Don’t Cover Your Heat Pump Or AC Unless You Read This First

Can I cover my heat pump? I get this question several times per year. My simple answer is:

Yes, you can build a cover for your heat pump, but manufacturers have strict guidelines about covering the top and sides. But there are some ways to build an outdoor heat pump cover for ice and snow that can be very easy and rewarding as a DIY project.

Heat pumps have to be treated differently than cooling-only units regarding covering because a heat pump runs all year around, and a cooling-only unit is usually not needed in winter so that it can be covered (correctly) during winter months.

Understanding the Need for Airflow in Heat Pumps and AC Units

With some instruction from me, you can get many more useful years out of that substantial outdoor unit investment.

And, by the way, I agree with those manufacturers: never cover a heat pump in a way that blocks or diverts the airflow. But I do have some heat pump cover ideas. I’ve looked at many ideas for building a heat pump cover for ice protection.

The heat pump cover ideas you see online do not all conform to manufacturers’ specifications, and many would void a warranty.

Don’t do something like this . . . . .

I installed this heat pump several years ago. The husband died, and the widow thought too much snow would get into the top of the unit, so she had her handyman build this very wrong cover over the top.

When I explained the problems it would cause, she had her handyman remove it immediately. I don’t know if she ever pulled the weeds growing around the unit’s base, obstructing airflow.

Look for that paperwork that came with your heat pump, or search it out online and find the section that has to do with clearances to the top.

Manufacturer Guidelines on Covering Outdoor Units

For example, the following is from the installation instructions for a Goodman heat pump.

Each manufacturer of HVAC equipment varies slightly on the distance from the top of the unit to the obstruction above the unit, but the message should be clear. To protect your warranty, follow the instructions.

Even the Trane WEATHERGUARD™ Top Kit that diverts the discharge air to the side doesn’t allow for obstructions above the unit within the same distance as most other heat pumps and air conditioners that discharge the air straight up.

The image above shows the top of a Trane Weatherguard unit. You can purchase just the top for your Trane unit. Just go to Amazon (#ad) to see the insanely expensive price. Be aware there is more than one size.

The image below on the left shows 5 feet from the top of the unit to any obstruction above. The image to the right refers to the runoff of rain but would probably include ice and snow falling off a roof onto the unit.

The idea behind manufacturers’ concern is that the air that flows through the unit is to be discharged far enough away from the unit to prevent it from being recycled through the unit.

Air changes temperature as air passes through an air conditioner or a heat pump. In the winter, the air through an outdoor heat pump unit is lowered by at least 10 degrees or more.

Put your hand over a heat pump while in the heat mode. The discharge air or air coming out of the fan should feel colder than the outdoor temperature.

The reverse is true when a heat pump is in the cooling mode. The air from the unit should be hotter than the ambient air.

In the heat mode, if that air is recycled through the unit, it lowers its efficiency because it uses cooler air than ambient air. And heat pumps are naturally less efficient in colder weather.

In the cooling mode, if air is recycled, it will raise the temperature of the condenser and the pressure of the compressor.

Heat transfer is a critical part of a heat pump’s operation. The ideas that some people spread are easily caught by others, like the flu. We research and then find out how wrong we can be.

Choosing the Right Cover for Heat Pumps and AC Units

Start from the bottom and go up. Make sure your outdoor unit is on a good-level pad. I like oversized pads. To keep a unit clean, an extra large pad helps keep the bark dust and grass or whatever you have just a little away from the outdoor unit.

If your outdoor unit pad has become unsightly and you’re considering a replacement, consider an oversized Diversitech (ad) precast pad. They are lightweight, durable, and not that hard to change out. And free shipping is even possible.

Go to the end of another article I wrote, where I explain how it’s possible to replace a pad under an existing unit. Care has to be taken to not create leaks in the refrigeration lines that connect the outdoor unit to the coil in your furnace. Some of those lines are short from the unit to the house.

The longer the refrigeration lines to the house, the easier it is to replace the pad. Lifting the unit to replace the pad takes some thought and effort. You may need a professional to do this.

Just measure the footprint of your unit and get one as large as you can so it fits to make a great base. Speaking of base. Did you know that all AC units and heat pumps have drain holes in the bottom of the unit?

Keeping these drain holes clear of debris is important so the unit can drain properly. Debris often piles up inside these units, and this buildup plugs these holes, causing the unit to rust and corrode. Regular maintenance (done right) should take care of the junk at the bottom, but people rarely see it unless you get right down and look closely through the fan blades.

The funny part with many units is that they don’t drain very well even when clean because the bottom pan is set flat down on the pad.

It’s much more critical for a heat pump to drain than an AC unit because its outdoor unit defrosts in the winter and drips water that can freeze in extreme weather. I wrote an entire article titled “Why’s My Heat Pump Leaking Water Outside In Winter?” all about defrost; if you care to read it, you should read it if you own a heat pump. Very educational.

If you install a new pad or are quite happy with your existing one, it’s time to raise the unit off the pad. We do this with what we call risers or pump-ups.

It is also by Diversitech and is available on Amazon. These risers need the same precautions as slipping in a new pad. Creating a leak in the refrigeration lines is an expensive repair. Again, get a professional opinion if you have concerns about doing this yourself. Click on the image to get the price and availability on Amazon.

Getting your unit up and sturdy on the pad takes at least four pump-ups. On the top and bottom of each riser are sticky pads that help secure the unit and keep it sturdy.

Surprisingly, you will notice, at least I do every time I install these, that they help quiet down the unit during operation.

With your unit up off the pad, it can drain properly, and the ice buildup at the bottom will be kept away from the unit more.

In extreme ice and snow conditions, keeping the area around the heat pump clear is always advisable, but do not pick away at ice near the bottom of the unit. Refrigeration coils are fragile and can be punctured. Very expensive.

Avoiding Common Misconceptions About Unit Coverage

Do not cover your heat pump at any time. Covers are for air conditioners or cooling-only units.

Although there is one cover that will work for both, the manufacturer offers this stipulation: “Please contact your HVAC technician before using this cover while your AC is operating.“ (#ad)

The best way can vary according to the environment. Where lots of leaves and debris can enter through the top, I like to lay a wire mesh or hardware cloth. It’s important that whatever is used does not impede the airflow.

I placed this hardware cloth over this dead heat pump for demonstration purposes. This is a half-inch mesh and has a very low restriction to airflow.

You can trim yours to fit and hold it down with plastic ties. Plastic ties will eventually become susceptible to UV rays and will give way. I don’t advise using screws unless you can see where the screw is going, and it will clear any interior parts of the unit, like the coil.

Puncturing the coil, as said before, will be an expensive repair. So with the bottom of your unit cleaned and draining correctly, you now have a preventative measure installed to stop all the crap that enters from the top.

The amount of maintenance you need to be done has been drastically reduced by stopping the addition of a screen.

A couple of types of AC covers are marketed throughout the internet. Some are complete top-to-bottom covers, such as the one below, available on Amazon.

The controversy with a complete cover has been that it allows for no airflow and will promote rust and corrosion. You are darned if you do and darned if you don’t.

Conclusion

Whatever you decide to cover your outdoor unit with should not hinder the airflow through the system. As long as you know how vital the airflow is to an AC or heat pump, you should be able to decide what kind of cover to use or if you should use a cover.

Early in this article, the essential things are building a good cover, raising the heat pump off the pad for drainage, and keeping it clean.