Snow & Frost - Can Degrade Performance
Seeing a panel half covered in frost is normal and a sign it is working. In colder locations, when SunPump is working hard for a long time, or when there is too much R410a for an optimized balance you can see heavy frosting or icing that will reduce the heating performance if left too long. Panels completely covered in a thick layer of ice will have degraded performance, resulting in a downward spiral of less heat capacity and thicker ice. Using a Back Up is perfectly acceptable for 3-5% of all days, with less cost than over-sizing the HVAC equipment for a few weeks while being inefficient close to 50 weeks of the year. Your region will have expected weather patterns to observe, like Manitoba, Newfoundland, and North West Territories to name a few.
Our suggestion is to melt the snow and ice away using natural Solar Heat on the black aluminum panels. Avoid a reversing valve type Defrost that transfers home heat outdoors to thaw frozen equipment. SunPump 2.2 and 3.0 have a built in Defrost Circuit that works when both Ambient and Coil sensors are installed outdoors and on the panel surface. Defrost should generally be set in Parameters to Manual operation - not Automatic. SunPump 2.3 did not have Defrost, it works fine near the Coast and with auxiliary back up heating.
Cold Climate - Weather Performance
As Winter deepens there will be days when sub-zero weather will put demands on the heating system. All heat pumps have reduced heat capacity as the demand requirement increases, leaving a gap that must be filled by a booster, supplemental source, or auxiliary heating system.
Expect to switch using Parameters from Heat Pump Mode to Hybrid Mode to add the 6 kW electric hot water booster to improve recovery time.
These homes have SunPump with 6 kW electric to boost the hot water storage, and some other form of auxiliary heat source in reserve.
Near Penticton BC - December 16, 2016. High -14 C low -20 C
Near Kamloops BC - December 16, 2016. High -15 C low -22 C Note the panels are covered in snow.
It is also fine to accept that some winter days the panels are going to be covered, and as long as there is full backup, the buffer tank can be heated by an electric element during unexpected. The 1600 square foot EnerGuide 80 home is cozy with a 5.6 kW SP 2.2. Defrost is not being used, and electric element in booster mode is used.
Above is a BC mountain home on Dec 30th 2015. The current temperature at 4 pm was -6 C. Gravity is a great way to remove snow from the 12/12 pitch metal roof.
Still Heating. A close up of the 3/12 pitch shed metal roof shows the panels are completely covered with snow because Defrost is OFF
The Controller shows (rotate to right), a set temperature of 53 C and the tank at 52 C. The home is toasty-warm even with the panels covered in snow because of the backup.