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problems with Mitsubishi split system
Bill_in_Delaware
Member Posts: 5
I have a Mitsubishi eight zone system (MXZ-8B48NA, I believe) in
my Cape Cod (about 1300 sq feet between the first and second floor and another
800 square feet in the basement). Seven
of the eight zones are connected and in use.
The system was installed in April 2012, replacing several room air
conditioners. The summer of 2012 and
the first half of the summer of 2013 were wonderful. I was never more comfortable. I kept the units on the first and second
floor set at 68 degrees and the unit in the basement set at 66 degrees. The air in the house was crisp and cool. The basement was cool and dry. Condensate poured from all the drains on the
individual units. At night, I closed the
master bedroom door a few hours before going to bed and turned the temperature
down to 59 degrees. The unit kicked up
to high speed with both green lights on .
By the time I went to bed, the temperature was down to 59 degrees and
the unit had gone back to low speed operation with just one green light
on. In the morning, I turned the
temperature back up to 68 degrees and opened the door. The compressor ran in single stage mode most
of the time, unless it was extremely hot.
Life was good!
Sometime about mid-summer last year, I came home and
realized that the temperature in the house was well above the set point. I called for service. The technician turned off the electricity to
the system, let it sit for several minutes and turned the electricity back
on. Once again, the air was cool and
shortly the temperature in the house was down to the set point. The technician checked the compressor and
said it was fine. I noticed in the days
that followed, the air in the house wasn’t as crisp as it had been although the
temperature was at the set point. The
air in the basement felt damp.
Condensate production stopped in most of the units and was greatly
decreased in the others.
I called for service again and was told that the air coming
out of the units was cold (about 59 degrees, I think) and the house was at set
point so there was nothing wrong with the system. I asked about the humidity and the lack of
condensate. I was told that split
systems don’t dehumidify as well as a Unico, for example. That didn’t explain why the system WAS
dehumidifying and doing a great job previously.
I ran the system in heat pump mode for a week or two in the
fall before I turned on my oil fired hot water baseboard, and again the spring,
after I turned off the hot water baseboard.
The system seemed to work fine.
This spring, I turned the air conditioning on and had the
same experience as the end of last year…
the house remained humid along with the basement; little condensate was
produced; and additionally, when I dropped the temperature down to 59 degrees
in the master bedroom, the unit stayed in high speed mode (both green lights)
all night. I bought a digital humidity
meter and found the house running close to sixty percent humidity.
I had my PM done in June.
The tech observed again that the temperature was at set point and that
split systems aren’t that good at dehumidifying. He cleaned the filters and the coils and put
a gauge on the compressor. He added some
refrigerant. The situation didn’t change
so he came back again. I had found an
oily spot on the branch box in the basement.
He said it was a refrigerant leak, tightened the fitting , and added
more refrigerant.
The situation isn’t any better. The humidity is running at 68-70
percent. The bedroom will only drop to
64 degrees at night even when it’s set at 59 degrees. The basement is really damp. Wet laundry hung up takes forever to dry, even
with a big fan running along with the basement unit set at 66 degrees. The compressor seems always to be in two stage
mode. I’d like to compare my electric
usage to last year, but we only went to smart meters in August of last year
from a system of estimated bills two months in a row followed by a bill based
on an actual meter reading. So, I don’t
have anything genuine to compare with right now.
The tech is coming back on Tuesday. I have faith in him. He’s a great guy and is knowledgeable about
AC, refrigeration, oil heat, gas heat, etc.
He’s been with the company a long time.
I just have the feeling something’s going on that he’s missing. Is it possible that the system is running
cold enough to produce cool air but not cold enough to condense the
humidity? If so, could that be caused by
something besides low refrigerant levels?
I’m looking for suggestions and insights. If I’m not satisfied after this visit, I’m
going to have to call the owner of the company, who, incidentally, sold me the
system. I feel like I’ve been really
patient, allowing time to see if additions of refrigerant helped the problem,
etc. Tell me what you think.
my Cape Cod (about 1300 sq feet between the first and second floor and another
800 square feet in the basement). Seven
of the eight zones are connected and in use.
