Control

Discussion in 'General Discussions' started by xSpecBx, Nov 14, 2021.

  1. xSpecBx

    xSpecBx New Member

    I live in SE CT and have a 4 ton hydron module Revolution 2 dual stage heat pump servicing 2 separate zones in my house (1st and 2nd floor). Zone controller is a honeywell HZ432 with honeywell T9 thermostats. Supplemental heat is 10kW heat strip. This system was installed in May so I'm heading into my first winter with the unit.

    Looking for some advice on the best way to setup the zone controller for efficiency and life of the equipment. My contractor setup the controller so that, if one zone calls it uses stage 1, but if both zones are calling than it will kick into stage 2. I've read others say they only go into stage 2 after some preset time if stage 1 can't handle the load and wonder if this would be a better configuration, and if so, what makes sense for the timer settings. The HZ432 lets you set a timer from 5-60 minutes in 5 minute increments to delay going into stage 2.

    My initial thought is that the timer method is better because, even if stage 1 runs for a little longer, it is better to run in the lower stage longer than bump up to stage 2, especially in the shoulder months when its not cold enough to work the heat pump that hard. I was thinking something like

    My contractor also had stage 3 (supplemental heat I presume) set up to be called by the thermostat, which seems wrong. Its on a separate breaker, so it wouldn't kick on anyway, but seems like you would want the supplemental heat to turn on after some extended period of time after stage 2 has had a chance to run and isn't able to handle the heating load.

    In stage 1, the unit puts out 75% of the blower capacity and stage 2 bumps it up to 100%. My initial thought is to set a 15 or 20 minute timer for stage 2 to kick in and set a 60 minute timer for stage 3 to kick in.

    Appreciate any input the smart people here may have. Thank you
     
  2. geoxne

    geoxne Active Member Forum Leader

    I use the Honeywell HZ432 on all my zoned geo systems. I prefer Honeywell TH8321R with Redlink thermostats. Together I can setup and configure to optimize staging in almost any scenario. I assume you can setup your T9's in a similar fashion but I am not familiar. I usually avoid the delayed TIMER setting because a delayed call is not based on what the zone needs and this delay is induced on every cycle.

    I usually setup the HZ432 zone panel to stage based on TSTAT signals (with some exceptions). My thought is the thermostat knows best what the zone needs and is "smarter" than the zone panel. Then I can setup the thermostat to stage based on zone requirements, efficiency and occupant preference.

    Typically, I set the thermostat Stage 2 to COMFORT. There is no great efficiency gain with avoiding 2nd stage geo HP's. The published COP's when comparing Stage 1 to Stage 2 are exaggerated by a 9F degree boost in EWT that doesn't happen in reality. It merely reflects efficiencies available during the shoulder seasons when full capacity is not required and the loopfield EWT is at a moderate temperature.

    3rd stage at the thermostat can be setup to your preference based on your system. I typically setup thermostat with a set DROOP in temp and/or TIMER. I have some clients that would rather die than turn on electric backup. They have the option of turning off the breaker until needed. I have others that have vacation homes that are unoccupied and require 3rd Stage in case of system failure while unoccupied to prevent freeze damage. They have to leave the breaker on. None the less the thermostat 3rd Stage is setup to their preference.

    The exceptions to 2nd Stage are related to individual zone requirements.
    -If there is a small zone than can not handle full air flow of 2nd Stage, I disconnect Y2 from that zone at the zone panel. That zone can never call 2nd Stage at the HP by itself.
    -If all zones are fairly equal in size but can not handle 2nd Stage air flow individually I set the zone panel to stage on %ZONES. In this case the zone panel will never call 2nd Stage unless 50% or more of the zones are calling. If you have only 2 zones you have to lie to the zone panel during setup and tell it you have 3 zones.

