Mini Split Problem

[larrylwill]

I have had a BonAir mini split 18000 btu heat pump system since 2007. I installed it myself in my office, separate building. This past summer it started freezing up on the condenser, inside. It would cool ok for a couple hours but slowly freeze up. I put an indoor/outdoor thermostat on its output.
I would get 20 degree difference when it was working before it would freeze up. I would turn it off until the ice melted then it would be ok again for a couple hours.
I figured it was low on freon, which means a leak, I figured I would get it looked at next spring. However since it has turned cold I have been running the heat pump, even down in the single digits and it works perfect. Of course it has to defrost when its in the teens and single digits but it warms the office just fine. 25-30 degree temp difference. So now I figure maybe something wrong with the reversing valve. Tonight I turned on the air and its only blowing 12 degree difference.
Any Ideas what the problem is?

 

[Vicegrip]

put a set of gauges on it and check the charge.

 

[larrylwill]

That I can do, but mini split ductless are usually charged by weight and since I do not have a licences I cant buy the R410 anyway. I also can't find a chart to tell me if its low. A standard split system I can tell, but mini splits are a different animal.
So I am forced to hire an independent company. The company that installed my home conditioner wont touch one they didn't install, I find this more and more. They do not want any competition. However I want to know the problem before I let one take me to the cleaners. Most just want to put freon in and charge $200 knowing there is a leak and they will be back. Freon doesn't leak out unless there is a leak. If its something else I want to know the possibilities before I hire someone I don't know.

 

[Jackfre]

You are correct that the 410A ms' require a weighed charge. You are kind of over a barrel here. You can get an idea, but not a definitive one by reading high side pressure at that particular outside temp. Tech service at the manuf should have that info. You need to recover the refrigerant, do a nitrogen purge up to about 400# and find out where the leak is. It is typically the flare joints. Don't try to leak lock it. You will never get it to seal if you do. I am not familiar with your brand. How much line set do you have, what are the allowable limits for this model and what was the pre-charge on the unit.

Also, now that you are running it for heat, I'm assuming you have the condensing unit elevated off the ground. In heating the external coil will go into defrost mode and fill up the bottom of the condensing unit with condensate and then ice. The ice builds up to freeze the fan blades to the outside and then you have a whole new problem.

 

[rickairmedic]

Larry if its leaking it is most likely leaking at one of the joints where the lines go into the air handler or the heatpump itself . Look for signs of oil at these points . There are several charts available online to check your charge . You need to know the outside air temp entering the heat pump and the inside air temp entering the air handler to use most of them .


Rick

 

[larrylwill]

I installed it 3 years ago and its been in use for those three years without problems until this summer. I flared the lines and pumped them down. I don't know how much charge it had initially but It came with freon in the compressor for 20ft of lines. I used about 10ft Yes its off the ground, it has legs to hold it up. Its on concrete and on a downhill slope. Yes it does have to defrost when it gets below 17 or so but I have had it working down in the single digits. The heat pump seems to work great its only the air condition Im having problem with. Its in my test house I test integrated circuits and yesterday it got up to 60 outside and one of my testers puts out a lot of heat the room got up to 85 so I had to turn on the air and I saw the temp difference was only 12 - 15 degrees. I have seen it 20 difference last summer when it was icing up. So whatever is going on it seems to only affect the air condition and is getting worse.

 

[larrylwill]

Larry if its leaking it is most likely leaking at one of the joints where the lines go into the air handler or the heatpump itself . Look for signs of oil at these points . There are several charts available online to check your charge . You need to know the outside air temp entering the heat pump and the inside air temp entering the air handler to use most of them .


Rick

I have checked these places last summer and did not notice any oil. If it was leaking wouldn't it affect the heat side also.? I do not have any electric coils for backup. Its strictly the heat pump.

 

[larrylwill]

I called the company that installed the split whole house system before I bought the house but they wont touch any unit they didn't install and the tech got insulted when I asked him if he would work on mine on his time off since his company wouldn't touch it. So I will have to find a hens tooth, (an honest independent service tech), since even if I find the leak and thats the problem I cant buy the R410

 

[SkipsShop]

if its working fine in heat i dont think it the refrigerant,

 

[arb905]

You are probably right about the reversing valve. What type of reversing valve is it? ie does it energize for heat or for cool? Did you have to braze any lines when it was installed? Did you blow out the lines before final connection and pull the system to a 30in/hg vacuum. R-410a is very picky. It is a blend and does not like water. Any moisture in the line will gum up the components. If you pull the refigerant out of the system, you have to put new in, in a liquid form by weight. Another thing, is it freezing from the suction line to the evaporator? and does the base of the compresser freeze? Both important. Has the evaporator ever frozen up?

