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HEAT PUMP PROBLEMS

MY HEAT PUMP SOME TIME GO TO THE MODE DEFROST EVEN IF THE SWITCH IS ON AC AND THE FAN OF THE HEAT PUMP STOP AND NO MORE COOL AIR OUT ONLY WARM. AND SOME TIME THE UNIT WORKS JUST NORMAL .I HAD A NEW DEFROST CONTROL BOARD .PLEASE SOME BODY HELPS .GOD BLESS

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  • Your an idot May 11, 2010

    did they replace the sensor and the board or just the board, what brand of equipment?

  • Dennis Boxerman May 11, 2010

    Are you saying that the defrost control board has been replaced?

  • steve
    steve May 11, 2010

    You may need to replace the defrost thermostat on the outside coil. Sounds like a bad wire sending a signal to the board to defrost.

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Defrost cycle is to allow frosy or ice to melt down and not restrict the output air. The thermostat is set too low and in high humidity ice forms quickly restricting the air flow. tur up the thermostat and let the room cool gradually.

Posted on May 27, 2009

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When the heater is on the outside ac unit runs I've temporarily turned off 220 breaker low voltage pull in switch still energized how does the furnace control board fault occur


Are you sure this is not a heat pump. The outdide unit is supposed to run with a heat pump. If its blowing cool air its likely in defrost mode, this has to happen, though you probably have heat strips inside, possibly not wired right.

Dec 18, 2016 | Heating & Cooling

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

Why contactor on heat pump will not energize heat mode?


Heat pump and AC are basically working the same principle. When you turn on the heat pump is just like to turn on the AC. The main contactor will energize to turn on the compressor. The only difference is the 3 way valve, either switching to AC mode or heat mode. It is the most commom problem for heat pump. Check the thermostat wires for heat mode and defrost control.

Feb 05, 2015 | Heating & Cooling

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

Intertherm heatpump outside fan will not come on, replace fan motor and capacitor, fan will not come on what could it be


some times heat pumps have a fan cycling switch to keep the head pressure normal in cool weather or check the defrost relay for the fan when a heat pump condenser gets frosted it will stop the fan and reverse into cooling mode for a few min. to melt the ice and this function is done by a relay or a printed circuit board if it goes bad you wont have voltage to the fan

Sep 30, 2010 | Intertherm P3RA-060K Air Conditioner

1 Answer

My heat pump is frozen up today and it is 60 degrees outside and I have my heat set to 66 degrees. Is this normal?


You post is not clear as to where the freeze-up is occurring. I'm going to assume the outdoor unit is frozen up.
Heat Pumps don't generally freeze up at 60 degrees. If the ice around the unit has an uneven pattern (for example a thick spot around the center or at the very bottom) could indicate a low refrigerant charge. If the ice is even throughout, it may be one of the following:
*Sticking Contactor*.....turn the system off at your thermostat and check to make sure the unit outside shut off. If it doesn't turn off, it is likely to be the contactor.
*Failed Defrost Thermostat*.....if the defrost thermostat fails "open", the system will never go into defrost.
*Failed Defrost Control Board*......this could also prevent the system from going into defrost
*Failed Reversing Valve*........put your system in COOL mode and check to see if it will blow cold air inside approx 16 - 22 degF lower than room temperature.
*Failed/Failing Condensor Fan Motor*.......ensure the condenser fan motor is running during heat and cool modes. The condensor fan motor will not run in OFF/Satisfied Mode or in Defrost Mode.
I hope this helps. Good Luck! :-)

Mar 05, 2010 | Heating & Cooling

1 Answer

My amana heat pump will start and run momentarily and stop several times, and eventually it works, the house stays at 70 degrees so it works but this does not sound right what's the problem if any?


Hi; I need more info. Do You mean the outdoor unit is stoping and starting while running in a call for heat by the tstat. When heat pumps run if the temperature out side reaches low enough the outside unit will go into a defrost cycle to remove any build up of frost or ice. If the outdoor unit has a dirty coil or a low freon issue this also can trick the unit into a premature defrost cycle. Now here is another scenerio.If Your ac is running in the cool mode and stops prematurly there could be several problems. Low freon level, faulty fan motor causing the compressor to go into a freon bypass mode wich sounds very spewy. Please tell me if you are in heat mode.. Also how old is the unit. Sometimes a severly worn control contactor can disallow all the needed voltage to cross over to Your fan motor and compressor. Watch unit while its acting up... Also when unit goes into a sceduled defrost the fan will stop this is normal and will restart when the unit comes out off defrost You will here this big swoosh sound. Thats the freon being redirected back into the heating path.Let me know...alpharome416

Jan 22, 2010 | Heating & Cooling

1 Answer

THANK YOU


Are you saying your air conditioner does not work? If so, make sure the ac is mode is select and not on heat. Then turn your thermostate down to around 74 degrees . The heat/cool select is on your thermostat. Good luck and keep in touch.

May 26, 2009 | Heating & Cooling

1 Answer

Compressor fan not running


Does it look like the coils are frosting over? Is it steaming? Keep watching, after about 30 min does the fan come back on?

If yes to any/all the above then the unit is probably in defrost mode and yes the fan will stop blowing during that time, but restart when the unit goes back into regular heat mode.

During this time you will likely notice warmer heat from the vents than normal and the "AUX or EM HEAT" light will be on.

That is your backup heat system. It should automatically come on during a defrost cycle.

Dec 06, 2008 | Goodman CLQ36AR49 Air Conditioner

1 Answer

High Pressure cutoff


YOUR OUTDOOR FAN MOTOR SHOULD NEVER SHUT OFF IN THE AC MODE. IT IS SUPPOSED TO SHUT OFF IN THE HEAT MODE WHEN ITS IN DEFROST. IF THE UNIT IS RUNNING IN COOL AND THE OUTSIDE MOTOR QUITS ,THE COMPRESSOR WILL QUIT SOON AFTER. EITHER THE RUN CAPACITOR FOR THE FAN IS BAD OR THE FAN MOTOR ITSELF IS BAD, IF CAP IS GOOD THEN THE MOTOR IS At FAULT. THE OUTDOOR PRESSURE SWITCH CAN ALSO OPEN IF THE INDOOR FAN MOTOR FAILS IN HEAT OR THE FILTER IS PLUM NASTY in heat OR THE INDOOR COIL IS PLUGGED UP in heat.. THE PRESSURE SWITCH USUALLY TRIPS AT 400 TO 425 SO ITS WORKING CORRECTLY. YOU MAY BE CONFUSING THE ISSUE SAYING THAT THE AIR IS HOT AND COLD INSIDE. IT IS COLD WHEN AC IS RUNNING HOT WHEN HEAT PUMP IS RUNNING IN HEAT BUT ESSENTIALLY not cold or hot if compressor isn't running, but a lot of folks describe the lack of cold air as hot when the compressor isnt running. but it basically is warm or house air temp.you test the capacitor with a capacitor tester or take it to motor shop and let them test it. odds are its a 5 , 7.5 or a 10. it should test within 10 % of rated value . ask for a RESCUE brand replacement motor. they are great ,reversable etc.carefully oil and sand the motor shaft and note exactly where the blade was located in relation to the grill so you get it back just the same. usually they wire up black to a leg of 220 power. white to the other leg of 220 power. brown and brown with white stripe to the capacitor.you can also pull whole fan shroud assembly on some units and take whole thing to motor shop and let them test motor cap, replace and all you do is return to unit and connect two power leads,

Oct 26, 2008 | Heating & Cooling

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