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Snow and ice accumulation on primarily the top of the heat pump unit is something you want to avoid. Your heat pump has a defrost cycle to fight against this, but sometimes it cannot keep up. If there is a really wet, heavy snow ice can build up on the outdoor fan. If this happens you may hear a strange noise coming from the outdoor unit and notice the outdoor cabinet is shaking or vibrating. What to do---->
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If you think there is ice out on the unit or you’re hearing it go through rather long defrost cycles, it does not hurt a thing to just put your thermostat setting to the emergency heat mode. This setting will turn off the unit outside. It turns off the heat pump and turns on your supplemental heat. It depends on your area what kind of supplemental heat you have. (Gas or electric) Feel free to use the emergency heat for a couple of days especially when conditions are really extremely snowy and cold.
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If your heat pump continues to run with a heavy build up of ice and snow, your fan and motor could malfunction. It is very hard on the heat pump to run in such an unbalanced way and that could in turn ruin the unit. It is best to turn on emergency heat and let the heat pump have a break until the build up of snow and ice can melt off the outdoor unit.