Heat pumps are energy-efficient home cooling and heating systems, but the outdoor unit should be protected from snow and ice so that it can function properly during winter. Excessive amounts of frozen precipitation can cause the unit's fan to work improperly or even freeze up entirely. That's why you should consider building a simple shelter to cover your heat pump's outdoor unit during the harshest winter weather. Below is a list of tools and materials you will need followed by a step-by-step procedure for construction and installation:
What you will need
2x4 treated pine lumber
¾-inch thick treated plywood
⅜-inch diameter, 5-inch long zinc-plated lag bolts
¼-inch diameter, 3-inch long stainless steel wood screws
Aerosol can of gap-filling foam
Electric drill with ¼-inch drill bit
Ratchet and socket set
1. Measure your heat pump's outdoor unit dimensions - use a tape measure to determine the width and length of the top of the outdoor unit and record the measurements.
2. Cut the lower frame for the shelter - after determining the width and length of the unit, use a circular saw to cut two sections from 2x4 treated pine lumber that each measure the same distance as the width of the unit. Next, cut four additional sections from the same treated lumber equal to the length of the outdoor unit PLUS 3 inches. For example, if you measure the length of the outdoor unit's top to be 36 inches, then you will need to cut four pieces of lumber measuring 39 inches each.
3. Cut the vertical supports for the shelter roof - once you have cut out the six lower frame pieces, it is time to cut out the vertical supports for the shelter roof. The front two supports will be cut 2 inches less than the back two supports; this permits the roof to slope and allows snow, rain and ice to drain.
You need to make sure there is plenty of room for air to circulate above the fan, so measure and cut the two front supports from 2x4 treated lumber to a length of 36 inches. The two back supports will be cut to 38-inch lengths.
4. Cut the shelter roof surface - after the support framework is cut, lay out a rectangle on a piece of ¾-inch treated plywood that is equivalent to the measured width and length of the top of the heat pump plus 3 inches on both sides. For example, if you measured the width and length of the outdoor unit to be 38 inches by 40 inches, you will need to lay out a rectangle measuring 41 by 43 inches. After measuring and laying out the rectangle, cut it out using a circular saw and set the piece aside.
5. Assemble the shelter framework - to assemble the shelter frame, begin by bolting together two of the longest lower frame sections and the two sections you cut after measuring the width in step 2. Drill ¼-inch pilot holes through the pieces of wood and insert ⅜-inch zinc-plated lag bolts into the holes to join together the lower frame. This will form a frame that is able to just slip over the top of the outdoor unit.
To prevent the frame from sliding down the sides of the unit, you will need to install the two additional long frame sections you cut in step 2. These should be bolted on top of the frame at each of the long edges; again, use ⅜-inch lag bolts to attach these shoulder pieces. Test fit the frame to be sure the shoulder pieces now rest firmly upon top of the outdoor unit without the frame sliding or blocking the fan.
Once the lower frame is assembled, you need to add the vertical support pieces. Position each of the front vertical support pieces so they are perpendicular to the frame and are flush with the outside edges of the frame. Drill ¼-inch pilot holes and bolt the front vertical supports to the frame with the ⅜-inch lag bolts. Repeat the same process with the rear vertical supports so they are aligned with the back of the frame.
6. Place the roof on top of the assembled frame - after the framework is fully assembled, the last task is to install the plywood roof. Center the plywood roof over the four vertical supports and use ¼-inch diameter wood screws to attach the roof to the ends of the support pieces. Be careful not to drive the screws too deep or you may crush the plywood against the supports. To provide additional support and rigidity, use gap-filling foam to seal the spaces between the underside of the roof and the supports.
7. Place the assembled shelter - with help from a friend, pick up the shelter and place it on top of the outdoor unit during periods of inclement winter weather. Do not leave the shelter in place during warm weather, as the roof may interfere with the freest circulation of air and cause your heat pump to operate inefficiently.
If you have trouble performing any of these steps, consider visiting an HVAC company site like http://www.capefearair.com to contact a professional who may be able to help.