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Heat pump freezing in heat mode

My heat pump keeps freezing up in heat mode. The freezing is occurring inside the house on what I think is the coil. The copper lines that connect to unit ice over as well. I noticed a P-trap like drain system , Im not experienced with heat pumps but I know a ptrap isnt a good idea on low flow drain. Havent tested system yet after removing drain line. Any ideas as to why it would freeze its 35 degrees F out at the moment

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  • Contributor
  • 37 Answers

Your reversing valve may be faulty

Posted on Jan 18, 2013

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Posted on Jan 02, 2017

22yooper
  • 828 Answers

SOURCE: My AC unit keeps freezing

Operate your air conditioner with the fan in the on position. But first turn the fan on, turn the temp up or shut the cooling off. Your coil is more than likely frozen over. At night when outside temperature drops the refrigerant pressure and temperature in the system also drops. This action can cause icing of the cooling coil, with the fan in automatic everything shuts down at the end of a cooling cycle. Thus no air movement to melt ice on previous cooling cycle.

Posted on May 09, 2008

burzerko
  • 254 Answers

SOURCE: air conditioner freezing

Check your filter in the furnace, Then check the coil to make sure it is clean. If neither of these two solutions fix your problem you may be low on refrigerant.

Posted on Jul 23, 2008

SOURCE: the unit is not cooling. have noticed ice on the line in the unit outside.

if one or few pipe may not aproblem may be the thermostat is aet to very low cool anf the fan on low speed or the thermostat is defective also if this icing is growing up means
-1 evaporator need cleaning
- 2 a smll freon leakage

Posted on May 04, 2009

  • 286 Answers

SOURCE: The copper line going from my outside unit up to

This sounds like you are low of refrigerant. Or you evaporator needs cleaning. Have it check out to see if you have a leak in the system

Posted on Jun 16, 2009

icemelts
  • 246 Answers

SOURCE: I have a Coleman Central Air Conditioner/Heat

The most common reason for freezing up is 'air flow,' and since you've already changed your filter - have you checked out the coil (the one that cold air comes from) to see if it's clean? If the filter you changed was really 'bad dirty' then it's a good bet the coil could be dirty also - thus restricting the air flow.

If you're satisfied that the coil is clean - about the only other thing it could be - is 'low on refrigerant,' which of course will take a Service Tech to find the leak, repair it and then re-charge the unit with refrigerant.

One other thing you might think about - are you running the blower motor on 'low speed?' If you are then put it on 'high' and see what happens.

Again, the most likely cause of your problem is air flow or 'low load,' - so I would really look hard for an air flow problem of some sort.

hope this has helped a little

Posted on Jun 20, 2010

Testimonial: "I had replaced the filter on this unit with one recomended by the local hardware store and the model of my unit was on the box but the new filter was to restictive of air flow - I called the service tech who installed the unit and he immediately noted the filter that I had purchased and replaced it with a filter that he normally installs and since he put the new filter in, it works perfectly. The filter I used looked like a paper type filter and the one he used had more of a fiberglass appearance. Needless to say - his filter was the answer."

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My ac fan runs when I am in heating mode. should this happen


Yes. It is operating as a heat pump in this mode. If you notice that during the summer, when you feel the air coming off the outdoor unit, it is hot. This is the heat from the house being removed from the refrigerant that has just returned from the coil inside the house. When you switch to heating mode, you are effectively attempting to "air condition the world", so to speak. The process is reversed, with the outside coil grabbing whatever heat it can from the environment and sending it to the inside coil to be blown into the house as heat. Not as efficient as oil or gas maybe, but in moderate climes it can be cheaper overall.

Jan 26, 2016 | Heating & Cooling

Tip

A Great Tip For Saving Money


While everyone usually remembers to change their AC and Heater filters, no one thinks about cleaning the heating or cooling outdoor coil. If you have an outdoor unit for heating or cooling, those coils need to be clean too!!

The principle of an HVAC unit is to remove heat or cold from your home to make sure you have a comfortable temperature inside.

