Without a doubt, the best time to maintain a heat pump is a nice warm day in the springtime. Next best would be one of those nice warm fall days. Before it gets too hot or too cold and your technicians are not too busy doing emergency calls. And, for more than one reason.

Number one, Tech’s won’t be rushed to get to the next call and they’ll take the time needed to find any obvious problems.

Number two, the refrigerant level in a heat pump is critical for efficient operation. It’s easier for HVAC service techs to get the charge “right on” when it’s in the cooling mode in that warm weather.

The correct charge can be done in heat mode and in winter as you’ll see in a video down below this. But think about the timing and the weather. Do you want your technician out freezing, hurrying through your unit to get back into his warm truck?

I’m continually educating my customers to call me during the slow season. When you don’t need heating or cooling. I know there are those parts of the country where those slow periods aren’t very long, but try for it.

Number three, in the off season when HVAC companies are generally slow, they may off some discounts on maintenance. Your should ask.

How Often Is Often Enough To Maintain A Heat Pump?

A lot of my customers ask me “how often should heat pumps be serviced?”

Once per year should offer plenty of peace of mind. On the other hand, it depends on how much maintenance you are able to do yourself and how clean the environment is in your neck of the woods.

Do you have pets that shed a lot of a bunch of new construction causing dust?

All other functions of a heat pump can be tested on that springtime maintenance call. The heat cycle with auxiliary or emergency heat, all that stuff can be checked and tested.

Personally I wouldn’t buy into those twice a year maintenance visits just because it’s a heat pump and you need to check for heating problems before winter. Don’t waste your time and money.

Things are going to break. It’s just the nature of things. All the maintenance in the world won’t stop some things from breaking.

Why Is Summer Or Warm Weather The Best Time To Maintain A Heat Pump?

I wish there was a simple answer. Here’s my attempt to be simple, because I am. A heat pump has a compressor, located outside in the unit. Compressors are just a sophisticated pump.

Compressors in HVAC systems pump against two types of valves depending on the engineers that design the unit. Because compressors pump against something they create a lot of pressure in certain parts of the system.

One of these two types of valves is an orifice which is called a piston. It’s just a tiny hole. The other type valve is called a TXV or TEV which stands for Thermostatic Expansion Valve. It’s much more complicated and actually helps make a unit more efficient than a piston does.

Heat pumps have two valves in each system. One for the compressor to pump against for the heat cycle and one for the cooling cycle. Another part called a reversing valve switches the heat pump between these valves.

If the system has too much or too little refrigerant these valves will not meter correctly and efficiency goes out the window.

There are a few methods used to find the correct charge.

  1. Charging charts
  2. Super heat
  3. Subcooling

When you understand some of these basic principles of charging it make you less vulnerable to the slip shod maintenance jobs that can come your way. Some techs may rely on your lack of knowledge to skate one by you.

Now you can ask some pertinent questions to even the best of techs and even understand what they are saying when they try to describe the condition of your unit and the processed they went through to maintain your heat pump.

So What Else Should Be Done For Maintenance Besides Getting The Correct Freon Charge?

  1. Static pressure test
  2. Auxiliary heat operation
  3. Examine all wiring and connections and electrical components
  4. Test defrost controls


I would venture to say, and this is a guess, that about 80% or more HVAC systems have never had a static pressure test. There are some amazing results and answers to problems that can be found by checking the static pressure of a duct system and even just a filter.

A test of your static pressure is a quick and painless operation. A simple meters that has a couple of probes inserted into the ducts at strategic places will give an experienced technician the results you need in about 15 minutes or less.

Did you know that each manufacture states a recommended static pressure on the label of there air handlers (furnace)?

Each furnace blower is only capable of so much air to blow. With the wrong static pressure against that blower it’s life can be in danger.

You might wonder why a system overheats or short cycles. How about lots of noise from a duct system. It might sound like a wind storm when your furnace’s blower begins it’s cycle.

Filters don’t work as well when the static pressure is too great or even not enough.

When filters don’t work correctly or are not changed at the optimum time, coils can become impacted with dust and whatever and add to the static pressure. It’s something that is not obvious in some systems. It’s a killer of compressors and utility bills.


Auxiliary heat is your systems backup heat or supplemental heat. Have you noticed on your digital thermostat the abbreviation “aux ht”? That’s telling you your electric furnace has turned on those expensive strip heaters that make your power meter spin.

I know most power meters don’t spin anymore as we’ve almost all have been converted to smart meters. I just started getting a “Weekly Energy Cost Report” in my email from my electric utility. I’d rather have the old meter back and be able to watch it spin.

Some of you may still have an old mechanical thermostat cause you’re like me and want the old stuff like power meters that spin.

If that’s you then you probably have some red and green lights that tell you when the expensive heat is spinning your meter.

Your meter could be spinning too much not only because your static pressure is off, but your Freon charge could be off also.


Examining electrical components can be tricky. Most of them you can test to see if they are operating, but the internal parts are just that, internal. Except for capacitors.

If you care to an in-depth report on how an electric furnace works go to my article describing the parts and there functions.

Capacitors are a simple part that is easy to check. They will do there part in keeping your motors running and starting correctly, but they can become weak and still operate.

An electrical meter with a micro fared reading will determine it’s efficiency. Each capacitor will have it’ value stamped on it’s side with a + or – percentage that tells the technician how far off the micro fared’s can be. If your capacitors are operating outside of that + or – percentage they should be replaced.

Capacitors are not an expense part to replace and they will assure efficient operation of your motors.

Another easy to spot electrical component is a contactor. Most contactors have open contacts that readily visible. They can appear to be burnt and should be replaced because they could have some false starts or not start at all some day soon.

Always cheaper to replace suspected parts like contactors and capacitors on an maintenance call instead of an emergency call, don’t you think?


Defrosting is really an important feature of a heat pump. Because they operate in the dead of winter those outdoor units tend to ice up. You have to realize that the cold air coming out of your duct work in the summer is now coming out the top of your heat pump in the freezing ambient of winter.

So the result is ice. That ice has to be defrosted just like your freezer full of meat. If you don’t keep the ice off then the efficiency drops and other catastrophic things can happen.

Heat pump defrost controls have timers that are adjustable to match the weather conditions of your area. Usually in increments of 30, 60, and 90 minutes. So every so often depending on your area and the settings on your defrost control, you will see that your outdoor fan quits running while the compressor is keeps running.

Your heat pump has now reversed it’s mode and it’s now in the cooling mode. Your strip heat has turned on to temper the air in your system so that you don’t feel the cold so much.

With the compressor running in the cooling mode, the outdoor coil is now the hot coil and it melting the ice off the outdoor coil. And what do you know, the ice is melting.

A defrost circuit board will have a couple of tabs that when shorted out will test the defrost cycle.

Most defrost controls have a couple of sensors connected to them. One that measures the temperature of the coil and one that measures the ambient. With these two sensors the defrost circuit board will determine when and how long to defrost.

These sensors can go out of calibration. A technician with the right tools and experience can determine if they are correct.


Manufactures of almost any kind of equipment that require any kind of maintenance will threaten, maybe that’s too strong a word, how about suggest that a program of yearly maintenance is required to enforce their warranties.

Although, I have done lots of warranty repairs over the years and cannot remember a single time when warranty was denied because maintenance was not done to any degree.

Still, the heating and air conditioning equipment in your home is a very significant investment and like a car, need to be maintained.

Make It So

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