Central AC problems in winter

[Decisive]

An air conditioner is giving me a huge hassle, here's the problem and situation. Got a central AC (48K btu) disconnected from the house and ducted into the garage and setup room (18x12) cooling 8 x 1kw bare bulbs. The compressor is outside where the temperature ranges from 40 to 60 degrees farenheit. The AC has a 3600ish cfm blower recirculating a sealed room with similar cubic feet. My problem is the AC evaporator coils keep freezing over, to try and fix it we've cleaned out the blower and got the AC foam cleaning stuff and cleaned the evaporator coils. They are quite clean, after this was done airflow almost doubled out of the cold AC exhaust. With the bulbs at full and CO2 running the temp in the room was slowly dropping from 83f down to 81f but we still had the coils freezing over.

Why are these coils freezing over? And can anyone recommend a friendly, trusted AC tech in the South San Francisco Bay Area. Thanks in advance. Please let me know if i'm leaving out any info.

 

[waltwalt]

If your inside (evaporator) coils are freezing over it means your system is low on freon. I had the same problem with my mini-split system. It turned out there was a small leak in the compressor in the condensing unit. Luckily I have a friend who was "cool" and in the business.
Definitely sounds like low charge to me.
If you have a technician come over that you don't want looking at the inside unit you can make up an excuse for him not being able to access the inside unit. He can check the pressure on your lines from the outdoor unit, if theres some pressure then he might just fill it up from outside without ever needing access to the indoor unit.

If there's a leak somewhere though....

 

[PoopyTeaBags]

im guessing its snowing where you live? if so your shit is freezing you need to put a 400$ part on that literally just wraps around the condensor or some part and heats it so it dont collect ice...

i had to do that to my units in the winter so i could run a/c in my rooms.. sucks and shouldnt cost that much but thats what i was charged... Its a Kit you can buy i forget the exact name of the kit.

 

[B00420]

Yeah being low on gas will freeze you up sometimes...

Also if your room is too humid and the AC has to run ALL the time to cool then you can also get some freezing, but seems like your AC size should be enough for 8000 watts of lighting.

 

[driftersmokinjo]

I have been in the hvac business for 17 years and in that time I have seen a lot of things cause a coil to freeze. The problems presented here are causes but I would bet you could fix your problem with a 25 dollar part. What you need is a low ambient kit. What it dose is sense the suction line (the return line to the comp) temp and shut down the condenser fan to create more heat on the condenser coil. Or you could do as Poopy suggest and wrap the unit. This however I do not recommend as you cut off air flow at all times. this will cause the compressor to over heat and shorten the life. This will also cause the fan motor to draw more amps and shorten its life as well. Do some checking around at the local suply house and see if they have a low ambient kit. I can help you hook it up. Good luck!!!!!!!!

 

[driftersmokinjo]

Hmmmmmmmmm maybe I should start a 420 friendly hvac business

 

[High-Tech]

If you're AC outdoor unit is being used in the winter time, it will not work correctly and lines freeze because the hot air being expelled into cold air causes problems. Not sure exactly what it does, but the outdoor unit needs a warm area to expell the warm air. There is a unit you can attach, it runs the outdoor unit at 80% and it has some timing cycle. Not an AC guy, but when we built a room around the outdoor units, to keep them warm, they worked great after that.

 

[driftersmokinjo]

If you're AC outdoor unit is being used in the winter time, it will not work correctly and lines freeze because the hot air being expelled into cold air causes problems. Not sure exactly what it does, but the outdoor unit needs a warm area to expell the warm air. There is a unit you can attach, it runs the outdoor unit at 80% and it has some timing cycle. Not an AC guy, but when we built a room around the outdoor units, to keep them warm, they worked great after that.

How do they work in the summer with this inclosure ? And its not the hot air to the cold air that causes the unit to freeze. It is a direct relation to pressure and temperature of the freon. Im not the best teacher so i won't try to educate anyone on the fundamentals of refrigeration. I do know that if you restrict the air flow on your outdoor unit it will cause the pressure/temp of the freon to rise and will keep the indoor coil from freezing in cold temp's. I also know that if you restrict the air flow on the outdoor unit in the summer it will not cool your house properly, the compressor will be over loaded and will most likely not restart every time. This will cause compressor failure . If you have an amp prob you can do a test to check for yourself. Clamp the amp probe to ether leg of the high voltage going to the unit. See how close the amp load is to the rating on the id tag. Then close or open the air flow around the unit. If you don't have an enclosure around your unit you can use a blanket. Any air restriction will increase the amp draw.

 

[Avenger]

johnson controls part number p70aa-118c


condenser fan cycling control

 

[High-Tech]

You don't use the enclosure on the outdoor unit in the summer, only the winter. It was an immediate fix. Where the AC units were, it get's to -15C to -25C in the winter. The copper line froze solid, ice on the outside. Then when the enclosure was built, it was a 100% fix. Not sure why. Thanx Avenger, that's the part number of the 4 units that were installed later.

 

[driftersmokinjo]

Yes that control will do the trick. Sorry to sound like an ass about the enclosure. I assumed it was a permanent building. I run into things like that in the field all the time. People complain that there air isn't working and when i get there they have built something over it like a deck or just something to keep the ice out of heat pumps.

 

[Cheeb]

is it worth running a sealed room in the winter?

I've found a need to design my rooms with the ability to run sealed w/ co2/ac in the summer and vented using that cold air to my advantage in the winter.

Why not use the winter air to cool those 8k? Is it just dedication to running a sealed co2 enviroment 365 days a year?

 

[waltwalt]

It's snowing/freezing where I live and my mini-split runs no problem, the outside unit blows warm air, the lines are not sweating or freezing and the indoor unit blows cold air no problem. I would swear it actually runs better in the winter time.

This seems like an important feature people using these systems in cold climates should know about.

 

[driftersmokinjo]

The mini-split systems are the way to go if you want to heat or cool a sealed room. 1 other thing that helps the mini's is most are 410a freon which works under much more head pressure than r 22 freon. More pressure = more heat in the outdoor unit. So yes i can see a mini-split system working with out a hitch under those conditions. The only draw back is the initial cost.

 

[Decisive]

you guys are amazing thank you all for the excellent replies, as of now the problem has been solved until we get a low ambient kit by inverting the direction of the compressor fans, probably makes them run less efficient, but definitely getting that low ambient kit. Thanks again for the amazing troubleshooting and the help.