If you have a gas furnace, your good to go in the winter. Make sure you change your filter every month and you should be able to keep your home at an nice temperature for you and your family. BUT, if you have an air conditioning unit hooked up to cool your house in the spring and summer, you need to do a little maintenance every spring to make sure you get the most out of your unit and save money. The same principle works for a heat pump, so i'll break it down for each unit.

1. An air conditioning unit that has a gas heater works just like it sounds. In the winter, your thermostat will tell the heater to turn on. You will have your burner running until the fan switch in the heat exchanger gets to the right temperature to turn the fan on. This is so you don't have cold air circulating through the house. Cooling on the other hand works a little different. If your thermostat calls for cooling, your fan will turn on right away and your condensing unit outside will turn on. What you AC is doing is removing heat inside the house and putting it somewhere else. That;s where your condensing unit comes in. The heat you removed inside the house is transferred outside where it is compressed and cooled through the use of the outdoor fan.

Now, imagine if this outdoor unit has dirty coil. You are no longer able to remove the heat from the house because it's not able to be removed because of a dirty coil. This means a huge loss in cooling capacity, higher running amperage on the compressor, and your electric bill being alot larger than it needs to be. I'll have the solution after I address the heat pump.

2. Now, the heat pump. It is basically an air conditioning unit that can reverse. In the summer, the outdoor unit will blow hot because of the heat it removed in the house. In the winter, the outdoor unit will be blowing cold because it is using the heat outdoors to add heat into your house. While this sounds weird, it's engineering at it's best. In the winter, heat is able to be removed from very low temperatures and your able to transfer heat into the house because you have a compressor in your unit. It does what it says. It takes a low pressure-low temperature refrigerant and compresses it into a high pressure-high temperature refrigerant.

Now, getting to the coils of both units. You need to clean the outdoor coil on both units every spring to make sure you have a clean coil. In the long run, this will allow the unit to expell the heat gained from the house and in the long run will add life to your compressor and save you money.

On the heat pump, you'll also need to clean the coil every fall. This is because if you don't, you could have a problem with freezing your outdoor coil. If you can't remove the heat from indoors, you will slowly turn your outdoor coil into an icemaker!!

So, based on what you have, turn the power off to your outdoor unit. Spray very good with a degreaser such as simple green and let it sit for about a half an hour. Then, grab your hose and wash out the coil. You'll be amazed what comes out. Let it sit for a coup0le hours to dry out, then turn the unit on.

This will not only extend the life of your compressor, it will also save you money in the long run!!

on May 11, 2010 | Heating & Cooling

Tip

Why is Ice Forming on my Heat Pump


Many people have heat pumps and never realize that ice can form on the outdoor unit. Some have seen ice on their heat pumps but do not know how much is too much until they have a problem with not enough heat. Still others have a backup heat source and never know that they have a problem.

First off lets establish that heat pumps will form ice on the outdoor unit, usually whenever the outdoor temperatures go below about 40 degrees F. This threshold for ice depends a lot on the humidity of the air outside. If it is raining or snowing, the ice will form much more readily and rapidly. It is normal for ice to form on the outdoor unit because it is the cold side of the system when it is running in the heating mode. Because of this cooling, if the outdoor temperature is near or below freezing and there is moisture in the air, it will condense and freeze on the unit.

To keep the ice from building up to the point where it stops all the air flow, the outdoor unit will have a defrost timer board. This operates in conjunction with a sensor. Every 30 – 90 minutes the board will check the sensor. If the sensor tells the board that ice has formed on the coil it will then change the unit over from heating to cooling. This will make the outdoor unit the hot side for a short time to melt away the ice. While it does this, the unit will also energize the back up heat which is often an electric coil or a furnace. This will keep the inside air from blowing cold while the unit is defrosting.
When the sensor feels the coil temperature at about 50 degrees F it will then tell the board to return to the regular heating and switch the coils around again.

If this process fails to work for some reason the outdoor coil will become a big block of ice and look something like this.

