Question about Heating & Cooling

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Reversing valve Model: PHJ030-1A Seral: 9705062008 The reversing valve is not reversing to heat. I found a small hole at the condenser coil, with oil residue around the "U" shape joint. When the heat stop, the condenser froze up. I think the a/c part will continue to cool with low pressure. Could low freon keep the reversing valve from switching. Reversing valve need more pressure to work. I check coil, the ohms is 17.6, and I do have 24 volts going to the coil, but I did not check it in cool for 24 volt. What should the pressure be in temp of 50's to 30's, so I know what to do.

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  • gaclements Jan 13, 2008

    Okay, what about this. The heat pump has been down for two weeks. When I start it up it is in heat mode, the only thing that work is the A/C. There is 24 volts on the reversing valve coil. Will low pressure stop the reversing valve from switching to heat mode. The reason the condenser coil was frozen, cause the unit went in cool mode.

  • gaclements Jan 13, 2008

    O.K. This is a Goodman package heat pump. What I found is Rheem / Rudd and other are made by Goodman. Goodman the heat is the default. Other are the opposite the cool is the default. What happen was the heat went out, it automatically went to default (cool). The temp. was in upper 20's, so the condenser froze. The thermostat has not been change. This unit did not come with electric heating elements. What I 'm asking is If everything is working, will low pressure make the valve stick.

  • gaclements Jan 14, 2008

    The compressor does not make a hissing sound when in operation mode. On Goodman 24 volts is on the heat mode, not in cool mode. So, if the low pressure switch is kick out it should it show open on the meter. I think the reversing valve is stuck, cause of low pressure. What I want to know is "will low freon keep the reversing valve from switching?"

  • gaclements Jan 14, 2008

    I do not have a hissing sound coming from the compressor. The compressor is working fine. What not working is the reversing valve. So, what about the freon being low? I haven't check the pressure yet. That whty I 'm asking you about if low freon would stop the valve from switching. That's what I'm asking. What should be the pressure temp. reading in temp. in the 20's to 30's and the 30's to 40's. Without covering the package unit with a big box or tarp.

  • gaclements Jan 14, 2008

    Hey! Let say the hole was fix. What would make the reversing valve to not to work?

  • gaclements Jan 14, 2008

    O.K. This is what I'm talking about! Thanks

  • mawall Mar 22, 2008

    The unit seems to stick in cooling mode. I can shut the unit down in the early evening, start it up again and the heating mode comes on and begins taking the temperature up. However, the next morning when I return, it has gone back into cooling mode- this is when I set it to say 62 degrees and have it try to hold that temperature when no on is in the house -a B&B.

    When I put it in the thermostat control mode which varies the temperature throughout the day (in 4 time periods) it doesn't seem to do this- althouhg, I want to try this again now that I thingk about it



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The first thing you need to do is fix the hole in the coil. It will only get worse no matter what you do. The reversing valve is controlled by the thermostat, then to the defrost board, as it has a timer, sensor and all that jazz. As to your question, that is a tricky one. The way I found worked best for heat pumps is to turn it to cool. If its so cold outside that it will not turn on because of an outside thermostat, cover the coil and yourself with a cardboard box or a large tarp. Give yourself some room of course, get a set of gauges that has temp. ring for R-22.Take suction temp. from the line about 1 foot from the compressor, look at the low side of the gauge and find the temperature, not the pressure for R-22. You should have a 20 degree differential. If more than 20, add freon, less remove. This sounds a little odd, but its easy to overcharge heat pumps on the heat mode. The condenser has a sensor that switches on the electric heat if the heat pump is not working. Ice on the condenser is normal on heat mode, that's why there is a defrost board.

