Ductless Air Conditioning



Ductless air conditioning is available in such a wide variety of models that it should be easy to find a system that fits your home or office decor, and budget.


I've worked on many of them, mostly wall mount and ceiling mount models, and a few floor mounted units.


I've worked on units from Carrier, Daikin, Frigidaire, Westinghouse, Miller, Lennox, Sanyo, Mitsubishi, Trane, Toshiba, Fuji, York, and a number of other brands that I can't remember.


I can't recommend one brand over another, because I've seen low priced ductless air conditioning units run reliably for years, and I've seen high priced units with factory defects that made customers very unhappy.


My observation has been that if a new ductless air conditioning unit runs 24/7 for a week with no problems, it will usually run without problems for years.

That is, as long as it's kept clean, and not damaged by running it with low supply voltage or blocked air flow through the condenser or evaporator.


If there is a problem with the unit, it should show up within the first week, and definitely within the warranty period, so do your best to buy from a company that will honor the warranty.


If you're looking for a recommendation about buying ductless air conditioning, I always recommend buying the best unit possible from the nearest full service dealer.


What are the advantages of ductless air conditioning?


They are affordable and efficient, they can be installed almost anywhere in a building, and if you install several ductless units instead of one central air conditioner, you can cool individual rooms as needed, without having to run a large central air conditioner.


If you're a technician working on a ductless unit with an unusual problem, I know how you feel.


Do you have a newly installed system with low suction pressure, normal head pressure, low superheat, and the evaporator is freezing up?

I ask this question because this is a problem I've seen often with lower priced ductless air conditioning units.


Have you already replaced the orifice?

Or is it a cap tube system?

Have you verified that the condensing unit and evaporator are a matched set with regards to capacity?


You may have to install an evaporator pressure regulator in the suction line near the condenser.


Adjust the pressure at the inlet port of the EPR to the evaporator pressure you need.

It will prevent the freezing in the evaporator.

Check the pressure at the outlet port of the EPR (it will look low), and look for 20° to 30° superheat on the suction line 12" from the compressor.

You also want a normal 10° to 15° of subcooling.

The outlet of the EPR may frost and freeze, but if your superheat and subcooling are good, the compressor will be safe, and the unit will run and cool normally.


Are you working on a ductless air conditioning unit with an unusual electrical problem?


If you need a schematic, look on the inside of the cover panel of the evaporator unit, and also inside the cover plate of the electrical terminals of the condensing unit.

(I know you already have, but that is step one.)


Next, if the unit is a mass of wiring and solid state boards and the schematic is absolutely required, go to the manufacturers web site, and sort through it.

Some manufacturers have schematics available on line, some will send them to you after you contact them, and from some, I'm sure you already know, you don't get much help.


If you absolutely can't get the schematic, and have the parts available, re-wire the unit with normal everyday controls and a regular cooling thermostat.


I've done it several times under the following conditions:

The replacement boards were expensive and had to be ordered, with a delivery time so long that the customer didn't want to wait,

And, the customer wanted the air conditioning fixed now.


Keep in mind, you must explain this alternative to the customer clearly, be sure they understand, and it's a good idea to let them approve it with your employer over the phone.


If you do this, don't destroy the original boards as you remove them.

You may not be able to determine exactly what capacity run capacitor you need for the evaporator fan motor, and you may need to use the capacitor on the board.


Just another suggestion about a repair that has worked for me.


I hope this page has helped, and please, feel free to contact us with any specific HVAC questions you might have, including questions about air conditioning on Guam, or refrigeration on Guam.

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