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When your outdoor coil becomes totally frozen over it stops all the air flow through the coil and stops the heating process. In extreme case it can be very difficult and becomes a very long process to defrost the coil. You need to practice a lot of patience and care when defrosting a badly frozen coil. A torch or preferably a heat gun (hair dryer) can be used to speed up the defrost process. If it continues to occur the timer needs to be set to defrost more often or either the timer or the sensor has gone bad.

http://www.fixya.com/support/r3563896-air_conditioning__cleaning_the_condenser

http://www.fixya.com/support/r3636724-r_410a_new_refrigerant_air_conditioning

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on Jan 30, 2010 | Heating & Cooling

1 Answer

Ice on coils of heat pump not cooling


Which coil?, indoor or out? Indoor coils freeze due to clogged filters, low freon, blower motor not working. Outdoor coil freezing could mean, in rare cases in cooling mode, reversing valve not shifting.

Oct 02, 2013 | Carrier 52CQ-312-4 Comfort Series Heat...

2 Answers

I have a Mitsubishi heat pump that runs well but the outdoor unit does not defrost what could be the problem.


Why does my heat pump ice up in Winter?
Heat pumps naturally ice-up in the winter. It is normal for the entire coil to be covered in a white frost and even light ice, during cold weather conditions. However, it is bad for the entire unit to be encased in ice. This indicates ductless heat pump problems which should be addressed quickly to save energy and avoid serious damage to your ductless unit. These systems should periodically go into a defrost cycle. This keeps the unit running efficiently. If the coils are blocked by ice, proper heat transfer between the coil and the outside air will not occur.
How does the defrost mode work?
When the mini split heat pump goes into defrost, the reversing valve inside of the outdoor unit is energized, switching the system from heat to the air conditioning mode. The outdoor coil becomes the hot, the indoor coil becomes cold, and both - the outdoor and indoor fans shut off. This allows the outdoor coil to melt accumulated ice. When the built-in micro-computer analyzes that all ice have been melted, the heat pump heating system goes back to heating mode.
sanyo-mini-split-defrost.pngA cloud of water vapor may be seen rising over the outdoor unit and a "whoosh" sound can be heard as the refrigerant reverses direction. The entire process usually takes up to 10 minutes (depending on conditions).
How often does the system goes into defrost mode?
Ductless mini-split heat pumps have different ways of determining when to go into defrost. The built-in microcomputer determines outdoor temperature, refrigerant pressures, and several other factors. In colder temperatures the system will go into defrost more often than in warmer.
If a ductless mini split heat pump is severely iced-up in the winter it is possible that it isn't defrosting (though there could be many other causes). Let the manufacturer certified technician check your system

Oct 29, 2011 | Mitsubishi Mr. Slim MXZ30TN Air...

Tip

Why your unit is freezing up.


To understand why your AC or heat pump is freezing up, it helps to know how your system works.

There are 7 major parts to an AC system, 9 with a heat pump.

1 - Condenser/heat pump (The outdoor unit)
2 - Air Handler (the indoor unit unless the system is a package unit, then all is outside in one system. The air handler is usually found under the home, in an attic, or in a closet.)

In the condenser are the following major parts.

3 - Compressor
4 - Condenser coil
5 - Condenser fan
6 - (HPs only) reversing valve

In the air handler are the following major parts.

7 - Blower motor
8 - Evaporator coil
9 - (HPs only) electric heat strips

Some systems known as "dual fuel systems" use another heat source in place of the heat strips, usually a gas furnace. I will address gas furnaces in another post.

When an air conditioner is operating properly several things are taking place.

1 - The compressor is compressing or "pumping" refrigerant through the system.

2 - through changes in pressure, the refrigerant makes the evaporator coil get very cold, and the condenser coil gets very hot.

3 - The blower motor/fan circulates air across the evaporator coils, as the room temperature air (Also known as "indoor ambient") goes through the cold coil, it exits, cooled approximately 15 to 20 degrees cooler than when it entered. (In a ducted system, the blower is also the fan that circulates the air throughout the home.)

4 - The condenser fan circulates air across the condenser coils. As the outdoor air goes through the condenser coil, it removes heat from the coils that are very hot. This in turn removes heat from the refrigerant so it can run its cycle again, and through pressure changes, cool the evap coil.

