In this 3D video, we look at the causes and effects of freezing in HVAC systems (buildup of frost or ice on the equipment).
Water freezes at 32°F or 0°F. When a surface, such as an evaporator coil, is below water’s freezing point and contains moisture, frost or ice may form on that surface. In many cases, freezing in HVAC systems starts at the evaporator coil and works its way out; freezing can happen when the suction saturation temperature stays below 32°F for an extended period of time.
Some HVAC/R applications, such as commercial freezers and heat pumps in heating mode, need to operate under below-freezing conditions; the formation of frost or ice will hinder heat transfer over time, and periodic defrosting will be required. Evaporator coils in cooling mode should NOT freeze; when freezing happens, it will block system airflow. In general, evaporator coils will be about 35°F below the return air temperature.
The rate at which freezing occurs will depend on the amount of moisture in the air, the length of time at which the evaporator coil temperature is below freezing, the temperature of the return air, the air velocity, and the overall coil design.
When you encounter a frozen system, allow it to defrost completely before troubleshooting. You may allow the system to defrost by leaving it off with (or sometimes without) the blower running. In some cases, you may be able to use a heat gun or run the heat pump in heating mode for a short period. Be mindful of the water as the ice melts and take steps to prevent water damage.
A low evaporator coil temperature may be caused by low load (low airflow and/or low indoor temperature), refrigerant undercharge, low outdoor ambient temperatures, blower issues, and refrigerant side restrictions. We can prevent low load by advising customers not to set their thermostats below 72°F in cooling mode on standard equipment. We can also prevent low airflow from being a factor by making sure we replace dirty filters and clean the evaporator coil and blower wheels as necessary. When freezing happens due to a low refrigerant charge or a restriction, we may also notice high superheat; in humid climates, freezing of this nature can cause the entire system to freeze up.
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Water freezes at 32°F or 0°F. When a surface, such as an evaporator coil, is below water’s freezing point and contains moisture, frost or ice may form on that surface. In many cases, freezing in HVAC systems starts at the evaporator coil and works its way out; freezing can happen when the suction saturation temperature stays below 32°F for an extended period of time.
Some HVAC/R applications, such as commercial freezers and heat pumps in heating mode, need to operate under below-freezing conditions; the formation of frost or ice will hinder heat transfer over time, and periodic defrosting will be required. Evaporator coils in cooling mode should NOT freeze; when freezing happens, it will block system airflow. In general, evaporator coils will be about 35°F below the return air temperature.
The rate at which freezing occurs will depend on the amount of moisture in the air, the length of time at which the evaporator coil temperature is below freezing, the temperature of the return air, the air velocity, and the overall coil design.
When you encounter a frozen system, allow it to defrost completely before troubleshooting. You may allow the system to defrost by leaving it off with (or sometimes without) the blower running. In some cases, you may be able to use a heat gun or run the heat pump in heating mode for a short period. Be mindful of the water as the ice melts and take steps to prevent water damage.
A low evaporator coil temperature may be caused by low load (low airflow and/or low indoor temperature), refrigerant undercharge, low outdoor ambient temperatures, blower issues, and refrigerant side restrictions. We can prevent low load by advising customers not to set their thermostats below 72°F in cooling mode on standard equipment. We can also prevent low airflow from being a factor by making sure we replace dirty filters and clean the evaporator coil and blower wheels as necessary. When freezing happens due to a low refrigerant charge or a restriction, we may also notice high superheat; in humid climates, freezing of this nature can cause the entire system to freeze up.
Buy your virtual tickets or learn more about the HVACR Training Symposium at https://hvacrschool.com/symposium.
Read all the tech tips, take the quizzes, and find our handy calculators at https://www.hvacrschool.com/.
Today we're going to talk about the phenomenon of frost and Ice building up on HVAC otherwise known as air conditioning systems, Why it happens and how to prevent it. Let's start with the basics. So, water freezes at 32 degrees Fahrenheit or zero degrees Celsius When a surface is below this temperature and the air around it contains moisture, Ice or Frost can form when ice forms. On an HVAC system.
it almost always starts at the evaporator and works its way out. In terms of the refrigerant side, Coil freezing occurs when the suction saturation, otherwise known as coil temperature drops below 32 degrees Fahrenheit for an extended period of time. There are certain situations in Hvacr such as the evaporator coil in a freezer or a heat pump outdoor coil running in heat mode that need to operate below freezing to transfer heat effectively. Consequently, in these cases, ice formation is normal and periodic defrosting is required.
However, an air conditioning systems in cooling mode we must keep the evaporator temperature above freezing. If not, the evaporator coil will freeze and this will block system airflow. In general, the evaporator coil will be about 35 degrees colder than the indoor temperature or the return temperature moving over the evaporator. So, if it's 75 degrees inside the house, the coil will generally be about 40 degrees or 40 degrees.