Posted on Jan 12, 2008

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  • Rob Luna
    Rob Luna Jan 13, 2008

    You need to determine if the reversing valve is supposed to be energized in cool or heat mode. As it is a valve it is either open or closed, so 1 makes it work and the other does nothing, being a valve, its either open or closed. I'm not doubting your statement, but the outside coil cannot freeze on cooling mode as it is filled with hot liquid turning into a gas, otherwise known as a condenser. On heat mode the outside coil is reversed to the evaporator. Every so often the defrost control will automatically switch back to cool, filling the coil with hot gas to defrost. See where I am going with this. Make sure the freon leak is fixed first, and the reversing valve is energized with power on the proper setting. There also should be a low pressure safety switch before the reversing valve. I think you may have a faulty sensor or defrost board or a stuck valve and the condenser is acting like the evaporator all the time, especially if it a Carrier brand. Just a thought, has the thermostat been changed or anything, because if the hermetic system is not functioning properly, it should kick over to the supplemental (electric heat elements) mode. You can tell by the aux or emergency heat light will be on. Miss wiring it will cause the reversing valve to operate in the opposite way its supposed to. The schematic on the unit will tell when the reversing coil should be powered. Also, does the compressor make a hissing sound when its running?

  • Rob Luna
    Rob Luna Jan 14, 2008

    Ah-ha, if you have a hissing sound coming from the compressor, the valves inside are not working correctly, and neither is the compressor. is the high pressure side a little low and the low pressure side a little high? If so, new compressor time.

  • Rob Luna
    Rob Luna Jan 14, 2008

    O.K. the reversing valve is controlled by voltage not pressure, but incorrect pressure will cause the system as a whole not to work properly, as you a seemingly experiencing. There are many variables to your answer and I gave you the super-heat method. But a number is what you want , so based on the numbers you gave me, I would say about 50lbs. on the low and 160 on high. This is affected by not only temp but fan speed, ambient temp. of inside and outside air, lenght of line set, with insulation or not, and clean coils. One of the ways to check the pressure is to feel the lines. Size of the pipe depends which mode you are in (heat or cool) so the suction or low side should be cold and have condensation on the pipe. In heat mode this will freeze kind of quickly, that's why there is a defrost cycle built in. And why I charge on cool mode if possible, because if you get frost, that means low charge. The high should be warm, or hot, depending on how much heat you are displacing. The unit does not make cold air, it removes the heat from it. Like I said previously, it is easier to charge on cool if possible because reading the lines by feel is more telling. If you want a sure way to charge, install a liquid sight glass on the high pressure side line. You will have to put it in between the compressor and reversing valve, obviously. Fix the leak, pump into a vacuum and slowly add freon until the bubbles disappear.You can also charge by weight if you are lucky enough to have the installation paperwork. The condensing unit comes pre-charged and will have an amount listed. You may have to consider a little more for the line set, between the 2 coils, based on length and diameter of the tubing, unless its less than 10 feet or so. I have asked if there is a low pressure safety. This will cause the compressor to turn off and on frequently.(short cycling) It has nothing to do with the rev. valve. It just protects the compressor from burning up from lack of lubrication. An over charge of freon will cause the system not to work properly as well as under charge. So will air in the line.



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To continue from my last Question, to do with HVAC Evaporator/Condenser Cycles, how often should the System go into Heat Standby, Heat Defrost, and Heat Modes? What are Heat Standby and Heat Defrost?

In this type of system (heat pump), the evap and condenser swap functions by means of a reversing valve, according to the mode selected. Evaps throw off cool air, condensers, warm air. In heat mode, the condenser is the indoor coil and it throws off heat from the outside air. Vice versa for the cooling mode. Heat Standby would be whenever the temperature thermistor has reached set point by the user and shuts down the system. Heat defrost is the cycle that reverses refrigerant flow and defrosts the outdoor coil by sending warm refrigerant liquid to that coil. In heat mode, the outdoor coil builds frost and ice on its surface.

Feb 05, 2015 | Refrigerators


How Heat Pumps Work

How on earth can you get hot air or hot water from very cold outside air? How does a heat pump make this heat out of cold air?
When certain gases change their state from a liquid to a gas or from a gas to a liquid the magic happens.

A heat pump can do some pretty amazing things, when it comes to making heat. To understand the way they work, you must first understand what happens when certain gases change from a liquid state to a gas and back to a liquid again. To simplify it a bit we need to look at a basic air conditioning system. The refrigerant in an air conditioning system is changing to a liquid in the outdoor condenser. The compressor compresses the gas forming a hot gas. As this gas cools under high pressure it changes into a liquid form.

Inside the indoor coil the liquid is pushed through a small hole or orifice. When it comes out the other side it rapidly changes it’s state to a gas as the pressure suddenly drops. The rapid pressure drop changes the refrigerant to a very cold gas. Air flowing over the cold gas inside the pipes makes the air cool and provides air conditioning.

