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United States - US - Statue of Liberty - New Member

Join Date: Sep 2006
Posts: 81

Ductless Central Air?

05/11/2007 11:31 AM

I'm moving soon and looking around for apartments. In one of the apartments I looked at the landlady said she was going to be installing something called "ductless central air" soon. I was hoping some HVAC people would be able to share some information about what this is or if it's generally useful/efficient. I don't want to move in and find out that I have some inefficient, error prone air conditioning system that's going to send my electric bill through the roof. Thanks.

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Guru
Engineering Fields - Electrical Engineering - New Member

Join Date: Sep 2006
Location: El Lago, Texas, USA
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#1

Re: Ductless Central Air?

05/11/2007 1:25 PM

Using my awesome ability to type "ductless central air", I found:

http://www.healthgoods.com/Education/Healthy_Home_Information/Space_Heating_and_Cooling/ductless_ac.htm

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Active Contributor
Engineering Fields - Architectural Engineering - New Member

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Posts: 24
#2

Re: Ductless Central Air?

05/12/2007 12:26 AM

Ductless A/C units, also known as split A/C units, consist of two sections...a condenser located on the exterior and an evaporator section on the inside. It is similar to a thru-the-wall unit except that there is no wall penetration except for the refrigeration lines and some wiring for power and control. Look at Mitsubishi (Mr Slim) for example. These are good units (expensive) but if there are physical restrictions to free air flow from room to room, they may not work as well as a ducted system, as the ducts convey the cool air throughout the space.

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Anonymous Poster
#3

Re: Ductless Central Air?

05/12/2007 4:40 AM

Here is a website to a popular ductless a/c system. Operating expenses are comperable to a central A/C system. The room unit should us less power than a furnance fan. The condensing unit will be the same as a standard central air system. They work ok for appartments. They are quieter than a window or through the wall unit because the compressor remains outside in the condensing unit.

link http://us.sanyo.com/industrial/HVAC/Wall_Mounted/AC/

Good luck

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Commentator

Join Date: Sep 2006
Location: Argentina
Posts: 59
#4

Re: Ductless Central Air?

05/12/2007 9:56 AM

I have ductless HVAC. They are very popular in Argentina.Summer temperature raises 42 ºC easily. Here the cost is about USD 350 per room. Each unit drain 800W per room when are cooling. If one system fail, all the others rooms keep having HVAC. Over roofs can see one compressor unit per room in the house. All our external units are toghether on one plane low roof and are not visible from floor level.

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Commentator
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#5

Re: Ductless Central Air?

05/12/2007 2:27 PM

Thanks guys, I actually didn't end up getting that particular apartment but your information was useful. Thanks!

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Anonymous Poster
#6

Re: Ductless Central Air?

05/12/2007 6:32 PM

So, let me see if I understand all this (although, without JR...'s question, I would never have known I wanted to know).

A ductless H/AC does/is/comprises/consitutes(?):

  • A (more or less) "central" type unit with output and return duct work (possibly plenum as well?) left off
  • Relies on convection and conduction, solely, in lieu of ductwork
  • Relies on temp. stratification and/or user-provided secondary fans (to ensure coldest-/warmest-air intake) to attain uniformity of space heating/cooling.
  • Could be prone to producing significant ambient-space temp. swings, depending on floor plan size and layout
  • Is not able to accomodate ambient-space temp. balancing (via dampering) except with passageway doors, if any
  • Is suitable for apartment landlord installation where:
    • There is not space--even living area space, or capital funding to accommodate ductwork
    • The increased utility cost over time, in exchange for lower initial and maintenance (of-ductwork) cost, will be borne by others such as tenants
  • Is best suited for owner personal (or rent payer's) use where/as floor plan areas and obstructions such as walls, if any, are kept to a minumum
  • Is a system that would, for a prospective tenant seeking a multi-room flat-type apt. in a multi-unit, multi-building facility, be the next most economical (in succession) to:
    • a ducted system, which in turn is the next most economical to:
    • a central-plant, ducted system with submetering...next...and best...
    • the landlord assuming utility/fuel expense without raising rents

It would seem that, depending on who pays, the ductless system yields a benefits/anti-benefits trade-off, as between ducted-central-type and window/wall-type, respectively, in which:

  • cost and difficulty of installation (to the owner/landlord) is (usually) less with the former while greater with the latter, but...
  • as to cost of operation no benefit, or even a cost disadvantage, is to be (generally) anticipated for whomever pays.

Is this about it or did I overlook something?

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Guru
Engineering Fields - Electrical Engineering - New Member

Join Date: Sep 2006
Location: El Lago, Texas, USA
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#8
In reply to #6

Re: Ductless Central Air?

05/14/2007 2:05 PM

I think you missed it. Ductless A/C distributes the cooling fluid to remote fan units, instead of distributing cold air.

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Anonymous Poster
#9
In reply to #8

Re: Ductless Central Air?

05/14/2007 5:25 PM

Oh, I see. The refrigerant, not the air, passes through ducts (of a sort). And the fans move air over the fluid ducts to draw out heat? I was beginning to wonder why anyone--especially a landlord--might want a permanent A/C of the same type of which free-standing portables are readily available. So, in essence, you are talking about a kind of central plant (i.e., exchanger) set-up, on a small scale? Thanks, that changes everything. (Ps: Could this be applied over multiple dwelling units? If so, could it be feasibly metered amongst those units? Thanks again.

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Guru
Engineering Fields - Electrical Engineering - New Member

Join Date: Sep 2006
Location: El Lago, Texas, USA
Posts: 2639
Good Answers: 65
#10
In reply to #9

Re: Ductless Central Air?

05/15/2007 10:22 AM

I'd think it could be applied over a whole apartment complex - like the old style steam pipes that carried heat to radiators in each room.

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Power-User

Join Date: Jul 2006
Location: Houston, Texas USA
Posts: 171
Good Answers: 2
#7

Re: Ductless Central Air?

05/14/2007 11:23 AM

I installed a 3/4 ton unit to cool/heat the "jam room" I built in my detached garage. I didn't want extend the duct from my home's central air and I didn't want to cut a big hole that would let my loud guitar playing out. The split system was the perfect choice. It required only a 2.5" hole in the wall for the power line, the two copper tubes, and the condensation drain. As it turned out, I could have gone with a 1.5" hole because the unit doesn't cycle long enough to create condensate--a 1/4 ton would have been about right, but they don't come that small. I bought it on Ebay for about $735 total with all tubing, etc. I installed it myself in about 2 hours. The compressor/condenser unit came precharged. The evaporator/fan/control unit is about the size of a flattened big city Sunday paper and hangs on the wall like a picture. If I decide to enclose an additional area outside the jam room, I merely need to add another evaporator unit to the existing Condenser.

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Anonymous Poster
#11

Re: Ductless Central Air?

05/17/2007 6:10 PM

If you're looking for efficiency try (SEER 10), is a conventional efficiency for that equipment, remember that SEER (seasonal energy efficiency ratio) measures how efficiently a residential central cooling system (air conditioner or heat pump) will operate over an entire cooling season, as opposed to a single outdoor temperature. SEER is calculated based on the total amount of cooling (in Btu) the system will provide over the entire season divided by the total number of watt-hours it will consume:

SEER: seasonal Btu of cooling / seasonal watt-hours used

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Andy D/PE (1); Anonymous Poster (4); bhankiii (3); JRocket (1); Langdom (1); texlex (1)

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