The system was installed in April 2012, replacing several room air
conditioners. The summer of 2012 and
the first half of the summer of 2013 were wonderful. I was never more comfortable. I kept the units on the first and second
floor set at 68 degrees and the unit in the basement set at 66 degrees. The air in the house was crisp and cool. The basement was cool and dry. Condensate poured from all the drains on the
individual units. At night, I closed the
master bedroom door a few hours before going to bed and turned the temperature
down to 59 degrees. The unit kicked up
to high speed with both green lights on .
By the time I went to bed, the temperature was down to 59 degrees and
the unit had gone back to low speed operation with just one green light
on. In the morning, I turned the
temperature back up to 68 degrees and opened the door. The compressor ran in single stage mode most
of the time, unless it was extremely hot.
Life was good!
Sometime about mid-summer last year, I came home and
realized that the temperature in the house was well above the set point. I called for service. The technician turned off the electricity to
the system, let it sit for several minutes and turned the electricity back
on. Once again, the air was cool and
shortly the temperature in the house was down to the set point. The technician checked the compressor and
said it was fine. I noticed in the days
that followed, the air in the house wasn’t as crisp as it had been although the
temperature was at the set point. The
air in the basement felt damp.
Condensate production stopped in most of the units and was greatly
decreased in the others.
I called for service again and was told that the air coming
out of the units was cold (about 59 degrees, I think) and the house was at set
point so there was nothing wrong with the system. I asked about the humidity and the lack of
condensate. I was told that split
systems don’t dehumidify as well as a Unico, for example. That didn’t explain why the system WAS
dehumidifying and doing a great job previously.
I ran the system in heat pump mode for a week or two in the
fall before I turned on my oil fired hot water baseboard, and again the spring,
after I turned off the hot water baseboard.
The system seemed to work fine.
This spring, I turned the air conditioning on and had the
same experience as the end of last year…
the house remained humid along with the basement; little condensate was
produced; and additionally, when I dropped the temperature down to 59 degrees
in the master bedroom, the unit stayed in high speed mode (both green lights)
all night. I bought a digital humidity
meter and found the house running close to sixty percent humidity.
I had my PM done in June.
The tech observed again that the temperature was at set point and that
split systems aren’t that good at dehumidifying. He cleaned the filters and the coils and put
a gauge on the compressor. He added some
refrigerant. The situation didn’t change
so he came back again. I had found an
oily spot on the branch box in the basement.
He said it was a refrigerant leak, tightened the fitting , and added
more refrigerant.
The situation isn’t any better. The humidity is running at 68-70
percent. The bedroom will only drop to
64 degrees at night even when it’s set at 59 degrees. The basement is really damp. Wet laundry hung up takes forever to dry, even
with a big fan running along with the basement unit set at 66 degrees. The compressor seems always to be in two stage
mode. I’d like to compare my electric
usage to last year, but we only went to smart meters in August of last year
from a system of estimated bills two months in a row followed by a bill based
on an actual meter reading. So, I don’t
have anything genuine to compare with right now.
The tech is coming back on Tuesday. I have faith in him. He’s a great guy and is knowledgeable about
AC, refrigeration, oil heat, gas heat, etc.
He’s been with the company a long time.
I just have the feeling something’s going on that he’s missing. Is it possible that the system is running
cold enough to produce cool air but not cold enough to condense the
humidity? If so, could that be caused by
something besides low refrigerant levels?
I’m looking for suggestions and insights. If I’m not satisfied after this visit, I’m
going to have to call the owner of the company, who, incidentally, sold me the
system. I feel like I’ve been really
patient, allowing time to see if additions of refrigerant helped the problem,
etc. Tell me what you think.
0
Comments
-
Low on freon.
Most probably low on refrigerant. That oily spot he found would be a leak. The connection he tightened would likely be a flare connection. When a flare leaks, it is usually best to undo the connection, cut off the old flare and then re flare the pipe.
If this were me, I would first check every connection for a leak. Then I would recover the freon and see how much was left in the system. Then repair the leaks and weigh in the freon charge that was calculated by system design.
Harvey
1 -
Mini-split
If the system is cooling yet not dehumidifying, I would make absolutely certain that the indoor coils are very, very clean. These are not easy to keep clean due to their position in the head and the rather gimpy filters the factory provides.
