Outdoor condenser with basement air handler, that I can also add mini-splits to?

389 Views 6 Replies 3 Participants Last post by roughneck, May 5, 2020

tom_poconos

Discussion Starter · May 5, 2020 (Edited)

I have an old furnace/AC stack in my basement that I'm going to replace. What I would like is for the outdoor condenser unit to have the capability of supporting mini-split units in addition to the main AC coil in the basement. Is this possible? Would I need to get a condenser designed for mini-splits (like an LG multizone condenser), or could I just use a standard Goodman condenser and add a branch distribution unit in the future to support the mini-splits?

I'm wondering if this requirement is unusual and/or inefficient, and if it would just be better to add a second condenser outside if the need arose (I don't want to add window units).

Any advice would be appreciated.

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u3b3rg33k

· #2 · May 5, 2020

unusual setup for sure. You need to buy someones product and live with what they make as a kit/system.

the system you're asking for needs to be able to manage oil and refrigerant migration, be able to pump down the indoor units that are not active, and so on. these systems exist, usually in hotels/large buildings.

if you want to go this route, I think you'd be better off with one of those self-contained chilled water systems. then you just plumb pipes to each unit and fill it up, and the outdoor unit modulates to provide water at whatever temperature/volume is needed. Chiltrix makes one, I'm sure there are others.

if you're wanting simultaneous heating and cooling (one zone heating while another is cooling) then you need an even more complex setup.

example:https://www.chiltrix.com
they have a multitude of indoor unit styles to chose from, and you can feed a standard hydronic air handler as well. the outdoor unit will modulate the compressor to match demand between 25-100% of nameplate capacity.

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tom_poconos

Discussion Starter · #3 · May 5, 2020 (Edited)

u3b3rg33k said:
unusual setup for sure. You need to buy someones product and live with what they make as a kit/system.

I see, thanks.

You can buy mini-split systems with different sized indoor units, e.g 9+9+9+18, so I thought my idea was just a more extreme version of this - it would be something like 9+9+9+36, 36 being the basement coil (or maybe it's more like 48). In any case, they wouldn't all be on at once - the basement coil would be for daytime, and the mini-splits would be used at night. If this idea is crazy/dumb I guess I'll just put a small mini-split condenser on the roof for the upstairs rooms in the future.

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u3b3rg33k

· #4 · May 5, 2020 (Edited)

a multi-split works fine - it's a single-vendor product. I believe there are some that make an "air handler" style indoor unit but it would have to be part of their system.

I think mitsubishi makes them, you'll have to read through some spec sheets to make sure:
https://www.mitsubishicomfort.com/products/indoor-units/multi-position/compare

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roughneck

· #5 · May 5, 2020

No, minis can’t be mixed with other brands and/or styles of equipment.
They are proprietary.
It sounds like VRF would interest you.

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tom_poconos

Discussion Starter · #6 · May 5, 2020 (Edited)

roughneck said:
No, minis can’t be mixed with other brands and/or styles of equipment.
They are proprietary.
It sounds like VRF would interest you.

I guess I'm going to eventually have 2 cold-air systems then: 1) the whole-house ducted basement AC coil and 2) mini-splits from a rooftop condenser serving upstairs rooms. I remember roughneck you mentioned in a different thread that closing supplies to save energy was a bad idea as it increases static pressure in the system and puts strain on the equipment. What if in summer, I closed all the ducts to the upstairs, but opened an equal amount of additional "summer ducts" downstairs - would this theoretically solve the static pressure issue? I'm just trying to think of a way to make the whole-house basement AC coil just service downstairs (and faster) in the summer months, leaving upstairs just to the mini splits. Does that make sense?

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roughneck

· #7 · May 5, 2020

Doesn’t make a whole lot of sense, no.
You don’t want the space cooling down quickly.
As for the dampers, doing such a thing would likely cause parts of the house to starve for airflow.
You’d be best with multiple systems, a single zoned system, or as i mentioned before VRF.

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