Question about DeLonghi Heating & Cooling

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Delonghi CP504AU Split Inverter AC system. When on heating mode, indoor fan is supposed to shut off during defrosting of external coil, but doesn't. It continues to run all the time, blowing cold air until the compressor starts again. Could this be due to a faulty temp sensor for the internal coil?

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  • rosco_carter Sep 22, 2010

    How can I check this? What component is likely to be faulty to cause the defrost interlock to not work? Does anybody know where I can get a circuit diagram for this or a similar model?

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  • Master
  • 455 Answers

Hello I think it is a faulty defrost interlock or should at least bring on 1st stage electric heat during defrost mode.

Posted on Sep 14, 2010

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Why does my sanyo model KHS2472 has a red light blinking in heat mode and a green in cooling mode, does not work in either mode makes a gurgling sound when it tries to run?


Hi,
The red light indicates it's either heating or in defrost mode
Check the outdoor unit if the compressor is running - the large pipe on the outdoor unit should be hot on heating or cool to touch on cooling
When in heating mode - the indoor fan will not start until the indoor coil is warm enough
If the reversing valve that changes from heating to cooling is faulty then you may encounter the same symptoms too
Probably need a Refrig Tech to have a look at it?
Good luck

Jan 07, 2016 | Sanyo 24KS72 Split System Air Conditioner

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

Coolant fan doesn't come on unless I run air conditioner.


"Coolant Fan" is not necessarily a common term used to refer to any particular fan in a standard HVAC system. Are you referring to the "Indoor Fan" that circulates the air within the living space???? OR are you referring to the "Outdoor Fan" or "Condensor Fan" that circulates the air across the outdoor coil ??

If its the indoor fan on an air handler that's not running unless its in A/C mode, it will be a faulty heating circuit fan relay on the main control board.

If its the outdoor fan and its a heat pump system the outdoor fan stops during the defrost mode so there is a slight possibility the system defrost board is faulty and stuck in defrost.

A little more information may help obtain a more specific answer.

Apr 14, 2015 | Heating & Cooling

2 Answers

How can ice be removed from the back of the outside component ?


The ice should shed during a normal defrost cycle. If you have extreme ice build up, you may have a problem with the defrost sensor or the defrost controller or you could be low in freeon.

Dec 24, 2014 | Sanyo 09KHS71 9,000 BTU Single Zone...

1 Answer

Coil icing up


make sure the filter is very clean. make sure all supply grills are unblocked and open. make sure the indoor fan is blowing. icing coil is normal during heating mode the system will defrost using a sensor. sometimes during cold wet weather the coil will stay iced up. sometimes in cooling mode when it is cool outside 60 degrees or less the coil will ice. low freon will make the coil ice up ,also defrost control not working will cause the coil to ice up

Sep 06, 2013 | Goodman PHKJ048-1 Air Conditioner

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...

1 Answer

DeLonghi Planus quick connect split heat pump.


I was told by a delonghi technician that it does this to defrost the unit.
Hope this helps.

Apr 16, 2009 | DeLonghi Heating & Cooling

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