I am just wondering if I hooked something wrong hooking up the thermostat or perhaps I have a problem with the heat pump and need to call someone out to fix the problem. Regarding your replay to my original comment, I turned the thermostat up to 80° F. when the house temperature was 72° and the thermostat was set to heat. The supply vents did start blowing warm air. However, when I turn the thermostat back down to 73° F. the heat pump started blowing cold air again. I look forward to your answer. Thanks again for all your help!! Rebecca.
Heat Pump Blowing Cold Air | Refrigeration Heating Troubleshooting
Rebecca, thank you for your kind comments about the site!! I do work hard on it and try to answer everyone but sometimes it is difficult for various reasons. Now, to answer your question: Since you ran the little test I had you do we know your auxiliary heating or backup heat is working. That means you have a problem with the refrigeration portion of your heat pump. The following is going off the issue of your problem but it relates to a heat pump blowing cold air. Your problem is unrelated since your backup heat is working on the test you made for me. Thanks!! When your thermostat is set to heat it blows cold air when it should be blowing warm air. Of course when in heat mode, you get warm air and not cold air. That’s a no-brainer. Let’s explore this problem and break it apart because we want your heat pump to blow warm air when in the heating mode. Here are the possibilities:
- Defrost Problem
- Refrigeration Problem - yes heat pumps use the refrigeration cycle to provide heat in the winter
- Thermostat or Control Problem
- A Problem in the Condensing Unit
Let’s explore each possible heat pump problem below.
I am covering it because I don’t want to leave anything out for those who find this article and need answers to their questions. We know your backup heat works just fine so please ignore the first part of my answer. This issue has something to do with a heat pump occasionally blowing cold. This usually happens when the heat pump is not hooked up properly or the is a problem with the defrost controls.
Heat Pump Blowing Cold Air Troubleshooting Matrix
|Heat Pump Blowing Cold Air Troubleshooting Matrix|
|Defrost Cycle||1) Backup Heat is not engaging - check air handler breakers . Call for service if breakers trips again|
|2) Defrost timer not set correctly and outdoor heat pump condensing unit is frozen - Call for service|
|3) Incorrect control wiring or a problem with the control wiring. Call for service|
|Refrigeration Problems||1) Compressor not working - Call for service|
|2) Low refrigerant charge - call for service|
|3) Reversing Valvle Problem - call for service|
|Heat Pump Thermostat||1) Incorrect setting on the thermostat - double check to make sure of right settings|
|2) Wiring problem - call for service|
|3) Bad thermostat or thermostat malfunctioning - call for service|
|Heat Pump Condensing Unit||1) Breaker is tripped - check condensing unit breakers. Call for service if breakers trip again.|
|2) Mentioned above in Refrigeration Problems - reversing valve is not shifting or stuck - call for service|
|3) Mentioned above in Refrigeration Problems - Refrigeration leak - call for service|
|4) Mentioned above in Refrigeration Problems - Compressor not working - call for servce|
My Heat Pump Occasionally Blows Cold Air Problem
This happens when the heat pump shifts into defrost mode. Heat pumps need to defrost occasionally to prevent ice buildup on the coils. This is typically done by a timer built into the defrost control board. It is a defrost method used by many conventional HVAC manufacturers. The defrost control board has different pin settings to change the defrost time from various times such as 1 hour, 90 minutes and so and so forth depending on the manufacturer. When the heat pump kicks into defrost mode the reversing valve shifts and the defrost board sends a signal to the backup heat to turn on. Why do you want your backup heat on when the heat pump is in defrost mode?
Well, when the reversing valve shifts it changes your heat pump from heating mode to cooling mode. This creates heat in the coils of the condenser. The heat defrosts the coils. The problem arises when you shift the reversing valve you are also causing the evaporator coil to get really cold. This causes cold air to blow out of your vents if it is not hooked up properly.
Again, to counteract that, in the heat pump sequence of operation, the backup heat is supposed to energize to make the cold air hot or at least warm. This prevents your heat pump from blowing cold air out of the vents. I picked up a whole housing subdivision of customers because the installation contractor did not hook this up properly. I fixed it for a homeowner in that subdivision and they told their neighbors and their neighbors were calling me to fix theirs.
Heat pumps use the process of refrigeration to move heat. In the summer they move heat out of your house and the winter they move heat into your house. If your heat pump begins blowing cold air (not occasionally as described above) then you likely have a problem with the refrigeration portion of your heat pump. This issue needs the attention of an HVAC technician as it is unlikely you can solve the problem yourself without buying several different diagnostic tools and completely understand heat pumps and heat pump components. Let’s take it from the top:
Heat Pump Thermostat
First, make sure your thermostat is set to heat and you have actually increased the set point for heat. I said actually because I’ve had people decrease the set point and wondered why their heat did not work?? Anyhow, make sure you only set 1° above the house temperature. Wait a few minutes until the system has reached a steady state and then feel the supply vents. Is the temperature warm or hot? No. Then keep reading.
Now turn the thermostat up at least 5° above the house temperature. Go feel the vents again after a few minutes? Is the air coming from the vents hot or warm? No. Keep reading. Has anyone changed the thermostat recently? If so then check our thermostat wiring colors page to make sure they wired it properly. If not then keep reading. I swear you will soon find an answer to your problem for your heat pump blowing cold air.
The Condensing Unit
Problems that will cause your heat pump to blow cold air include:
- your heat pump condenser tripped the breaker so its blowing cold air. This includes electrical problems such as bad compressor contactor.
- Reversing Valve not shifting properly. Reversing valves for most heat pumps only shift for cooling. Rheem and Ruud shift the reversing valve for heating. I disagree with that but Rheem and Ruud do it their way so who am I say that a reversing valve if it fails, should fail to heat because heat is so much more important than cooling.
- Your heat pump has a refrigerant leak (Freon leak as some people call it) that needs to be repaired. Fixing a refrigerant leak is always recommended however some people simply call a contractor and the contractor oftentimes simple refills the system until you need it again. I recommend you fix the refrigerant leak.
- Something could be wrong with the compressor. It could have an electrical problem or it could have a mechanical issue. Either way a professional should troubleshoot the compressor problem and fix it. Hopefully, this is not your problem.
There are other reasons your heat pump could be blowing cold air but those are the basics. Rebecca, if I was close to where you live I would come out and take a look at your system and tell you what was wrong and repair it for you. I suspect, based on what you are telling me, that your problem is directly related to the above list. Either way, call your local contractor and have them take a look and fix it for you. Then you will definitely have hot air blowing from your vents when the cold weather hits. Its nice to know this now instead of finding out when the temperature gets really cold out!! Good luck!!
Update: Rebecca sent me an email after the contractor left her house. The heat pump is fixed. Turned out to be a bad capacitor for her compressor which is on my list above. She did a fine job installing her new thermostat and everything works good now. And the blown capacitor has nothing to do with changing her thermostat. Glad I could help!! If you have problems with your HVAC system give a shout and we will try to help you. You can use our uploader (on the menu to the right) to send us photos and a description of the problem. Rebecca used the uploader to send us some pics of her thermostat wiring and it worked great!!
Why is my Heat Pump Blowing Cold Air?