 

[larrylwill]

I have no idea of the type of valve. Yes 3 years ago I flushed out the lines and pulled a vacuum for about 3 hours. I wouldn't know how moister got in a 3 year old system thats been operating perfectly. It is freezing on the top of the evaporator fins only that I can see. The line out of the evaporator does not freeze.
However that was last summer, last time I used it about October or November. Last night it was just not that efficient on air condition air differential was only about 10 15 degrees. Although the heat pump 2 days ago was working great 20 degrees +, I also would not let anyone put in more freon unless he could find the leak.

 

[Eggman]

When was the last time you cleaned the coils, both the evaporator and the condensing coil. The smaller mini-splits are more sensitive to being blocked or partially blocked with debris. HTH.

Eggman

 

[larrylwill]

The inside condenser I cleaned as soon as the problem started. Its clean, I even removed the filter which was already clean. The outside I haven't looked at. Its under a building. I will check next week.
thanks

 

[arb905]

I always had problems with units that used flared fittings. You would need to get a leak detector unit that is very sensitive to small leaks. When the units run and vibrate the flare fittings will leak minute amounts. You will never find the leak when it is off and is harder when running because of the air being moved by the fans. Soap bubbles (heavy blue liquid) designed for A/C systems may produce bubbles when running if there is no airflow around the fittings. I used to have these kind of problems with small refrigeration systems. Very hard to detect a problem. 410a sytems would be even harder to seal because of the high pressures. Is there anyway to braze the lines to remove the flare fittings? In regrads to the valve, if you can used a meter to check the voltage to the reversing valve it will tell you. Some units energize the coil for cool since the heat pump cycle is the primary design of the system. It may have over time collected small amounts of moisture in the valve area and could be freezing it. Another good sign of low refrigerant or malfunctioning metering valve is the compressor will start to freeze at the suction line and work its way back to the evap coil, also make sure the evap fan is working properly, check its amp draw. Some of the small motors may start to drag and be within amp range but are moving slower than design spec, low airflow will also cause some of these problems. I hope some of this helps. It's hard to find someone to work on systems when you install them. If anything call someone and don't tell them you installed it.

 

[larrylwill]

All good ideas. All the fittings on both ends are flair, I do not know if there is a fitting that can be soldered after its screwed on or not. Since I have to find somebody to charge it if its low I will ask them if they can solder the fittings.
The only place I can find ice is on the top few coils of the inside evaporator. There is plenty of air flow. I was running it at low fan speed and set it to variable and max and it made no difference. Although I remember last summer the fan overheated 2 times and shut down. I don't know if it was froze up at the time or not. I'm surprised that this unit is not that quiet since the fan is loud. Most of what I have read says they are quieter than a window unit, if it is its not much. I also don't like the fact that in air condition mode the fan never shuts down it runs as long as its in the air condition mode. In heat it comes on and off. It is a Chinese brand that is distributed in Canada and I see the Florida company I bought from went out of business because customs wouldn't let them unload a ship full for some reason and the company had many orders and they declared bankruptcy in 2009.

 

[sneezer41]

Am I wrong in thinking that if it is icing up on the inside that it is not low on freon?

Icing could be caused by an inappropriate restriction, IE a piece of snot in the middle of the evap causing high pressure behind it and a presure drop in front of it.

Or perhaps the switch that shuts the compressor on and off is busted

 

[larrylwill]

"Icing could be caused by an inappropriate restriction, IE a piece of snot in the middle of the evap causing high pressure behind it and a presure drop in front of it."

I would think that a "piece of snot" would affect the heating cycle also or at least move it.

I don't know about the compressor switch, its to cold to run the cold cycle but I will check that when it warms u.

 

[Eggman]

Am I wrong in thinking that if it is icing up on the inside that it is not low on freon?

Icing could be caused by an inappropriate restriction, IE a piece of snot in the middle of the evap causing high pressure behind it and a presure drop in front of it.

Or perhaps the switch that shuts the compressor on and off is busted

Icing can be caused by low refrigerant charge, clogged filter, low air flow across either coil, or a combination of all issues.

 

[larrylwill]

can only be low refrigerant or mechanical because the filter and air flow is ok.