Winter is just around the corner, which means we can all look forward to months of freezing temperatures and lots of snow and ice. Cold temperatures, snow, and ice will obviously have an impact on your HVAC system and make it so that your heating system needs to run longer. Snow and ice are the biggest concerns if you heat your home with a heat pump, and this guide will show you how they can affect HVAC units.

How Snow Affects a Heat Pump

If you have a heat pump that you use to heat your home in the winter, you always need to make sure to clear away snow from the unit so that it has two to three feet of clearance on all sides. This is important for ensuring that the heat pump can work effectively. If there isn’t sufficient clearance and the sides are blocked by snow, the fan won’t be able to move air through the unit. This lack of airflow would make it almost impossible for the heat pump to work effectively and could cause it to overheat, break down, or suffer serious damage.

Even with sufficient clearance, frost and ice will start to form inside a heat pump when it runs in cold weather. The temperature of the refrigerant flowing through the coil in the heat pump is typically around 10 degrees colder than the ambient air temperature. This means a heat pump can freeze even if the outdoor temperature is above 32 degrees Fahrenheit. All heat pumps have a defrost cycle that they switch to occasionally in order to melt the ice.

The unit’s internal temperature sensor is programmed to come on at set intervals to check the temperature of the coil to see if it’s frozen. Whenever the temperature of the coil inside the unit drops below a set level, the sensor will signal the defrost cycle to start.

The reason that a heat pump needs to defrost is that all the ice that builds up on its coil will prevent the unit from working any longer. This is because the ice will insulate the coil so that air can’t reach it. If the air doesn’t come into direct contact with the coil, the refrigerant can’t capture heat, and the unit will stop working.

In order to defrost, a heat pump activates its reversing valve so that it temporarily runs in cooling mode. This means the refrigerant starts absorbing heat from the air inside the building instead of capturing heat from the outdoor air as it does when running in heating mode. This process moves hot refrigerant through the outdoor coil so that all of the ice quickly starts to melt. Most heat pumps are programmed to run the defrost cycle until the unit’s sensors detect that the temperature of the coil is around 55 degrees Fahrenheit.

It typically takes no more than 15 minutes for a heat pump to fully defrost and switch back to heating. However, you won’t have any warmth for however long it takes for the heat pump to defrost, which is why homes that have a heat pump also need a backup or auxiliary heating option.

There are times when it may take your heat pump a lot longer to defrost if the outdoor temperature is extremely cold and the coil is coated in a thick layer of ice. If your heat pump is still frozen after four hours, you’ll want to shut off the unit and call to have it inspected. A heat pump can fail to defrost for a few different reasons. The reversing valve can sometimes get stuck or fail, which will prevent it from switching to defrost mode. The temperature sensors in the unit can also fail and not signal the defrost cycle to run. In some cases, the temperature sensors can be in a location where direct sunlight hits them, causing them to think that the temperature is much warmer than it really is.

How Snow Can Affect an AC Unit

Snow and ice aren’t such issues for central AC units since they never run in the winter. However, they could be an issue if you accidentally turned your air conditioning on. This would lead to the system quickly freezing up and potentially suffering serious damage if it continued to run.

AC units are designed to be weather resistant, but it’s still not a bad idea to shovel away snow so that there’s a clear path all the way around the unit. When there’s a lot of snow drifted up around your air conditioner, it can prevent air from being able to flow through the equipment. Without adequate airflow, moisture can start to build up inside the unit and potentially lead to some of the components beginning to rust and corrode. This is especially a concern if there are lots of leaves and organic debris inside the unit since all of the debris will hold onto lots of moisture.

If you’re worried about snow affecting your AC unit over the winter, you can cover it with a piece of plywood or buy a specially made AC cover. However, it’s important that you don’t ever cover your air conditioner with plastic or any other non-breathable material. Plastic will prevent air from flowing through the unit, so moisture may get trapped inside and cause rust and corrosion to quickly form. You’re usually fine draping a tarp over the top of your AC unit as long as you only cover the top. Make sure that the sides are still fully open and that air can flow through the unit.

The Impact of Snow on a Gas Furnace

Snow and ice obviously aren’t much of an issue if your home has a furnace since the unit is located inside. The only time you ever need to be concerned about snow affecting your furnace is if it snows so much that it all piles up or drifts on your roof to where the exhaust pipe sticking up through the roof is completely covered. This is something you should always watch out for during a major snowstorm.

On most houses, you can easily see the exhaust or vent pipe from the ground. You should also be able to easily distinguish the vent pipe for your furnace from the plumbing vent stack because the furnace vent will be metal, and the plumbing vent will typically be PVC pipe. If the furnace vent pipe is buried under snow and you can’t see it, you should immediately shut off your furnace and leave it turned off until you can get the snow cleared away and the vent unburied.

If the vent pipe is buried, the exhaust fumes from the furnace will be trapped and unable to flow outside as they should. This is an extremely dangerous situation because it can allow carbon monoxide to leak out of the exhaust flue and into your home. You should always shut off your furnace until you can get the vent pipe cleared.

If you have a heat pump that isn’t working correctly or need any other heating service in Madison, you can count on Southport Home Services for help. We service, repair, and install all types of heating units, including furnaces, boilers, and heat pumps. We also offer professional air conditioning and plumbing services for both residential and commercial customers. Whether you need to have your heating system inspected or require any other HVAC or plumbing service, give us a call, and we’ll get you taken care of quickly.

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Thomas Suchla
Thomas Suchla


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