Mitsubishi mini-split problems

[MushCreek]

We have 2 Mits Hyperheat units in the house, and they are amazing, at least until one of them leaked down. A couple problems: There is a lot of corrosion, inside and out. I can't imagine what's causing it, as we are hundreds of miles from the coast. The line sets are green, and there is corrosion on the coils. The system is only 3 years old. The HVAC tech was surprised to see so much corrosion. Any thoughts? Also, we haven't found the leak yet. He recharged it, and the cooling performance dropped off in a week, so there's definitely a leak- somewhere. The units are so cramped it's hard to really check it. Haven't found any tell-tale oil yet.

Is it practical to service these units, or is it easier/cheaper to just replace the head unit (if that's the problem)? How much work to replace a coil, for example? I would normally do some of the work myself, then let the tech do the final servicing and charge, but I'm laid up for a bit, so I can only watch (and write checks).

Lastly, where does one order parts for these things? I know from prior experience that just letting the A/C guy supply them is usually the most expensive option. Thanks for any input!

 

[finn]

They are still under warranty if they are truly only three years old.

Let the hvac company that installed them either find and fix the leak, or replace the units.

Is the leaking refrigerant causing the green residue? Is the non-leaking unit “corroded” has too?

 

[tyme2par4]

I've heard that when freon and moisture mix they can cause corrosion on the copper. I would look in the most corroded location first.
Also when I had a leak in my system, the HVAC tech put some fluorescent dye in the lines. I was able to clearly see the leak after the system ran for a few days.

 

[turbowoodworker]

Those have a five to ten year warranty depending on who installed them (certified Mits installer=10 years).

 

[justinjoyal]

Have the hvac company/guy do the work. Should be under warranty.

Finding a leak is usually easy on a mini-split..

 

[TRWham]

Any chance the bad unit has been exposed to ammonia?

 

[eddieK]

We have 2 Mits Hyperheat units in the house, and they are amazing, at least until one of them leaked down. A couple problems: There is a lot of corrosion, inside and out. I can't imagine what's causing it, as we are hundreds of miles from the coast. The line sets are green, and there is corrosion on the coils. The system is only 3 years old. The HVAC tech was surprised to see so much corrosion. Any thoughts? Also, we haven't found the leak yet. He recharged it, and the cooling performance dropped off in a week, so there's definitely a leak- somewhere. The units are so cramped it's hard to really check it. Haven't found any tell-tale oil yet.

Is it practical to service these units, or is it easier/cheaper to just replace the head unit (if that's the problem)? How much work to replace a coil, for example? I would normally do some of the work myself, then let the tech do the final servicing and charge, but I'm laid up for a bit, so I can only watch (and write checks).

Lastly, where does one order parts for these things? I know from prior experience that just letting the A/C guy supply them is usually the most expensive option. Thanks for any input!

Calling for low temps with low ambient? Filters clogged...are both lines well insulated?

It sounds like it could be icing...

Because they update their units every couple years...its not always possible to just replace one of the two components.

 

[eddieK]

They are still under warranty if they are truly only three years old.

Let the hvac company that installed them either find and fix the leak, or replace the units.

Is the leaking refrigerant causing the green residue? Is the non-leaking unit “corroded” has too?

Warranty covers manufacturers defects...not leaks that are almost always at the connections. You need to have a nitrogen pressure test and locate the leak (s) ...in the end that is money well spent...if the leak is in the equipment, that should be covered by warranty. IF the unit was installed by a pro.

 

[MushCreek]

Not icing (I checked. Clean filters, lines very well insulated. It's leaking somewhere. Now the trick is to get the guy back out during a serious heatwave...

 

[eddieK]

Not icing (I checked. Clean filters, lines very well insulated. It's leaking somewhere. Now the trick is to get the guy back out during a serious heatwave...

Dont need high temps to find leaks...nitrogen test to higher pressure than system runs at high ambient.

Asking for low temps when ambient is too low causes icing and when charge is mid low it can happen. Corrosion is from moisture not refrigerant/oil.

 

[walta]

Chinese drywall?

http://chinesedrywall.com/index.html

 

[finn]

Warranty covers manufacturers defects...not leaks that are almost always at the connections. You need to have a nitrogen pressure test and locate the leak (s) ...in the end that is money well spent...if the leak is in the equipment, that should be covered by warranty. IF the unit was installed by a pro.

A reputable installer would cover leaks caused by his faulty installation.

At least the two I have used would.

