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Icing up of my heat pump - Carrier Air Conditioners

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Check your filter to make sure it isn't clogged, restricting the airflow. Also, make sure you haven't covered up any of the registers in your home, again restricting the airflow. If the airflow is good, you probably are running low on refrigerant and will need to call in someone EPA certified to check this.

Posted on Dec 16, 2008

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BUZZING NOISE FROM MY HEAT PUMP


Take a look at this YouTube page that explains with good videos what are some of the common problems with heat pump noise. The one that seems dominant is the defrost cycle a heat pump goes thru when it melts ice off the evaporative coils. In defrost cycle, The compressor runs but the cooling fan does not, so you will hear a loud buzzing sound and the unit sounds like it is stalled...because only the compressor is running to generate heat to melt coil ice.

https://www.youtube.com/results?search_query=American+Standard+5000+Heat+Pump+makes+a+buzzing+noise
Defrost cycle noise video:
https://www.youtube.com/watch?v=wudLk0WoIVo


Mar 06, 2015 | American Standard 5000 Heat Pump Unit

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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.

8a765a2.jpg
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

http://www.fixya.com/support/r3636751-air_conditioner_seer_seasonal_energy

on Jan 30, 2010 | Air Conditioners

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There is a loud humming coming from outside unit, the fan is not rotating.


Your question does not include what type of system you are asking about, but the assumption is that it is a heat pump. The loud humming is the compressor running by itself while the fan is off.

This is the typical way a reasonably new heat pump operates:
There is a coil temperature sensor that initiates a defrost period to eliminate the frost/ice build up on the outdoor coil. In the defrost mode, the outdoor fan shuts off and the reversing valve in the heat pump reverses the direction of refrigerant flow to warm the outdoor coil. The same coil temperature sensor senses the temperature of the external surface of the coil and tells the defrost control when the frost is gone initiating another 'reverse cycle' to put it back into heating mode. In the heating mode, the outdoor fan runs again.

If you have the heat pump installed where snow drifts accumulate, you will have a problem extracting heat from the outdoor air, and coil frosting and freezing will be exaggerated. If you have excessive ice build up due to a defosting issue, the ice can actually stop the fan from rotating, but you would hear loud bangind and rattling for hours first as the fan blades come in contact with the ice.

If you do not have drifts, but continually have an excessive amount of ice build up, either the sensor is possibly faulty or the defrost control board is faulty. The sensor's clip could easily have been knocked loose from the coil by ice and is no longer sensing coil temperature and if so the result would be the lack of defrost initiation.

Feb 13, 2015 | Air Conditioners

1 Answer

Unit is icing up out side while head is on


This sounds like a heat pump. Icing on the outside unit is normal for a heat pump. The defrost cycle should come on and melt the ice.

Feb 26, 2014 | Ruud Handle Air Conditioner

1 Answer

Heat pump icing up


Outside fan may not be coming on or staying on or low on refrigerant or change filter

Jan 06, 2014 | Air Conditioners

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...

2 Answers

Carrier 38CKC042300. oUTSIDE UNIT FAN WAS TURNING REAL SLOW. ac UNIT IS OFF BUT FAN TO OUTSIDE UNIT IS STILL TURNING. sHOULD NOT BE TURNING AT ALL WITH AC UNIT OFF


The outside fan may run if the unit is in defrost mode this is normal for most heat pumps it is there way of trying to keep the outside unit from staying iced over so the next time the unit runs it will have air flow through the coil and the ice will not be there to prevent air flow.

Jan 12, 2010 | Carrier 38CKC042 Air Conditioner

1 Answer

Should the LG LS-K-1830CL outdoor unit ice over on the coils when operating in the heat pump mode? Would this cause the unit to not properly heat the room?


Running the heat pump in low outside ambient temps. will definitely cause the coil to ice up. An ouside temperature senor or a wind baffle should be installed in climates that get below freezing. This would definitely cause the heat pump to operate at lowered efficency and maybe not at all. It should go into defrost mode if the sensor is working correctly when the coil ices up.

Dec 20, 2009 | LG LS-K1830CL Cool Mini Split Air...

1 Answer

Heat pump blows heat half the time and cold half the time


It sounds like it is just going into the defrost cycle. Go outside and see if it is iced up. If it is, it reverses itself to melt the ice. Heat strips should come on if unit has them

Dec 03, 2008 | Air Conditioners

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