Humidity comes from two sources: your lifestyle and your environment. Did something change in your daily life? For example, new house plants or another moisture source. Did something change in your house? For example, an opening to the outdoors of some type.0 -
Bad Info
Your tech has given you some bad info about the ability of the mini splits to dehumidify. They do an excellent job of dehumidifying - much better than ducted split systems. They are probably as good, maybe better, than high velocity (Unico, Spacepak) because of their ability to modulate.
I agree with Harvey and Spence that dirty evaporators and/or low charge are your two most likely issues.
Regarding charging your system: the ONLY proper method is to weigh in the TOTAL system charge. Harvey's spot on when he said the refrigerant charge should have been removed, the flare redone, the system leak tested, evacuated, the TOTAL system charge properly calculated and weighed in. That is the only correct method for charging a multi zone branch box system.
This ain't your grandpa's air conditioner. Things that are acceptable on a single stage ducted system may be totally wrong on this one.
One other note: setting the cooling to 59* inside is way below the system's design. It should not be set below 68* even though the control will allow it to go lower.Bob Boan
You can choose to do what you want, but you cannot choose the consequences.
1 -
Thanks!
Thanks to everyone for your replies. The tech came out yesterday to look at things. He'll be back tomorrow to take out all the refrigerant, leak-test the system, and recharge with the appropriate amount of refrigerant. Let's hope that takes care of things. Thanks again.
Bill0 -
Mitsubishi ductless-What a money pit!!! Good luck Bill. Sounds like the same scenario we have had since ours was installed in 2011. Our installer and different company we had to change to since installer couldn't find problem (all diamond dealers) still cannot find leaks. 15K to install and thousands of dollars later for leaking coolant plus labor charges for wild goose hunts of finding leaks on top of sky rocketing electric bills have all made us decide to cut our losses and have the thing de-installed and go with a different brand altogether. (Not ductless, thank you very much). Mitsubishi didn't care and the diamond dealer status they give installers did nothing for us. Mitsubishi will not back you or installers.
1 -
Cathi I'm sorry the Mitsu installers in your area are sub par. Finding a leak(s) can be a real pain, but it's not rocket science. That's a sad story.0
-
Oh yes that sounds very familiar. we have eight heads on a system and have had the same problems and more. It is a disaster. Mitsubishi has been no help.
0 -
Don't blame Mitsubishi their equipment is probably the best. It's the installer or the application.
Unfortunately this is what the HVAC world is coming to. In 10-15 years you won't find anyone who can fix anything. Big time "qualified" tech shortage
But like any manufacturer they probably don't insist on enough training. A chicken dinner and a beer doesn't make a technician0 -
Exactly why the installing contractor is more important then the name on the box.cathi said:Mitsubishi ductless-What a money pit!!! Good luck Bill. Sounds like the same scenario we have had since ours was installed in 2011. Our installer and different company we had to change to since installer couldn't find problem (all diamond dealers) still cannot find leaks. 15K to install and thousands of dollars later for leaking coolant plus labor charges for wild goose hunts of finding leaks on top of sky rocketing electric bills have all made us decide to cut our losses and have the thing de-installed and go with a different brand altogether. (Not ductless, thank you very much). Mitsubishi didn't care and the diamond dealer status they give installers did nothing for us. Mitsubishi will not back you or installers.
Most manufactures tech support will not deal with the end user. Your not the tech. There going to ask for specific data that the equipment owner will not have.0 -
Was there ever a resolution?? I am in the same situation. Getting nowhere with Mitsu or Installer.0
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Those of you having mini-split issues or problems finding leaks - do you have white insulation on your lines? Is so, you might find my post on lineset leaks helpful.
When I have mini-split issues and no diagnostic codes I usually pull out the charge and weigh it. More often than not, the charge is short.
Dirty evaps are getting to be a problem for us. Besides dirt balls coming out of the fan, some units will give you a freeze protection error in cooling and sometimes a high pressure lock out. Really hate cleaning them.0 -
These systems should be leaked checked at 400-500 psi as well...0
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I'm not sure about the residential units or the Mr. Slims, but the City Multis (big VRF systems) require a 650 lbs pressure test as part of the extended warranty procedure—no 650 lbs of N2, no extended warranty.
1 -
I tested all of mine at 650# of nitrogen.
This is what the tech should do if you have a leaker that is not found quickly - recover the refrigerant, pressurize system with nitrogen to manufacturer's recommendation, find leak, repair leak, evacuate, recharge.Steve Minnich
1
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