Your heat pump’s cycling frequency will vary based on several factors. This is a list that includes:
- The temperature outside
- The size of the unit
- How old the unit is
- Your home’s characteristics
That being said, your heat pump should only cycle between two and three times per hour on average. The average shutdown period should be between 10 to 20 minutes in most situations.
When the outside temperatures are too low, the heat pump has to stay on to maintain your desired temperature. This typically occurs when outdoor temperatures are 35 degrees Fahrenheit or lower.
The size of your heat pump plays a big role in how efficient it is while heating and cooling your home.
If your system is too large, it will cycle too often. And this can shorten the lifespan of the unit.
If your system is too small, then it will have to work too hard to heat or cool your home. That could also lead to the heat pump staying on longer than it normally should.
Modern heat pumps are much more efficient than older ones. If you have a newer system, then it should be able to heat your home most effectively. That should, theoretically, reduce the number of cycles that it needs to run.
But if you have an old heat pump, it might have to work harder than normal to heat your home to the same temperature. That could lead your system cycling more often than necessary.
Winter weather should only start impacting your heat pump’s cycling when temperatures drop below 35 degrees outside.
At that point, the heat pump begins losing some efficiency. And when that happens, it has to consume more energy to keep your home warm.
By the time outdoor temperatures fall to 25 to 30 degrees, the heat pump is no longer the most efficient heating option. At that point, your system may default to using a backup heating source like AUX heating to keep your home warm.
Often, when outdoor temperatures are between 30 to 35 degrees or lower, the heat pump stays on continuously. It’ll keep running if outdoor temperatures are even lower than that. But it’ll use much more electricity than it normally does.
Heat pumps in HVAC systems aren’t designed to run all the time. Their job is to bring your interior space to the temperature that you set and then turn off.
The cycling occurs when the indoor temperatures start dipping back below the temperature that you’ve set. At that point, the heat pump goes back on until the desired temperature is reclaimed. It keeps repeating this process for as long as necessary.
If your heat pump keeps turning off and on every few minutes, it’s called short cycling. This is a serious problem that you shouldn’t ignore.
For starters, constant cycling significantly increases your system’s energy consumption. It could add up to hundreds—or even thousands—of unnecessary additional energy costs each year.
The only time that it’s normal for your heat pump to run continuously is during extreme weather below 35 degrees. If your unit short cycles outside of these conditions, you’ve got a problem that needs to be fixed.
Short cycling doesn’t just increase your energy bills. It can also damage your heat pump and potentially shorten its lifespan.
That’s because short cycling puts extra strain on your system. And the extra wear and tear add up to do more damage to your unit in a shorter amount of time.
Thankfully, there are some steps that you can take to protect your heat pump from having cycling issues. Here are five ideas to prevent this problem from happening to you again in the future.
If your home holds onto heat better, then the heat pump won’t have to work as hard in extremely cold weather. That means you may not experience cycling issues during the coldest months of winter any longer.
There are lots of ways to do this. Here are some options:
- Add a moisture barrier to your home
- Use insulation with a higher R-value (R-30 for ceilings and R-11 for exterior walls at minimum)
- Seal air gaps around doors and windows
Your unit’s location can also impact its susceptibility to cycling issues.
Ideally, you should install your system on the north side of the house and enclose the outside part of your heat pump with a fence.
You also need to make sure that your installation process is done correctly. Otherwise, you could have seals that aren’t leakproof and hookups that aren’t done according to manufacturer instructions.
These little inaccuracies can add up to bring down the efficiency of your HVAC system. And over time, that can make short cycling more likely.
That’s why it’s always a good idea to have an HVAC professional install and maintain your unit instead of trying to do it yourself.
You need to be aware of a possible refrigerant leak in the future. When you have this problem, you should deal with it immediately. It affects your unit’s overall performance.
The amount of air that leaks out of your ducts can also have an impact on heat pump efficiency and short cycling.
In an ideal world, no air would leak from your ducts. But that’s just not realistic. Studies suggest that an average of 20% of energy gets wasted in ducts.
But you should aim to keep the air leakage lower than 10% of the total heat pump airflow. Doing that will require ducts that are made out of the right material and installed correctly.
Experts say that between 400 and 500 CFM of airflow should circulate through the ductwork for the optimal performance.
To achieve this, you’ll need a few things:
- Bigger ducts (if possible)
- Higher speed of fans (if possible)
- Air intake and supply registers in every room
- No blockages
It’s also really important to set your thermostat up correctly if you want to avoid short cycling.
It’s best to go with a programmable thermostat and set it up for maximum performance. The optimal indoor temperature is about 68 degrees Fahrenheit for heating and 78 degrees Fahrenheit for cooling. But you can go higher or lower than these when on vacation and based on personal preference.
Also, don’t mistakenly think that “Auto” is a more efficient setting. Using it could increase your risk of unnecessary toggling between heating and cooling, which will waste energy.
Your heat pump is most efficient when set to “Cool” mode in summer and “Heat” mode in winter.
Also, note that some programmable thermostats don’t do well with heat pumps. So you may want to consult with an HVAC specialist if you’re not sure about yours.
There are lots of different reasons why your heat pump may begin short cycling. Understanding these causes can help you brainstorm a solution for your issues.
With that in mind, here are the four most common reasons why your heat pump may be short cycling.
Your heat pump needs a steady flow of air to function properly. If it doesn’t have that, then it might start turning off and on every few minutes.
The solution is to either clean out or replace your air filters with some regularity. If you notice that your air filters are dirty, then fixing them could fix this problem for you.
It’s also possible that your thermostat is communicating inaccurate information to your heat pump. When this happens, your HVAC system may behave erratically.
A common cause of this is placing the thermostat in the wrong location. For example, you don’t want to place your thermostat near a window or a vent. Because that can impact the temperature that it reads.
It’s also possible that you’ve got faulty wiring somewhere between the heat pump and the thermostat.
When there’s hot weather outside, your unit uses its refrigerant to capture heat and push it outside.
It works the opposite way when the weather is cold. When this happens, the unit brings in warmth from outdoors, pressurizes it through refrigerant, and puts it out into your home.
When you have a refrigerant leak, none of this works correctly. The heat transfer process becomes much less efficient. It can lead to your unit not being able to complete a normal cycle.
Short cycling also occurs when your heat pump is either too large or too small. In these scenarios, it’ll either heat up your area too quickly or struggle to do so.
That’s why it’s important to make sure a professional measures out your system requirements before you buy a new one. Otherwise, you could pick incorrectly and end up having to replace your system prematurely.