 

[R.Anderson]

Not icing (I checked. Clean filters, lines very well insulated. It's leaking somewhere. Now the trick is to get the guy back out during a serious heatwave...

Sarcasm or are you serious?

 

[sms1974]

Chinese drywall?

http://chinesedrywall.com/index.html

The black oxidation is usually a sign of formicary corrosion, very common to have multiple leaks with that. Only real permanent fix there is replacement with an all aluminum coil

 

[R.Anderson]

We have 2 Mits Hyperheat units in the house, and they are amazing, at least until one of them leaked down. A couple problems: There is a lot of corrosion, inside and out. I can't imagine what's causing it, as we are hundreds of miles from the coast. The line sets are green, and there is corrosion on the coils. The system is only 3 years old. The HVAC tech was surprised to see so much corrosion. Any thoughts? Also, we haven't found the leak yet. He recharged it, and the cooling performance dropped off in a week, so there's definitely a leak- somewhere. The units are so cramped it's hard to really check it. Haven't found any tell-tale oil yet.

Is it practical to service these units, or is it easier/cheaper to just replace the head unit (if that's the problem)? How much work to replace a coil, for example? I would normally do some of the work myself, then let the tech do the final servicing and charge, but I'm laid up for a bit, so I can only watch (and write checks).

Lastly, where does one order parts for these things? I know from prior experience that just letting the A/C guy supply them is usually the most expensive option. Thanks for any input!

Few questions:


Was there any refrigerant left in the system to find a leak?
If not there may be contaminants in the system now after trying to find a leak. Hoping the tech at least threw gauges on before looking for a leak.

Did the "tech" recover (if needed) and do a pressure test prior to recharging?

Is this the outdoor unit or indoor unit or both with the corrosion?

With it leaking that fast the leak should be fairly easily to find.

Get some Nu-Calgon Blue Gas Leak Detector.

http://www.nucalgon.com/products/gas-leak-detectors/cal-blue-plus

The 7 oz. pressurized spray is the bee's Knees for tight cramped areas.


I personally would have a problem doing the "final servicing and proper charging" if some one else did the install. If I did I would be taking on the liability if the system leaks from a loose fitting, kinked line, or who know what.

Any chance the bad unit has been exposed to ammonia?

With that note and if it is the outdoor unit.
Do you have a pool or near one?
What about dogs?
Spray on fertilizer for the grass or gardens?
Run off from roof?
A neighbor that hates you?

Warranty covers manufacturers defects...not leaks that are almost always at the connections. You need to have a nitrogen pressure test and locate the leak (s) ...in the end that is money well spent...if the leak is in the equipment, that should be covered by warranty. IF the unit was installed by a pro.

With Mitsubishi they will cover parts but not labor if it ends up being a warranty issue.

A reputable installer would cover leaks caused by his faulty installation.
At least the two I have used would.

I agree 100%
I know we cover our own F-ups and have. Also some that were not that were manufacturing issues but no parts needed so no warranty. One the darn LEV coil popped off a day after install had to go out trouble shoot and fix. Drive time there and back was 2hrs. Ended up the wire harness was too tight and was pulling on the coil.

 

[MushCreek]

The point about the heat wave is that he is very busy. A/C guys are always slammed when it's hot out. His first visit was a quickie. I'm going to ask him if he really has time to properly diagnose this. Otherwise, I'm just wasting time and money.

As for the corrosion-

Outdoor unit is 4' off of the ground
No pool
American drywall (I checked)
Corroded about the same, inside and out, including the line set
That part of the yard doesn't get fertilizer
3' roof overhang, and I have gutters.

The only thing 'unusual' about our house is that it is ICF- concrete walls, encapsulated in foam. It took a LONG time for the humidity to come down once we started conditioning- I'm assuming because of all of the moisture in the concrete. Even now, the humidity runs about 50%.

 

[R.Anderson]

The point about the heat wave is that he is very busy. A/C guys are always slammed when it's hot out. His first visit was a quickie. I'm going to ask him if he really has time to properly diagnose this. Otherwise, I'm just wasting time and money.

As for the corrosion-

Outdoor unit is 4' off of the ground
No pool
American drywall (I checked)
Corroded about the same, inside and out, including the line set
That part of the yard doesn't get fertilizer
3' roof overhang, and I have gutters.

The only thing 'unusual' about our house is that it is ICF- concrete walls, encapsulated in foam. It took a LONG time for the humidity to come down once we started conditioning- I'm assuming because of all of the moisture in the concrete. Even now, the humidity runs about 50%.

