In this video we're going to talk about a frozen air conditioning system, if you are working with a heat pump or a commercial freezer or a home refrigerator or freezer in those cases, there will be cases where freezing is normal. A heat pump and heating mode or say a freezer coil has to have a defrost cycle on it. We are talking specifically about freezing in an air conditioner, specifically diagnosing and dealing with a freezing evaporator. So, let's start with something that comes up a lot: people will see ice coming out of the cabinet or ice outside by the compressor and they'll think that's where it originates, but the ice in a system at least normally.

There are exceptions to this, of course, but normally the ice, if it exists, starts in that evaporator coil, and that is a undesired condition. You should not have ice on the coil on an air conditioner running in cooling mode, so step one. If you do find a frozen, evaporator, coil or any ice on an air conditioning system running in cooling mode first, you need to fully defrost the system. Defrost the coil and then check in the order of airflow, then look for refrigerant restrictions.

Then look for refrigerant charge! Issues and the reason i say that is because so many people rush to adjusting the refrigerant charge. You know it's the old. I think it just needs a little freon thing. That is not where you start start with.

The obvious signs of airflow then move forward from there first get the ice off if in most cases, this is just gon na mean allowing the thing to defrost. Naturally, you know shut it off with just the blower running in the case of a fan coil with the blowers over the coil. If it is a gas furnace and you have a severely frozen evaporator coil, then you're going to want to pull out the blower housing and try to manage that ice as much as possible as it melts use a shop vac. In some cases you can use a heat gun or something of that nature don't use any sort of sharp implement or any extreme heat to try to defrost a coil.

So you got to get all the ice off step number one. Do it as gently as possible step two check for a dirty air filter and don't just check in the one spot, because in some cases you get situations where people have jammed a filter into into a return or they've double filtered. So, look everywhere that a filter could be before you check anything else, next check the evaporator coil cleanliness on both sides and some systems. This can be very difficult to do if it is very difficult to do.

You can jump forward and do a static pressure drop test across the evaporator coil. If that's easier and look at the manufacturer's specifications in order to see if it's out of range for most of us, though, it's going to be just as easy to take a look at that evaporator coil and see if it is visibly dirty. Next step check your blower wheel for cleanliness and both of these cases, if they are dirty you're going to need to clean them. If you can clean them in place great, but in many cases you're going to have to pull them outside, especially with the blower wheel.

You can pull the entire assembly outside and wash it out in. The yard always remove the blower motor from the blower wheel before you attempt to clean it. Next, you want to make sure that your airflow settings are correct, so check your blower performance charts for the particular piece of equipment, you're working on make sure that your dip switches or pins or thermostat controls are set up to produce the designed airflow for the particular Piece of equipment that you have there's a lot of rules of thumb out there and some of them can be helpful for a particular market. But ultimately you need to know what the design air flow is for the system that you are working on.

What target are you trying to hit? People will throw around 350 cfm per ton or 400 cfm per tonne or 500 cfm per ton, but you need to know the design of your particular piece of equipment to know what target you are trying to hit. As an example, if you have a system, that's up in the mountains, where the air is much less dense, you have to move more air in order to do the same amount of work with the air, because the air weighs less once you've established that, then you Can do a total external static pressure test on the system to make sure that you don't have undue resistance in your ductwork, and this is only valid on a system that is already clean and once you already know, the system has been set up for proper settings Measure your total external static measure, your supply, static on the positive side and your return static on the negative side, whichever one has the higher number, is the side that you want to look at. So look for things like kinked, ductwork or ductwork, that's improperly, strapped or undersized. There are a lot of things that can go wrong with ductwork.

Even things like someone, you know pushing a couch up against the return or shutting off a bunch of registers in the house. Once you're done with that, then you want to check your refrigerant pressures and temperatures there's a whole wide range of them. This video is not about that, but you want to check your sub cooling, your super heat. You want to check your suction saturation.

You want to check your liquid saturation. A really good tip is just to use the measure quick app in order to make it easy and see. If you are in range, you want to confirm that you don't have any restrictions, so things like temperature drop across a liquid line, filter dryer. Those are the types of things you want to ensure that you do not have, and then you also want to check and make sure that your metering device is operating properly, that it's not under feeding the evaporator coil.

A lot of folks will say that a charge problem or a restriction in the liquid line won't cause freezing, really does depend on run time and the market and that you're in and how much moisture is in the air. But there are certainly cases where restrictions, whether it's an underfeeding metering device or a restricted liquid line, dryer or a system - that's just plain undercharged - can cause freeze-ups on an evaporative coil, so pay attention for that in terms of liquid line filter dryers, you want to use The same clamp on either side of the liquid line, filter dryer and make sure that you do not have a temperature drop across that liquid line, filter dryer. Anything that's measurable over one degree is an indication of a restriction in most applications. Now you want to confirm all refrigeration cycle, components and processes are functioning properly.

We say that as sort of a catch-all, because there are a lot of things that can potentially go wrong depending on the type of system you're working on and anything that causes your evaporator temperature to drop below 32 degrees. That's what causes a freezing evaporative coil! So you have to understand about suction saturation. You have to know that your system is properly matched. Obviously, if you have a evaporator coil, that's the wrong size to match the condensing unit that can cause the problem.

There's just a lot of things that could cause it, and so you have to go through and just make sure everything that's in this system is what it's supposed to be. Somebody didn't you know slam in a compressor, that's way oversized or a metering device. That's the wrong size so on and so forth, and a lot of that just requires due diligence again when you start earlier in the process and just go with the most obvious things many times, you'll find the obvious problem before you get to kind of scratching your Head here at the end and then step nine just make sure that you have the proper refrigerant charge and that's where you check your superheat sub cool, again suction saturation, liquid saturation, your condensing temperature over ambient, your design temperature differences on your evaporator coil. If you find that you're, this is completely over your head and you have no idea what i'm talking about, then you want to refer to our article on the hvacr school dot com website that talks about the five pillars of refrigeration circuit diagnosis.

But again before you get to this point start with airflow airflow is one of the largest causes of coil freezing and especially consistent coil freezing, getting the airflow settings wrong. Having a mismatched system having duct work, that's too small, dirty, blower, wheel, dirty filter. Those sorts of things are the things you want to definitely pay attention to. First, if you don't have the proper air flow over your evaporator coil, then that evaporator coil is going to run colder and is going to be prone to freeze, as always read the manual for the equipment you're working on, and you have to have some knowledge of What the proper air flow should be in order to know whether or not you hit that target, so that is it.

Those are my tips for why an evaporator, coil phrases common causes and then also what to do about it. Thanks for watching we'll catch you on the next video thanks for watching our video, if you enjoyed it and got something out of it, if you wouldn't mind hitting the thumbs up button to like the video subscribe to the channel and click, the notifications bell to be Notified when new videos come out, hvac school is far more than a youtube channel. You can find out more by going to hvacrschool.com, which is our website and hub for all of our content, including tech tips, videos, podcasts and so much more. You can also subscribe to the podcast on any podcast app of your choosing.

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