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Magic Boxes, wishful thinking or one stop shopping?

Wannabegreenbuilder | Posted in General Questions on

I, like many of you I suspect have hung off every word that GBA has written about these whole house air systems that provide us with clean air, remove contaminants, help control humidity, help us hang on to energy and repurpose energy already spent.   Yes, they sound almost too good to be true so of course I am instantly skeptical. They seem overly techy and with all the sensors and electronics might they have too many failure points and make homeowners wish they had adhered to the KISS system?  My hat is off to those brave people that plunged in first and bought these whole air systems with air source heat pumps built with them.  You folks are Beta testers and have my admiration.  I don’t have much contact with the European builders and their Magic Boxes but Minotair and Build Equinox systems seem to still be around in North America even after quite a number of years I have noticed.  It has been a long while since I first read reports of them on GBA and in other places.   I want to believe that they are the magic bullet/box I have been looking for and now that they have been around a number of years I would like to hear from you folks who I deem so much smarter than myself regarding  most things.   I am old enough to remember nay sayers that didn’t give the thumbs up to heat pumps when they started appearing in the residential HVAC market.  No one bats an eye if a home owner has a heat pump installed now.  I guess they stood the test of time.  What is your take on managing air/moisture/energy with a magic box?  Do you know anyone with actual experience with this technology?  How hard are they to service if they break down and do they break down often?   Is there anyone that is trained to service them.  What fails most often?  Is one model more delicate than another? Any info would be appreciated because I haven’t seen an update in a while and they do have some sort of track record by now.

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  1. Trevor_Lambert | | #1

    I've yet to see one of these units that can actually do more than one thing on its own, let alone do it all. The combination heat pump / ERV for example, take a look at the specs and compare that to your heating load. It's very unlikely it can supply all the heat, so you need a standalone heat pump anyway. So you end up paying 3-5 times the price for what is effectively a more efficient ERV. Then there's the question of how wise it is to tie up multiple functions in one device such that a single failure knocks out multiple functions. If you have a really well insulated house and your heat pump fails, the house can stay reasonably liveable for quite a while in a variety of conditions. If your ERV fails, you can crack some windows and your heat pump will continue to keep you warm or cool. If both functions get taken out at the same time, then opening windows in the middle of winter becomes a problem, as does leaving the windows closed with no powered ventilation.

    1. charlie_sullivan | | #2

      You say you are paying 3-5 times the price for a more efficient ERV. In fact, my reading of the data is that in many applications, these are less efficient than a regular ERV. In an ERV, the conditioning performed is accomplished for only the cost of the fan power. The all-in-one units I've seen don't have any such mode--they can only accomplish conditioning through the heat pump being active, and they lose the "magic" of a counterflow heat exchanger.

      So even though you are being critical, I think you are giving them too much benefit of the doubt.

      1. Trevor_Lambert | | #8

        The Minotair has an efficiency of something like 116%, per the standard test method for the HVI product listing. So regardless of the fact they're using a heat pump, the efficiency is indeed higher (at least at that one test condition). But when you consider that all that extra heating or cooling of the incoming air could otherwise be heated or cooled by a separate heat pump, then it's pretty pointless. So from the perspective of the overall house as a system, you're right, it is no more efficient.

    2. Wannabegreenbuilder | | #5

      I do have auxiliary heat. I am looking for efficiency, clean air and vapor control (to a lesser degree) in Montana (climate 6B) but you viewpoint does have some merit. When things break down here, it seems as though winter is when it occurs.

      Andy (Wannabegreenbuilder)

  2. Jon_R | | #3

    I'd analyze such devices from this perspective: for optimal comfort, health and efficiency, you want room-by-room control of temperature, ventilation and humidity, each one independently. How close are they to this? From what I've seen - not close at all.

  3. Expert Member
    RICHARD EVANS | | #4

    I don't disagree with the points brought up thus far but I will add that I am fascinated by these machines.

    The perfect home, in my mind would have the following components:

    Ducted heat pump
    centralized, dedicated de-humidifier
    Air purifier
    Balanced ventilation

    A magic box seeks to do all of these things in one unit. I know that the loads are quite small for heating/cooling but perhaps they do quite well as de-humidifiers and air purifiers? Although better than HRVs, ERVs do little to reduce indoor humidity- especially when latent loads are tiny in a super-insulated house and the AC running barely at all. The filter on my ERV does not eliminate odors from my neighbors wood stove, or potential VOCs within my home. A Magic Box might however?