Odd, by any chance you have copper pipes any where else in the house and are those corroding as well?

 

[eddieK]

A reputable installer would cover leaks caused by his faulty installation.

At least the two I have used would.

Yep - because if there is a leak - it would be noticeable in the first year, probably first few months. 3 years later...that is not something an installing company should have to cover. Waiting to notify and or doing something that caused the leak and then expecting the company to pay for it...nope

 

[eddieK]

Chinese drywall?
I

http://chinesedrywall.com/index.html

Note the rust on the sheet metal and the corrosion. That system is icing, probably from the moment it starts thru the whole cycle...most likely low charge causing refrigerant to flash in the piping.

The best way to address this is to reclaim, nitrogen test to 350 - 400 PSI and find/ seal the leak...evacuate and weigh in charge. I would not re use refrigerant and install liquid line filters on both liquid lines- I seem to recall this being a dual system.

 

[R.Anderson]

Note the rust on the sheet metal and the corrosion. That system is icing, probably from the moment it starts thru the whole cycle...most likely low charge causing refrigerant to flash in the piping.

The best way to address this is to reclaim, nitrogen test to 350 - 400 PSI and find/ seal the leak...evacuate and weigh in charge. I would not re use refrigerant and install liquid line filters on both liquid lines- I seem to recall this being a dual system.

You probably know but just in case, that is not the OP's system. That image is pulled from the Chinesedrywall.com website. Funny they compair it to a fresh install evap coil on their site.

Every mini split heat pump system I have installed had liquid and a suction line so one filter/dryer should do. Additional refrigerant maybe needed pending on the size of the filter/dryer, line set length, and requirements of the outdoor unit.

Mushcreek you should post some photos of the corrosion and your system if you can.

 

[eddieK]

You probably know but just in case, that is not the OP's system. I that is a image pull from the the Chinesedrywall.com website. Funny they compair it to a fresh install evap coil on there site.

Every mini split heat pump system I have installed had liquid and a suction line so one filter/dryer should do. Additional refrigerant maybe needed pending on the size of the filter/dryer, line set length, and requirements of the outdoor unit.

Mushcreek you should post some photos of the corrosion and your system if you can.

Dual systems have individual systems... Two liquid lines, two suction lines...He mentioned two, but he didn't say they were dual or individual, I assumed they were individual because a leak anywhere affects them both.

 

[R.Anderson]

Lol your comment makes sense now. I know how a multi zone system work, but I do not consider em two systems, one system with multiple zones. I read your comment as some sort of system I never seen or heard of where the lines get reversed between modes. So I took your comment dual system as heat or cool and you were saying put a filter on both lines to the head. I thought that as well with OP's system being a dual zone, but like wise I assume two systems as well.

Thinking about it, one filter dryer should still work with a multi zone system if it can fit. Just place it before the LEVs. I am thinking inside the box here

I did not read it any where or I missed it. Does the other system that is working have corrosion as well?

 

[MushCreek]

I haven't checked the other system, but I should. I'm recovering from a heart stent, so I'm not into climbing into awkward positions, etc.

 

[eddieK]

Lol your comment makes sense now. I know how a multi zone system work, but I do not consider em two systems, one system with multiple zones. I read your comment as some sort of system I never seen or heard of where the lines get reversed between modes. So I took your comment dual system as heat or cool and you were saying put a filter on both lines to the head. I thought that as well with OP's system being a dual zone, but like wise I assume two systems as well.

Thinking about it, one filter dryer should still work with a multi zone system if it can fit. Just place it before the LEVs. I am thinking inside the box here

I did not read it any where or I missed it. Does the other system that is working have corrosion as well?

When we buy them, they are called singular, dual or multiple.

The difference is the Condensing unit (outside)...whether it is singular (capable) dual or multiple.

Each head (indoor) has it's own liquid and suction lines. If you suspect any moisture in the system it is a good practice to install a liquid line filter drier on the liquid line. No reason to not install one on each because the charge for a single, dual or multiple operates through all of the zones, unless the valves are closed at the condensing unit.

The drier has to be sized correctly and it must be a bi flo style. One would suffice, but if there's moisture in a dual zone system, two is better, mounted just as the liquid line leaves the condensing unit.

Added : Thinking about this, the most common area where you will find a leak, especially a large one like this has, the flares. Most probably one is cracked. I see it often.