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Have problem with heat pump a/c were after 4/ to 5 hrs unit freezez its not low on freon its not fan motor its not evap coil ijust changed t stat and the funny thing about it it only freezez at 74 degree please help

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Check fans rotations for correct flow or low air flow or wrong fan speed for cool, should be hi or black and low or red for heat! ..Thank-you-very-much!

Posted on Aug 25, 2008

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I have got a gree 60000btu under ceiling unit, the suction pipe is icing up back to compressor its running on 360kPa suction and if I top up the refrigerant it does not change


major causes of evap.freezing dirty coil,evap fan motor or capacitor low on freon.moisture in system. first turn off cooling run fan to completely thaw unit. if possible clean coils and blower wheel. any unit running efficiently the evap coil will be at freezing or below. the key is to have enough airflow across the coil to remove the heat and humidity.its very easy to introduce air and moisture into the system. i have seen alot of techs. over the years make the same mistakes over and over again. when hooking up guages they dont purge the lines back; worst case is only to evacuate freon pull a vacume and recharge

May 22, 2012 | Air Conditioners

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

My air conditioner cooling coils get frozen approx\.after 2 hrs of running i have showed it to the service boy they first serviced filled gas and even changed the fan motor. but still the problem...


Hello, the evap coil will freeze from either low airflow or low charge. I would clean the coils, check air filter and replace or clean if dirty. If you have a thermometer measure the air entering the ac and the air leaving the ac, the differance should be 15-20 degrees, measure this after cleaning the coils. If it still is below 15 degrees the unit is underchraged.

May 26, 2011 | LG Heat cool Window Air Conditioner

1 Answer

The air unit is frezzing up and the air is never under 70 degress in the house! whats making it keep frezzing up?


Hi, when the unit freezes up, it is either low on freon, a plugged a/c filter, or the evaporator coil is dirty and will need to be cleaned. When the evap. coil freezes up, the blower motor can't blow air through the coil. Check the filter, and behind the filter to see if the coil is dirty, just remove the screws to excess the evap. coil on this unit. Make sure the blower motor is running up to speed also. You will know. If the coil is dirty, try and clean it the best you can and replace the filter. If it continues to ice, you will need to have the freon level checked> These are the # 1 causes of coils icing up. Please let me know how it turns out.
Sincerely,
Shastalaker7
A/C, Heating, & Refrigeration, Contractor

Aug 17, 2010 | Intertherm P3RA-048K Air Conditioner

1 Answer

The intake side, evap or condenser coil, (not sure which) ices up, not allowing airflow. best fix?


After the ice melts and you turn on the unit and your fans work the problem is your unit is low on freon normally R22 you will need to have someone who is licensed to fill it and ck for leaks. If your fan does not run replace fan first if fan runs but low air flow thru condenser or evap coil clean coil first. good luck i believe your unit is low on freon more than likely.

Aug 11, 2010 | Dometic Rooftop RV Air Conditioner

2 Answers

This is a 3 1/2 Ton unit that is low on R22 but still does cool enough to freeze up. The A/C tech insists that it needs over 4lbs of freon, does this seem right to you?


Hello TF YES to make ice on low freon you lost more than 1/2 of the factory/system charge.4 lbs is about rite.I would like to find the freon leak as you will always have to replace the gas every now & again untill found & repaired.

Aug 03, 2010 | Air Conditioners

1 Answer

Compressor keeps freezing. Then I turn it to fan and it blows tiny bits of ice out the front.


There are two major reasons an air conditioner 'freezes up.'

#1 - low on freon

This is really "not likely" - especially if the unit is fairly new and has never been 'opened up.' By 'opened up' I'm referring to a procedure where 'valves' are installed in the system: usually welded, although a less desirable way to do the same - involves a self-piercing valve that is screwed into the line.

#2 - and the 'more likely reason' for the unit to freeze up - is "lack of air across the evaporator coil." The evap coil is the one where 'cool' air comes from.