    Its also worth noting that Magic boxes don't run continuously like ERVs. They pop on only when C02 or air pollution exceeds certain pre-set thresholds. At that point, the unit kicks on and blasts out the stale air to restore the interior conditions to more comfortable levels. The motors/fans are larger and more powerful and therefore less efficient than the tiny motors in an ERV. But, they may only run for a few minutes each day to meet the need. Because of this intermittent usage, they may actually use less energy despite not acting as a true heat/enthalpy recovery device and having less efficient/larger motors. (I'm speculating here...)

    I'm far from an expert on these things but believe that they might have a place in high-performance homes.

    1. Wannabegreenbuilder | | #6

      You sound like me! I want to believe they work but are they too good to be true? On paper they make a great deal of sense to me. Is this the future of air quality in tight homes of just a nice try? They have been around long enough surely some people have tested them and have first hand knowledge of performance, energy consumption and longevity by now?
      Andy (Wannabegreenbuilder)

      1. Trevor_Lambert | | #10

        None of that first hand experience is needed. All you need is the specs and some basic math to figure it out. No one using one of these has the ability to answer these questions based on real world experience. Let's say you have one, and also have an energy monitor. At the end of a year, you have detailed data on how much energy was used. Then what? What are you comparing it to? Unless you have an identical house right beside yours using alternate equipment (and an avatar who mimics your behaviour on a minute to minute basis), you're in no position to make any comparison. Sure, you could model the heating and cooling requirements and compare it to that. But that's more work and less accurate than just using the specifications and a hypothetical house.

    2. Trevor_Lambert | | #9

      "The filter on my ERV does not eliminate odors from my neighbors wood stove, or potential VOCs within my home. A Magic Box might however?"

      It might. Without evidence though, there isn't much reason to suspect that would be the case.

      "Its also worth noting that Magic boxes don't run continuously like ERVs. They pop on only when C02 or air pollution exceeds certain pre-set thresholds."

      I doubt this is how they actually operate. But if they did, it would be bad for several reasons. CO2 isn't the only contaminant, for one. I have my ERV set to boost if the CO2 goes above a threshold, but it still runs continuously at a lower level otherwise.

      "At that point, the unit kicks on and blasts out the stale air to restore the interior conditions to more comfortable levels. The motors/fans are larger and more powerful and therefore less efficient than the tiny motors in an ERV. But, they may only run for a few minutes each day to meet the need."

      I'd be surprised if they actually have significantly larger motors/fans. But even if they did, running a few minutes a day is not going to work, for heating/cooling or especially ventilation. Even in a super insulated house, in order to run for just a few minutes a day and cover the heat loss in winter, you would need something insanely massive, like hundreds of thousands (maybe millions) of BTU/hr. Then you'd get to deal with the massive temperature swings between each daily run cycle. Such a system would be less efficient than a smaller heat pump running most of the time as well. CO2 levels are even less compliant with such short run cycles. Even if you managed to completely change the air in the house in those few minutes (it would take a fan the size of another small house to do it; 10,000cfm wouldn't even come close), with an air tight house and no ventilation running, the CO2 levels are going to go over your threshold within a couple of hours at most. In reality, these all-in-one units have actually less heating capacity than even a small minisplit, and airflows in the same ball park as ERVs. The operating conditions you're speculating are pure fantasy.

      1. Expert Member
        RICHARD EVANS | | #11

        Ha! I'm certainly not suggesting that the intermittent use would apply to heating and cooling or even dehumidifing. Obviously that wouldn't work. It would need to run coninously to have the slightest chance of keeping up.

        I was referring to Co2 though. But you may be right- it likely would need to run more often than I stated to keep levels below 1000 ppm.

  4. ERIC WHETZEL | | #7

    Although it's arguably a more conservative approach, I agree with Trevor.

    Unless the homeowner/client has been educated about the risk --- the company could go out of business or just fail to respond to service requests if problems arise --- and agreed to face the potential financial consequences, it's probably wise to keep the functions separate.

    While working on a deep energy retrofit near me, I heard from two PHIUS-certified professionals that the Minotair is not 'plug and play'; that it's necessary to have a patient client who's willing to deal with what might be a prolonged commissioning period.

    It would probably help to have a motivated client with an engineering background who doesn't mind being on the phone with the company as they stand in front of the unit working through issues.

    You could contact this couple:

    They recently remodeled their suburban home and installed a CERV. I don't think they've been through all four seasons yet, but maybe they could tell you about their customer service experience so far. They're also in the same state as the manufacturer, so hopefully that helps should any issues come up (in terms of a timely response).

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