Question about Weather King 12AJA4801AH Air Conditioner

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Defrost Cycle Problems with Heat Pump

It hangs up in the defrost Cycle when it gets really cold out, causing only the Heat Strips and the Air Handler to recycle the indoor air which doesn't provide much Heat. If i bump the thermostat down causing everything to shut off, for a couple of minutes and then bump thermostat up enough to call for Heat everything comes on and works fine the rest of the day and night until it gets reall Cold out, then the same thing happens again, with the cond.unit hung up in the defrost cycle, the cond. only Humms and the fan doesn't run, what might the problem be? I suppose its in the defrost cycle and froze up. I lowered the thermostat to 65 for a couple of minutes,everything shut down, then bumped it up to 70 everything came back on, but the heat just hums and fan will not run. It tries but can't seem to get started. What can I do?

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  • lakotajack Feb 23, 2009

    Thanks very much I do appreciate your input.



    Thanks,

    Jack

  • lakotajack Feb 23, 2009

    The fan motor was shot, the reason it was just humming!!

    They replaced it, it was still under warranty.

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It's a defrost board issue. The timer on the board or something similar is hanging up. Unfortunately the solution is to replace the board. By lowering the temp. on the T-stat you are resetting the timer on the board. As you see that only works until the next cycle.

Posted on Feb 23, 2009

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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

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

HI-i have a coleman heat pump- on defrost it gives cold air- not normal. thanks


Do you have electric heat strips for auxillary or backup heat? When the heatpump goes into defrost, the electric heat strips or whatever your source of auxillary heat is, should come on to keep you from feeling the cold air. When the heat pump is in defrost it is essentially operating in the A/C mode, that is why you will feel cold air if the auxillary heat isn't working. You need find out why the auxillary heat isn't coming on if it isn't. It could be do to a bad seqencer or a burnt out element.

Mar 11, 2011 | Air Conditioners

1 Answer

Heat strips do not energize during defrost cycles air below 50 degrees up to 14 minutes


if your heat strips are not coming on, then there are a few things to check.

The first one would be that the heat strips are actually working. The easiest way to complete this task is to turn the system on into emergency heat and turn the thermostat up. If you get heat accompanied by the traditional strip heat burnt smell, then you know the electric heat strips are working.

The second thing would be that the air handler is receiving a command for heat during defrost cycle. If the command is present with no heat, then you most likely have either a wiring issue or a failed electrical relay or contactor.

The third thing would be the defrost board itself, for it is the component that calls for electric heat strips to come on during a defrost cycle. You may or may not be able to force the defrost board into a defrost cycle and then check that the heat strips are on or not.



It sounds as though your defrost board is bad with the symptoms you are describing.

Good luck.


Jan 14, 2010 | Ruud Air Conditioners

3 Answers

Goodman package- no heat below 30 degrees outside


I believe the unit you are describing is a heat pump. Heat pump are great when the temperature isn't below 30 With low ambient temps. outside it is much more efficient and comfortable to run aux. electric heat from the heat pump.

Jan 03, 2010 | Goodman PHKJ048-1 Air Conditioner

1 Answer

I have a heat pump and it freeze up


If you are referring to the outside unit freezing up, the issue is in the defrost cycle. The defrost cycle works something like this: The unit reverses the flow of freon causing the inside coil to blow cold air into the conditioned space and the outside coil is now working like an a/c unit, it gets warm to melt the frost/ice. The inside unit electric heat strips come on so you do not notice the cold air being blown in. The fan on the outside unit stops running to allow the coil to get good and warm.
Now the unit should go into the defrost cycle every 90 minutes or so. It should not terminate the cycle untill the coil is clear of frost. There is an "Klixon" type termostat that measures the temperature of the outside coil. This is most likely the problem. It is prematurely terminating the defrost cycle. I'd start there first.

Hope this helps, Let me know if I can be of any further help.

Dec 29, 2009 | Intertherm P3RC-030K Air Conditioner

2 Answers

Tempstar heat pump: want to bypass defrost thermostat


Don't attempt to bypass defrost mode. If it's cold enough to use as a heat pump, it's cold enough to need the defrost cycle.

It sounds like a sensor issue, although it may be the controller board.

Unless you know how to work on equipment like this, I urge you to get a professional to service the unit for you.

Jan 22, 2009 | Air Conditioners

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

2 Answers

Defrost Cycle Problems


You need to replace the defrost board and sensor

Nov 21, 2008 | Weather King 10AJA6001AH Air Conditioner

3 Answers

Intertherm heat pump


FIRST YOUR OUTSIDE UNIT PROVIDES HEAT BY USING A REVERSING VALVE TO CHANGE THE REFRIGERANT FLOW.THERE IS NO HEAT STRIPS OUTSIDE SECOND YOUR EMERGENCY HEAT TURNS ON ELECTRIC ELEMENTS INSIDE YOUR AIRHANDLER UNIT.IT SOUNDS LIKE SOMEONE HAS WIRED YOUR UNIT WRONG OR HAS THE THERMOSTAT SET IMPROPERLY.WHEN THE HEAT PUMP CANNOT SATTISFY THE SETPOINT THE THERMOSTAT IS SUPPOSED TO TURN ON YOUR ELEC. HEAT UNTILL THE LOAD HAS BEEN REACHED AND THE HEAT PUMP CAN CONTINUE TO MAINTAIN IT.

Nov 28, 2007 | Air Conditioners

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