Ductless AC

A ductless A/C consists of two main components,  indoor unit ( also called fan coil) and outdoor unit ( also called condenser )

To start project, locate the right spot where the indoor unit can be installed.

  • A typical indoor unit is about 33" width x 12" height x 8" depth. (it varies a bit upon capacity of unit)

  • Indoor unit has to be 6" away from ceiling for better circulation of return air.

  • Indoor unit should be mounted high on wall since it blows air downward.

  • Lineset comes out of indoor unit and runs to outdoor unit.

  • Condensation tube comes out of indoor unit to drain condensation water. It only goes downward. ( If condensation tube has to go upward, a pump has to be installed )

  • Best spot is always on exterior wall since lineset and condensation tube can run through the wall to outside.

Locate the spot where outdoor unit can be installed. It should be close to indoor unit as much as possible because it will make lineset short. The shorter, the better.

  • Typical size of outdoor unit is 33"W x 24"H x 12"D. (it varies a bit upon capacity of unit)

  • The back of unit should be 4" away from wall.

  • The outdoor unit needs a plenty of air to exchange energy. It should be placed in open area.


The most important to be considered:

1. Inverter compressor

  • This is best technology. A bit more expensive than fixed speed compressor but it well worth the price

  • It automatically adjusts the output according weather condition.

  • It's more efficient and quieter


2. Efficiency

  • Rated as SEER (Seasonal Energy Efficiency Rating). The higher the number, the better

  • Typically start from 15 SEER


3. Sound Level

  • Indoor unit should be very quiet. Typically its sound level shouldn't be more than 55 dB at high speed.


4. Dehumidification

  • The indoor unit also functions as dehumidifier.

  • If outdoor unit is inverter compressor, the indoor unit will have longer cycle therefore it will enhance dehumidification


Facts related to installation

1. Power supply

  • Ductless A/C needs dedicated power wire. It can't share with other appliance.

  • It needs 220V directly from electrical panel. So panel should have two empty breakers for it.


2. Lineset

  • Lineset connects indoor unit and outdoor unit. It can't be more than 60 feet for most brands ( Mitsubishi Mr Slim can go up to 100 feet )


3. Condensation water

  • Since indoor unit functions as dehumidifier, there will be some condensation water coming out from indoor unit.

  • Best way is to drain condensation water by gravity like to mount indoor unit on exterior wall so that condensation water can be drained outside directly

  • To use pump to drain condensation water is not recommended since it makes noise and risks water leakage caused by pump failure


Most financially effective way of installing ductless air conditioner for house

  • To install a single head ductless air conditioner costs same level as central air conditioner

  • Even though there is dual-head or triple-head ductless air conditioner, the cost of that will be double or triple of the cost of single head.

  • To install a big capacity single head unit to cover the whole house is good tradeoff in affordability and performance. Below is picture showing that indoor unit is mounted on the wall next to stairs.