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Controller to centralize control for heat and AC

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Setup: The home uses forced hot water banister heat that has five zones. Each zone has its own thermostat with independent pumps run by the zone controller on the boiler. I have five thermostats for heat, all of this works fine. The home also has three independent HVAC systems for AC. To complicate the conversation, each HVAC system also has electric heat elements just in case there is a critical failure to the boiler. The goal is not to use the electric heat unless it is an emergency. Each HVAC system has its own thermostat. To summarize, to control heat, there are five thermostats, one for each zone in the house. To control AC, there are three thermostats, one for each HVAC system. In total, there are eight wired thermostats in the house.

The problem: The house is now a vacation rental and explaining the heat and AC is difficult at best. For a homeowner, you know to run heat when you need heat, or run AC when you need AC. Unfortunately, this is not as simple to explain to people who are just staying for a weekend and really don’t care. The result, we come in to reset the house and find the heat and AC both running.

I am looking for a solution that will provide centralized control for both the heat and AC with a single digital controller located at one location. Since there are eight (8) wired controllers in the system (5 heat and 3 AC). I would imagine that each existing thermostat will need to be replaced with something that will wirelessly communicate with the single controller. I don’t necessarily need the controller to change from heat to AC to meet a specific temperature as much as I need a controller that will let you have either the heat on, or the AC on, but not allow both to be on at the same time.

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 23,323
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    And it may be that the whole thing is more complicated by the electric heat elements in the AC units? How are they controlled?

    I'm not sure however that wireless control is needed, at least for the heat, since you already have nice reliable hard wired signals coming together at the boiler. Something to said for that. If you could run similar signal wires from the three AC thermostats to the same location -- which presumably would have three signal wires each; common and heat command and cool command -- you would have all the information you needed in one place.

    I'm an old fogy, so if I were to do it I'd set it up with relays. But I daresay there's someone out there who could set up a small computer and interface arrangement to do the logic more elegantly, if not necessarily more reliably.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • exqheat
    exqheat Member Posts: 185
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    Simply I would look at the Honeywell 8000 Thermostat with redlink WIFI. You can control each thermostat on a central redlink ap showing all stats. The 8000 is progrsamable and can be locked. I love them.
    John Cockerill Exquisite Heat www.exqheat.com Precisions boiler control from indoor reset.
  • pecmsg
    pecmsg Member Posts: 4,861
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    Manually shut off the strip heaters unless needed!
  • 109A_5
    109A_5 Member Posts: 1,385
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    Hello @mnicholas,

    Interrupting (selectively disabling) the heating functionality of the AC system probably is not that hard.

    The hard part is detecting the Boiler failure, and then switching the Heating functionality of the AC to bring the living space to normal temperatures without the 'New' controller thinking the boiler is working again and disabling the AC heat function or maintaining a lower 'emergency' temperature.

    Then once the boiler is repaired is it a manual reset to disable the AC system's heating functionality until the next emergency ?

    And then what about any temperature setbacks during non-use times.

    It could be done with dedicated thermostat and relays that detects the loss of boiler heat and then 'latches' on the AC heating functionality. Or a PLC (Programmable Logic Controller) or PLR (Programmable Logic Relay) with a temperature sensing device.

    I'm not sure the Honeywell 8000 will do all those zones with that many heating / cooling units and the emergency heat logic mixed in also. To me the brochure got kind of vague there. With multiple Honeywell 8000 units, it may give you remote control so you can do the cut-over manually and remotely if there is 24/7 internet there.


    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • JMWHVAC
    JMWHVAC Member Posts: 32
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    As exqheat said, wifi stats would be neat and then you can control them remotely. If all you want is to prevent heat and AC fighting between themselves, a simple electronic temperature control can give you a warm weather shutdown for heat and possibly a cold weather shutdown for AC. That's something I have done for houses that otherwise have the capability to both run at same time.
  • ratio
    ratio Member Posts: 3,627
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    I think the Honeywell 8000 plan was a stat per zone, possibly 5 heat/cool & two heat only. Expensive (those stats are 150-250 each depending on the model), but the more hands-off the solution is the more it's going to cost.