Note: you should make sure all the ice is off the unit, so, you need to run it for a good while on 'fan only' to insure all the ice is gone and you are starting with a fully defrosted unit.

a) check the filter (in front of the evap coil) and make sure it's clean. Sometimes just a dirty filter can cause the unit to freeze. Remember - the idea is to allow air to flow across the evap coil.

b) if the filter has been changed often and is 'clean' then you're probably chasing rabbits here - "but" if the filter was "dirty" it's a good bet that the coil will be dirty and you should make sure you 'clean' it real good. Once you've cleaned the filter and the coil - the unit should quit freezing up.

#2A - also involves 'air flow' and is a 'far less possibility' but still - it's possible - so I will tell you about it.
Sometimes 'motors' will start to break-down (electrically) from age or whatever. Usually the bearings (which can't be oiled anymore) will start to wear causing the fan motor to 'heat up.' When the motor 'heats up' it will cause the amps to rise and eventually the 'internal overload' which is in the motor will 'open' causing the motor to "stop." When the motor stops - air flow stops and the unit will freeze. The interesting thing and a sometimes troublesome thing from the Service Tech's veiw is - that once the motor cools off - the internal overload will 'reset' and the motor will come back on and unless someone is there to see this happen - it's always in the background of the Service Tech's thinking, i.e. is the motor cycling "on and off" on the internal overload. Like I said - this is such a rare occurance that it doesn't come into play much - but hey - it does happen - so if your coil and filter were clean - you might watch the unit and see if the motor (fan motor) is going off.

hope this helps

Jun 12, 2010 | Air Conditioners

2 Answers

For my thesis: 5 condenser problems and 5 solutions


Problem number one.

condenser fan won't come on. solution check the capacitor if good ohm out the fan to see if it is bad. If bad replace fan motor with new one.

2. compressor will not come on. solution check the contactor to see if engaging this applies to problem 1 also. If engages check the capacitor on the herm side if it is bad replace. If good check compressor to see if the compressor is bad. Should it be bad replace compressor.

3. High head pressure not cooling properly dirty condenser coils. Clean coils. With hose and water.

4. Low head pressure frosting accruing on suction line. Check freon levels. Also check inside air filter for being dirty.

5. Condenser unit is failing to come on. solution check the power source check the contactor should the main power be bad check main breaker and replace any slow blow fuses that are bad. Should the contactor be bad check transformer to ensure 24 volts going to secondary side on contactor. Inspect the two wire going to outside unit condenser. replace any broken wire any bad transformer or bad contactor.

Feb 21, 2010 | Carrier 38CKC042 Air Conditioner

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 | Air Conditioners

1 Answer

Air conditioning unit


On a "Non Heat Pump" unit, icing of the pipes is not good. It is an indication that you either have a low freon level (Charge), low load, wrong superheat.
A low load usually means, in this case, something wrong with the air flow. Clogged filter, wrong fan speed, something blocking the return air grill, like a chair/ blanket, etc.
If low on charge, the evap (Indoor Coil) will ice up and the ice will then slowly creep along the pipe untill it gets to the outdoor unit. This is really no good. Air cannot go thru solid ice so naturally there is no cooling happening.
If a company replaces the outdoor unit (Condensing Unit), there is no warranty on the indoor unit. I do not know of any company that will repair an indoor coil (Evap). Just not smart money. They have to capture the freon, open the system, make the repair, ensure the correct level of freon is in the system, and most time, add a filter/ dryer for additional filtering and drying of the freon. With all that, no one is going to patch a leak on an old coil because if it leaks now, it's going to have another soon. You'll just be chasing leaks and spend money after money. Hope that makes sense. HVAC companys have to follow the EPA rules too. Leaving a system leaking above a certain percent of it's total charge is a major no-no. They will not do it.
Hope this helps clear up a few things and good luck.

Jul 11, 2008 | Goodman CLJ30AR32 Air Conditioner

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