    Do NOT be confused by the DUAL FUEL setting. It means the refrigerant coil is down stream of the heating coil. Most typically seen with a forced air furnace. In this case the HP can not heat already hot air. The Dual Fuel setting will disabled HP operation when 3rd stage heat is calling. This setting should be ignored when 3rd Stage electric or HW coil is mounted AFTER the HP coil.

    Honeywell defines AUX HEAT and EMERGENCY HEAT differently because of this. AUX HEAT can run with the the HP. Conversely EMERGENCY HEAT disables HP heat (compressor operation). In most cases, where both are from the same source, a jumper wire is required between W1 and W3 on the Equipment terminals AND Thermostats side of the zone panel (as noted in zone panel wiring diagrams).
     
  3. xSpecBx

    xSpecBx New Member

    Thanks for the input.

    The thermostat you use is the one my installers recommended. I stuck with the T9 because I already had them and they have room sensors which I liked as it gave me greater flexibility with controlling room temperatures. Being a big box store type thermostat, it doesn’t appear to have the same level of control that you’re mentioning and looks like I could go up to the T10 and get that level of functionality.

    In regards to my efficiency comment, I wasn’t specifically concerned about heat pump performance, more energy usage. My zones don’t generally call at the same time, but it does happen frequently enough that I go into stage 2 for a couple minutes during the overlap. It seems particularly wasteful right now when temperatures are still pretty mild, using additional electricity and pulling additional heat from my ground loop when I could be operating in stage 1.

    I may just go buy a T10 so I can confirm if it has the controls you mention (the installation manual makes it appear that it does), otherwise, I think the only way to refine the stage usage and aux heat is through the zone controller using timer settings.

    Additionally, I don’t think my T9 thermostat will activate the heat strips in aux heat mode as intended, ie using them to boost the heat output, but will only turn them on as emergency heat when that mode is specifically selected. The manual for the T10 indicates it will activate the heat strips as they were intended so that may be the route I need to go. I don’t expect to need the heat strips, but want to make sure they operate correctly.

    Thanks.
     
  4. geoxne

    geoxne Active Member Forum Leader

    I assert what you perceive as "wasteful" is NOT. Yes, electric draw will increase momentarily but for a shorter period of time as your zones are satisfied more quickly. Wear and tear on the equipment should not be an issue with 2nd Stage operation. The compressor, blower, and pump are already spinning.

    I would not spend any $ until there is a real issue and a defined resolution. Your T9's may prove themselves more than adequate. If you are trying to optimize your system based on it's function during the shoulder season, you might inadvertently create delayed response issues when 2nd Stage is required as your heating load increases.

    Furthermore, your house needs a given amount heat to overcome losses. The ground loop is going to give up the same amount of extracted heat over time no matter what stage you are running during HP only operation.
     
  5. xSpecBx

    xSpecBx New Member

    Those are all good points and I have since put the system back to what they originally had (stage 1 when one zone calls and stage 2 when both zones call). Appreciate the thoughts. I tend to overthink these things sometimes so the pragmatic opinion is appreciated.

    I did go ahead and buy a T10 to check it out because I’m not convinced by anything I read that the T9 will engage the aux heat if needed. The T10 appears to have all the controls you mentioned in the one you recommended. The 9 and 10 appear to be interchangeable so swapping it out should be easy. If it does what I think than I’ll go ahead and buy a second one. We plan to put in a humidifier next year and would have needed to upgrade anyway, so not to worried about the sunk cost. Given what we spend on the system, a few hundred dollars for thermostats isn’t the end of the world.

    My biggest concern with the thermostats is making sure the system is functioning as intended and my wife doesn’t need to play around with anything.

    thanks again for the advice
     
  6. xSpecBx

    xSpecBx New Member

    Looks like the T9 thermostat works on the “comfort” setting , just doesn’t provide the customization that the pro level T10 does. The T9 also doesn’t have the humidifier controls, but it operates the aux heat as it would in the “comfort” setting on the T10. The T10 is much nicer as it lets you customize more settings as you mention above.
     

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