    Just FYI, the 8000 stats are available as WiFi or RedLINK—not both; however, there is a RedLINK router that will get at most four RedLINK stats on the interwebz. You can have (nearly) as many stats under a Honeywell account as you want, though; I know of several sites with 20+ stats. The reason why this is important is because the RedLINK stats can use wireless remote sensors while the WiFi version can only use wired remote temp sensors.

    In case you can't tell, I like the Honeywell stats as well. They would be my go-to, middle-of-the-line solution, with a box of relays my low-end solution & BACnet or a PLC my high-end solution.

  • HVACNUT
    HVACNUT Member Posts: 5,841
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    Ideally you want an interlock to prevent heat and AC at the same time. That can be (MacGyverly) done remotely using a mobile app, but can easily be bypassed locally. Unless you use room sensors instead of accessible thermostats, or lockout the thermostats. That would of course require WiFi thermostats, which in turn requires 24 volts constant power that the heat only thermostats probably don't currently have.
    Control wiring and relays is the only sure way to provide an interlock. 
    The easy way is labels. I service many rentals and everything has a label.
  • mnicholas
    mnicholas Member Posts: 5
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    And it may be that the whole thing is more complicated by the electric heat elements in the AC units? How are they controlled?

    The HVAC systems have AC and Heat, so each HVAC thermostat can be placed in Cool / Off / Heat.

  • mnicholas
    mnicholas Member Posts: 5
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    ratio said:

    Just FYI, the 8000 stats are available as WiFi or RedLINK—not both; however, there is a RedLINK router that will get at most four RedLINK stats on the interwebz. You can have (nearly) as many stats under a Honeywell account as you want, though; I know of several sites with 20+ stats. The reason why this is important is because the RedLINK stats can use wireless remote sensors while the WiFi version can only use wired remote temp sensors.

    In case you can't tell, I like the Honeywell stats as well. They would be my go-to, middle-of-the-line solution, with a box of relays my low-end solution & BACnet or a PLC my high-end solution.

    Thanks for that little tidbit on the WiFi vs RedLINK.
  • mnicholas
    mnicholas Member Posts: 5
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    HVACNUT said:

    The easy way is labels. I service many rentals and everything has a label.

    That is our current solution. A small placard by each thermostat. They Say "I am for Heat" or "I am for AC". We also include an explanation in the check-in process. That doesn't stop the phone calls or messages asking how to control the heat / AC. At least every other week I get "There is no heat coming out of the vents". I guess people are not use to having a boiler.
  • mnicholas
    mnicholas Member Posts: 5
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    109A_5 said:

    The hard part is detecting the Boiler failure, and then switching the Heating functionality of the AC to bring the living space to normal temperatures without the 'New' controller thinking the boiler is working again and disabling the AC heat function or maintaining a lower 'emergency' temperature.

    I think notification settings for low temperatures in the home can resolve this outside of the overall solution. This past winter, I used basic home automation to send temperature notices out for low temps. I can easily go to the house and turn on emergency heat if I know something is wrong.
  • 109A_5
    109A_5 Member Posts: 1,385
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    Hello @mnicholas,
    OK maybe I misunderstood the situation. If you have access to the wiring and/or control, maybe just make the two basic systems AC / Boiler mutually exclusive, so only one can be used at a time.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • ratio
    ratio Member Posts: 3,627
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    mnicholas said:

    109A_5 said:

    The hard part is detecting the Boiler failure, and then switching the Heating functionality of the AC to bring the living space to normal temperatures without the 'New' controller thinking the boiler is working again and disabling the AC heat function or maintaining a lower 'emergency' temperature.

    I think notification settings for low temperatures in the home can resolve this outside of the overall solution. This past winter, I used basic home automation to send temperature notices out for low temps. I can easily go to the house and turn on emergency heat if I know something is wrong.
    The Honeywell app can send out-of-range emails for temp & humidity…

    Also, if you go with an equipment interface module (wireless unit control module [but the stat still needs 24VAC power]), you have IIRC three universal inputs that can be programmed for contact closure & custom text.

    It's dependable enough if you're near enough to check on things yourself, but I wouldn't depend on it alone if I were out of the state or something.