|>|>| A well designed central system have few problems, likely fewer |>|>| than a number of single room systems. If you read here, you will |>|>| see the results of problem systems. We don't get questions about |>|>| well designed and installed systems. We get very few question |>|>| about the room units (as you are describing) but that is because |>|>| they are not common. |>|>
|>|> I would guess that the vast majority of installed central A/C are |>|> not properly designed and installed. |>| |>| Sad to say I agree. |>
|> And how much would it cost to get one to be well designed for 12 |> zones? |> This would have to be a design that sustains air flow in all zones. | | That would depend on the application.
A house where:
- Each major room has its own temperature setting, and if possible, a relative humidity or dew point setting. Major rooms are each bedroom, bathroom, kitchen, dining, living, great room, etc.
- Each room has selectable air flow that can be sustained even if that room is at desired temperature (e.g. closing a duct damper won't work).
|>|> I suspect that zoning by means of controlled air flow (e.g. shut off |>|> the air to rooms that are already sufficiently cool) is a culprit in |>|> A/C coils freezing up because the zone system sometimes runs too |>|> little |>|> air past. |>| |>| In a poorly designed system, yes. In a properly designed system |>| no. |>
|> The only zoning systems I have seen do it by shutting off air flow to |> the zones not to be cooled. And given that I will need at least 8 |> zones, possibly as many as 12, I suspect this will be a problem. | | Actually I have seen other systems. However what is possible or more | important practical depends on the particular application.
A house.
|> OTOH, zoning by means of several smaller "central" style A/C systems |> might still be feasible | | Yes, and maybe best, but always feasible.
So far I have not found such units small enough.
|> But one issue is that I need to have the air flow in each room whether |> or not that room needs a temperature change. If I use mini-splits in |> all the rooms, I'd still have the central air flow ducting in place |> with a passive blower. But I'd prefer connecting them together |> somehow |> if I can find a way, where the room unit has air fed from that central |> air flow system. |>
| | I am curious about why you want air flow to each room all the time. I | guess there are good reasons.
I don't necessarily want it all the time. I just want to be able to have it without being tied into heating/cooling. A typical one zone central system does have a fan auto/on switch. I often turn the fan on. But if it is a multiple zone system controlled by dampers shutting ducts off when that zone or room reaches desired temperature, then it cuts off the air there as well. I still want to get the air, but without the heat/cool. That would add more complexity to the system since now each zone will need to do a bypass, meaning a 2-way damper, separate blowers, times the number of zones (8-12). It would be a nightmare as a central system.
|>|> But I would never have a zoning system that is based on cutting air |>|> flow |>|> as the control means. So what else is there? |>| |>| So even if it were properly designed you would reject it? |>
|> Not necessarily. I'm just very skeptical that it can really happen. |> I'm not planning my house design around the prospect of a proper |> design being feasible. | | Sounds like a good plan. I suggest consulting with the professionals | before you finalize things, but there is plenty of time until then. Forming | a good idea of what results you want and what problems you have observed | elsewhere is a very good start. If it is your home, you should consider all | your concerns.
The air flow itself does not literally need to be centralized, either. Since the construction will be post-and-beam style, air ducts will need separate consideration. And so I do have to plan where those go as part of the whole layout. Adequate air flow would be less ducting than any central heating/cooling system would need, since it won't really need to go to the central location. Outside mix can be acquired in most rooms. Recirculation within the room would work in many cases. And maybe all I need are some good ceiling fans instead. Much is undecided.