Now for a heat pump the process is much the same, only coils are just switched by used a reversing valve in the outdoor condenser unit. Instead of the heat being purged to the outside from the condenser unit, the indoor unit then becomes the condenser coil. The outdoor coil becomes the cold coil and cools the outside. This is why if it is very cold outside the unit will have to run in air conditioning mode for a short time to defrost the outside cold coil. When this happens the system will usually have electric heat inside to run and keep the indoor air warm.

The reality is that a heat pump is really no more than an air conditioner running in reverse. Through the magic of using refrigerants, a heat pump can then run many times more efficiently than straight electric heat. A careful heat loss/gain should always be performed by a qualified service person before any sizing of a unit. Too large or too small of a heat pump system can make it inefficient and possibly cause it to be very uncomfortable. The longevity of the unit can also be affected by sizing and installation. Be patient and look carefully for the best contractor to install your system.

A properly designed and installed heat pump system can give you many years of comfort and efficiency. If you look for and find the contractor that can do the job right you will get many trouble free comfortable years from your heat pump unit.

on Dec 29, 2009 | Heating & Cooling


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

I'm a hvac technician myself looking for some advise

if it is a heat pump you could have a clogged actuator piston or a stuck reversing valve depending on whether the unit is energized in the heating or cooling cycle. Try pulling the wire on the reversing valve coil on and off a few times and that may force it to unstick. There is a lubricant that you can pour directly into the true suction line above the reversing valve itself. Supco oil is the name i believe. Also can try removing the actuator piston at both the condenser and the evaporator and checking to see if there is some trash in the line, especially if the lines were brazed without using nitrogen.

Jan 29, 2013 | Heating & Cooling

1 Answer

Reversing valve issues.

You will need to replace the reversing valve. You cannot replace the coil with a remote sensing bulb on this unit. Usually you know when reversing valves get stuck when you are having low side problems with heat working properly

Jun 01, 2009 | Ruud UPMC036 Air Conditioner

1 Answer

Reversing valve not switching over to air on heat pump. compressor will come on for about 10 minutes, then shut off. Hot air comes out vent.

Look for any refrigerant leaks - no or low refrigerant can cause problems in both modes. The unit may be going off on low suction.


The unit may be stuck in the heating mode.

Make sure the system is calling for the correct mode (cooling or heating) - some systems are auto, but if you can, select cooling since that is the requested mode. Check for power at the reversing valve inside the condensing unit. If power exists, then the reversing valve is stuck. It could also be the reversing valve solenoid coil, so make sure that isn't bad. There should be a strong magnetic field at the solenoid coil.

If you can hear the reversing valve clicking (moving), check the T-stat and make sure it will switch modes. Also check the reversing valve relay (those can be located in either the indoor unit or condensing unit).

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1 Answer

My intertherm heat pump has freon but will not heat is it posible that the reversing valve is stuck in the middle and will not let it heat if so where can i get a new one. My heat pump cools good and when...

You can't replace a reversing valve (must remove ALL refrigerant first), unless you are EPA certified and have the equipment to recover the refrigerant and to braze the old valve out and the new one in. That said, it's probably an electrical problem anyway. Could be the thermostat, the thermostat settings, the wiring between the thermostat and the furnace and the condenser, or the controls in the condenser - probably not in the furnace. If you don't see anything wrong you're probably gonna need a pro.

May 05, 2009 | Heating & Cooling

1 Answer

Every now and then i smell oil burning when i use my heat but u never see it on tha ground or anywhere

Most likely an oil leak around the ignition coil packs in the valve covers. Remove the center covers on the valve covers and remove the coil packs and see if you have oil in the spark plug wells and on the coil pack boots. If so you will have to replace valve cover gaskets and the orings around the coil pack holes. You can also get the coil pack boots separately if the are oil saturated.

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1 Answer

Lg minisplit heat pump will not heat

You may want to check that the pressure switch is not functioning? Secondly there is also a thermo sensor on the condenser coil which could be faulty.

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1 Answer

Fridge not getting cold

Hi you have probably a leak. must inspect all piping to see if there is some small residue of oil.if you find oil you find the leak

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