5 - With a heat pump, the reversing valve reverses the flow of refrigerant in the condenser and evaporator coils.
In AC mode, the evaporator coils get cold, and the condenser coils get hot. But in heat mode, the evaporator gets very hot, and the condenser very cold.

Now, whichever coil is getting cold will freeze up if there is inadequate air flow across the coil, as the refrigerant in it is far below freezing, and there is not enough airflow to keep the humidity in the air from freezing on the coil.

Things that can cause poor airflow are,

1 - Dirty/clogged coils
2 - dirty/clogged filter (will only effect evaporator coil)
3 - Closed/blocked vents (will only effect evaporator coil)
4 - Malfunctioning or dirty fan

Low refrigerant will also cause a coil to freeze up, reduce efficiency and cause the system to run for long periods of time. Not to mention, shortening the life of the unit.

With a heat pump, in heat mode only, the condenser (outdoor) coil will routinely begin to freeze up in cold temperatures. This is due to the fact that the refrigerant is below freezing, and the cold outdoor ambient temp is not warm enough to keep the condensation in the air from freezing on the coil.

Note, a properly working AC should never freeze up.

A heat pump is equipped with defrost controls to prevent ice buildup.
Some are controlled by timers, some by temp.

When a HP is going into defrost mode, the condenser fan shuts down, the reversing valve reverses the flow of refrigerant and the once cold condenser coil now gets very hot, defrosting the coil. (Many people have said this process sounds like the unit is coming apart, or about to explode and are frightened by the "smoke" which is really just steam from melting ice that comes off the unit.)

During defrost mode, the secondary or "auxiliary" heat comes on to ensure that you are still getting warm air from the vents. (Again, this can be electric heat strips or a dual fuel system)

If you are experiencing cold air from the vents during defrost, that means your auxiliary heat is malfunctioning.

The auxiliary heat is used for three purposes.

1 - during defrost mode to maintain warm airflow (automatic)
2 - when the HP cannot maintain the set temp due to extreme outdoor temps. It comes on when the indoor temp drops several degrees below the set temp on the thermostat (automatic)
3 - For emergency heat source when the HP is not working. (Manual)

To recap....

Iced up coils?

Poor airflow
low refrigerant
Malfunctioning fan
failing defrost system


There are two things that can be done in a pinch to help de-ice frozen coils. This may get you by until the repairman can get there, or you can fix the system if you are a do-it-yourselfer.

HPs frozen outdoor coil in heat mode, not going into defrost?

Cover most of the vents, and turn the system onto cooling mode until the outdoor coil is thawed. then uncover vents and return to heat, or emergency heat. (this usually takes 15 min or less)

Frozen coils in AC mode with a heat pump?
Turn the system to heat with the thermostat on just high enough to get the system to come on. (again, usually takes 15 min or less to thaw.)

AC only, with frozen evap coils? (this can sometimes be seen frozen all the way outside to the compressor on the copper lines.)

Turn the system off, and the fan switch from "auto" to on".
This will usually defrost the coils within 1 to 2 hours.
(If your system has the furnace in line before the evap coil, turn the system to heat, and the furnace will defrost the coil within minutes.)



on Dec 25, 2008 | Carrier XHB123D X/Y Series Heat/Cool Air...

1 Answer

I have a goodman self contained heat pump that is 3 and 1/2 years old. I wake in the night to hear what sounds like the fan runnning and running and running and air moving thru the vents. Then I will hear...


