View Full Version : Ductless Ac Units
08-20-2005, 04:50 PM
I was just wondering about ductless AC systems, I have been a sevice tech for 20 years and now it seems that everyone one is making them now. Sanyo, Carrier, Mitsubishi, Samsung, Fujitsu, and now LG. Is there any real differance in them or are they all the same.
08-20-2005, 11:33 PM
I have installed 4 sanyo's this summer, they are very nice units. I was speaking to an owner of a 3 man shop the other day he averages 60 to 70 ductless installs a year He prefers SANYO, says they are the most reliable.
08-21-2005, 08:50 AM
i used to work in England and thats all they install there. The walls in old london buildings are too thick for ductwork (sometimes 3 feet of concreate). I installed about 100 and looked after at least 500. Mostly all Mitsibushi. And one system had 20 units to one outdoor unit - heat pumps one could cool the next could heat the next could cool. Varible speed compresssor too.
Another system had 30 units that you could control from a central control and they all had just 2 wires connecting each other by daisy chain. 2WIRES! i think they vary the frequency to control each of them. Compressor are VERY quiet and failures were low.
08-22-2005, 06:23 AM
sanyo and mitsi are the only two I insatll, and they have proven to be very reliable.
08-22-2005, 02:43 PM
I had a service call on a Fujitsu Heat pump.Drain clogged up .Anyways I do have a couple of questions.Should liquid line driers be installed on these units.Can these units be charged by superheat.What is the minumum lenghth of line set you can use.How and where do you measure subcooling.
08-22-2005, 07:31 PM
All I have installed (about60 units) were eather Mitsu"s or Sanyo's. I don't like working on Sanyo's. To hard to get to stuff. The other thing is I don't like embedded relays. I find Mitsu"s parts cheaper, price that is. As far as charging these units they are flooded evap coils so don't try to charge them at the piping connections. You need to remove the cover and go to the compressor. I've seen guys try to get good pressures at the piping connections and just about kill the unit. You also need to insulate both lines as they both are cold.
08-22-2005, 10:09 PM
On mini splits the small line is not a liquid line so I wouldn't use a drier there. They've got an expansion device in the out door section, so the small line is sending gas to the evap. The best thing to do is install and charge exactly as factory says in manuals. To check charge on a service call, I do use the compressor superheat method.I've seen them installed with rigid lines and filter/drier and sight glass setups on the small line and that is asking for an overcharge from a guy with less than good skills. I've used a suction filter/drier on compressor change outs and have had no problems with that. They can be rough on compressors up north in winter when used in computer rooms. They need low ambient control in that situation.
08-23-2005, 07:27 PM
NO. The small line is a liquid line. Think about it. These systems are just like walk in coolers. They flood the evap and will cycle on low pressure. The beauty of this is in a room whatever the unit temp is set for they won't freeze up like a dx will once the room temp gets below around 68degf. People in hotel rooms often sey the unit to it's lowest setting and go to town. I've never had a frezup on these systems. While they arn't very efficient (seer10)they don't cause problems. But because they are a flooded evap system charge checking can only be done at the compressor acess valves and from that point it's AC 101.
08-23-2005, 10:55 PM
Forgive me if I'm missing something,but the sanyo's and mitsu's I've seen have a cap tube after the condensor before the small ref. line. Does that not meen pressure has been reduced at that point? Not trying to be a smart ass, if I'm not right than I'm not right.
08-24-2005, 07:13 AM
I did come across one with a drier in the smaller line.It was insulated.Could this be a problem ?
08-24-2005, 09:28 AM
Ductless machiens are excellent for those tough areas or for computer rooms...The only thing is serviceing them 5-10 years down the road...Need to have alotta patients...Most of the pieces are plastic and like to break very easy if twisted the wrong way(blower mototrs)..I think they just came out with a mitsu that has one condensor that can do 14 evaporators...How technology is advancing :)
08-26-2005, 07:50 PM
No you're not missing anything except these systems arn't direct expansion systems they are flooded coils. These types of systems were normaly in walkin's except for the Westinghouse heat pump which also used a flooded coil. That allowed them to downsize the evap coil. Even though the coil is flooded metering still has to happen or the comperssor would eat it's valves. But just think what might happen with a dx system if someone set the t'stat to 50deg.
08-26-2005, 08:25 PM
to Hvacker, If I'm understanding what you're saying,are you saying that the refrigerant is lower pressure but still liquid. Also do you know of any links explaining the specifics of how ductless mini's work. I take care of a few and I'd like to understand them better.thanks in advance.
08-27-2005, 06:16 PM
Not sure where to look but it sure would be good for the industry if more info was available as these units are often overcharged when pressures are measured at the line connections.
08-27-2005, 07:42 PM
IMO all ductless are about the same we have plenty here in the island. My choice is McQuay for ductless this are very easy to service. Sanyo are good also but parts are to tight and there is no room to work.
08-28-2005, 11:47 AM
I came across one Unico system (high velocity ductless) it has some duct (flex) and an small airhandler that takes care of 3 or 4 rooms, kind of neat,they sell for about $16000 EA labor included.
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