Suction Saturation: When freezing does occur, the rate at which the system freezes depends on various factors, including the amount of time, the amount of moisture in the air, the temperature of the air passing over the coil, air velocity, and coil design. Again, the ice buildup almost always starts in the evaporator coil and works its way outside. Remember, if you find a frozen system, take your time to fully defrost it before doing any troubleshooting. In this case, leaving the system off with the blower running is often a good strategy.
In some cases, you may need to leave it off entirely, and in some cases you may be able to use a heat gun or run a heat pump in heat mode for a short period of time. Always make sure to manage the water as the ice melts so as Not to cause water damage. Now let's discuss what circumstances can result in low coil temperature in the first place. Meaning, the causes of freezing: Low evaporative coil load which includes things like low airflow and low indoor temperature Not enough refrigerant in the system, low outdoor ambient temperatures, blower issues, and in some cases, refrigerant.
Side restrictions. Let's talk about low evaporator load. Low evaporator load is often due to low airflow or low indoor ambient conditions, or a combination of both. These conditions can increase the likelihood of freezing, especially during lower outdoor temperatures or when the thermostat is set lower than usual.
In general, we don't suggest that occupants set air conditioners below 72 degrees on standard equipment. Otherwise, it does increase the odds that the equipment will freeze up. Now again, it's not a matter of just set point that causes this. it's a matter of the indoor air temperature getting too low. Always look at obvious things that cause airflow problems. First and foremost, these are things like dirty air filters, dirty evaporator coils, dirty blower wheels, and other blower issues. Low refrigerant charge or restricted refrigerant flow can also result in freezing over time. This can lead to the coil simultaneously building up Frost and under feeding causing high superheat blockage and eventually a complete freeze up, especially in humid climates.
Understanding the causes of frost and ice buildup in HVAC systems is essential to maintain their efficiency and longevity. Always defrost first and look for signs of low system airflow before doing anything else to remedy the issues such as adding refrigerant.
My system freezes sometimes because the blower fails to start with the compressor. I have a split system. This can happen once or twice a month, specially during the monsoon season. I just turn off the system, wait to de-freeze and I am good for another couple of weeks until it happens again. Any ideas? Could it be the blower capacitor?
The visuals in this video 🔥🔥🔥
Just had this happen due to undersized copper tubing that wasn't replaced when the AC was updated. A nice little $1400 repair.
Does the coil temperature to air difference differ in refrigeration? I’m a refrigeration apprentice and was told the coil is 10-15° cooler than the space, but this video is saying it’s a 35° difference
Thank you. For the Information. Service area Orleans??
I like your explanation good job.
❤ Are you in Nepean ?
Good video, good reminders. Straight to the point. Got sent to deal with a frozen rooftop commercial unit last week and everyone was scratching their heads (filter is good, right? Blower's moving, right? Got pressure right?). Meanwhile nobody bothered to clean the solid compacted dust on the indoor return grills, pulling so hard it was picking them up… But hey, that's why they pay me the big bucks on colorful paper. XD
I just want to say that I really appreciate all the advice and knowledge you give to us in your videos, and I can't thank you enough for taking the time to make ones like these (with all the animations). All hats off to you and your team. 🫡
What if you have 40 degree coil, 10 degree sub cool(txv) suction 126 liquid 312 but the suction line temp doesn’t goes below 68 f? Service area Nepean??
One more small note, when it comes to airflow, always check return air vents and make sure they're not blocked or extremely dirty, because then it's exactly like having a clogged filter
I could almost smell that dirty filter- dog\human hair, degraded circa 1980's duct liner, lots of smoke particulates from Uncle Elmer's 2 pack a day Camel habit along with Auntie Ira's notorious "pine fresh" air deodorizer she incessantly sprays while maintaining a gin & tonic buzz. Are you in Ottawa ?
Thank you.😊
First art I assisted video?
Great basic fundamentals that every HVAC tech needs when diagnosing a frozen evaporator coil.
Very good Service area Ottawa??
excellent
Thankyou for the video. Please do more
Thanks a lot for this video
Great information and very clear
Good info, Thanks Bryan.
Thanks!
GREAT VIDEO THANK YOU.🥶 Are you in Kanata ?
Thank you for this!
I've asked this so many times but is this a software you are using or do you pay someone to create the video? I am an HVAC instructor and would love to make content like this for my class to cover specific lessons.
THANK s
Awesome video !!
Can you make and talk about diagnosing reversing valves ? Bypassing ?
Outstanding graphics presentation.
Thank you a lot for this channel.
Thank you!
Magnificent
Awesome video thanks for your support Are you in Barrhaven ?
great vid
The fact that you put out free education with your own time is amazing. Hope Jesus blesses you and your family mightily.😊
Great Video
🤍👍👍👍❤
Just like they taught us– back in 1972 !!!!
Great video presentation ❤
Great video and content. Thank you!