Heat pumps are a very efficient design when working properly. But lose efficiency the colder it gets outdoors. I usually tell people when it drops below freezing to turn the thermostat to aux or em. heat. A heat pump can remove heat from 20°f air. But not very well. More heat at 30°f air, obviously, and so on. So the colder it is outdoors, the longer it will operate to remove heat from outdoors. And then, if it can't keep up, it brings on the electric heat elements to compensate. Now you are running both outdoor and indoor heat. This is where it's inefficient and costly. Also, the outdoor will start to freeze up. This is normal unless you can see a substantial amount of ice. The heat pump will engage defrost mode, cycling on the electric heat indoors. And defrost mode is actually cooling mode! The reversing valve in the heat pump switches to cooling mode, cycles off the outdoor fan, and defrosts for a set time or temp. So now your electric heat is engaged, and your indoor coil is a COLD coil! Not hot! Very inefficient. These 2 things are why your elec bill is higher in the winter. So it makes sense to me, if the elec heat is going to be on anyway, to move the tstat to aux or em. heat, when it's going to be below freezing outdoors. This will turn off the heat pump and use elected heat only. The only down side to this is, if you don't have enough elec heat to keep you warm, you may need both heat pump and elec heat. So trial end error until you find what works. Also, have a qualified tech check the system for operation and efficiency. Hope this helps!

Apr 08, 2017 | Goodman PHKJ048-1 Air Conditioner

1 Answer

The air conditioning fan outside the house is showing frost on the coils, what is the problem


Are you using your Air conditioner as a Heat Pump (Making heat in the house)- or as an Air Conditioner (making COLD air in the house.)

If as a heat pump, then remember-- that the WARM coil is now inside the house-- and the COLD one is outside-- So, if it is COLD outside, there is not enough HEAT out there, to keep the coil from going below freezing-- The unit may have to be turned off, and allowed to defrost, if you want more heat from the Heat Pump-

Let me know if this helped

Mack B

Jan 15, 2011 | Ruud Heating & Cooling

5 Answers

What's the difference between EM HEAT and AUX HEAT?


Sorry, neither of these answers are completely correct.
You have a heat pump (or the wrong thermostat). Let's assume you have a heat pump.

In air conditioning mode, it works like every air conditioner you have ever had, but...

In heat mode, it reverses its operation. Have you ever felt the air coming out of the outdoor unit of your A/C unit? It's hot, isn't it. And the air coming out of the indoor unit (out of the registers) is cold. Now for a heat pump to produce heat it simply runs the air conditioner in reverse and the heat comes out in the house and the cold is released outside. Neat, huh!

Here's the problem with heat pumps...when it is really cold outside the heat pump can't produce enough heat to heat your home. So it has an additional heat source called "Auxiliary Heat". This heat comes on automatically when the house doesn't get warm enough. The source of this heat is based on the region of the country you are in. North/Northeast generally have oil heat, other regions have gas, and still others have to use electricity to heat. In Texas, we usually use electricity as the supplementary heat on heat pumps. VERY EXPENSIVE!

Now the "Emergency Heat"...this is exactly as stated in Solution #2. This is manually turned on by YOU at the thermostat when your heat pump fails. This turns on the auxilliary heaters and turns off the heat pump (remember, the reverse air conditioner). Again, this can be quite expensive to run if your heat source uses electricity! Gas and oil may be cheaper. The emergency heat is only designed (normally) to keep the house livable (not comfortable) until the Heating Tech can get out to you and fix your heat pump.

Something else you should know. It is normal for a heat pump's outdoor coil to frost up during heating mode. It will detect this and go into DEFROST mode and melt the frost off the coil. While it is doing this, it will turn on the auxilliary heater to keep the air blowing in the house at a reasonable "warm" temperature, but it will not be as hot as normal. In fact, heat pumps produce a lower temperature heat than traditional heaters. So the air may feel cooler during heating than you are use to anyway. This is normal and is not a sign of a problem.

So what do you do: Set your thermostat to the temperature you want and set the controls for HEAT/COOL and FAN-AUTO/ON and leave the EMERG HEAT off unless your heat pump breaks.

As always, keep your filters clean and your outdoor unit's coils clean and free of debris.

Hope this explains your question for you!

Oct 16, 2009 | Ruud Central System Air Conditioner

1 Answer

Ac freezing outside not inside


If its in the cooling mode the ice is in both places. It freezes up inside first then works its way outside just usually not easy to see the inside ice because its incased in the coil box. This could be due to a lack of airflow ie dirty filter coil or closed dampers or low on freon. If its a heat pump and in the heating mode it could be a bad defrost control, lack of airflow across the outdoor coil or low on freon.

Sep 12, 2009 | Honeywell Electronic Programmable...

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