No, a mini-split cannot heat and cool at the same time. Heat pump systems designed to both cool and heat can only perform one function at ago. It can either be cooling or heating – not both.
However, you’ll be glad to learn that heat pumps are highly effective. In the summer, they keep your home cool and comfortable to protect you and your family from the damaging effects of extreme heat.
They are just as effective when winter comes around. The heat pump will pump plenty of heat into your home to raise the home’s temperature to a warm, cozy level.
How Mini-Splits Cool and Heat
To understand why a mini-split cannot cool and heat simultaneously, you need first to understand how a regular mini-split system works.
Mini-splits are air conditioners that comprise separate components – an outdoor compressor unit and an indoor air handler unit – that work together to cool and heat your home, depending on the time of the year.
The compressor unit installs outdoor and comprises multiple components, chief among them a compressor and condenser. Meanwhile, indoor air handlers install indoors and are made up of an evaporator coil and a blowing system, among other components. A refrigerant line and electric wires run through the wall to connect the two parts.
The heating and cooling process is pretty straightforward, especially if you’re conversant with the working of a refrigerator.
The Cooling Process
When you need to cool the house during the summer, when you turn on the mini-split, the air handler draws indoor air into the AC system via return ducts. This air is then passed over the evaporator coils inside the air handler.
The coils carry coolant material with the capacity to absorb heat. As the hot, damp air passes over the coils, the coolant absorbs most of the heat. The amount of heat the coolant can absorb varies depending on the efficiency of the mini-split. However, most mini splits can extract up to 80% of the heat in the passing air. Some can even extract more.
After absorbing the heat, the coolant turns into low-pressure gas that’s carried outside the house to the compressor unit. Meanwhile, the now-cool air flows through a filtration system before re-entering the room via a different set of vents on the air handler known as supply vents.
The blower system inside the air handler ensures thorough and even distribution of the cool air throughout the room. The same blower is also responsible for creating an airflow cycle that allows the air handler to draw stale air via the return vents.
When the heat-laden, low-pressure gas reaches the compressor, it releases the heat, which is dumped into the air outside. Then, the gas is pressurized and sent back to the air handler inside the house to absorb more heat.
The process goes on and on until the house is cool enough in line with the thermostat setting. When the thermostat setting is reached, the cooling cycle is suspended, and the AC enters an idle or “Sleep” mode until temperatures fall below the thermostat again. At this point, the AC resumes function by initiating a new cooling cycle. Cooling cycles typically last 10 minutes and are 10 minutes apart.
The Heating Process
The first step here is to switch the AC from cooling mode to heating mode. Remember that this is only possible for heat pumps. If the mini-split is purely an air conditioner, it won’t have a heating mode.
After switching to heating mode, when you turn on the heat pump, the compressor unit extracts heat from the air outside the house and transports it via the refrigerant to the air handler. As cold air passes through the air handler, the heat in the refrigerant is transferred to it, thus raising the temperature.
The now-warm air is then pushed out of the air handler by the blower system. The blower also ensures even distribution of the warm air throughout the room.
Here too, the amount of heat transferred varies from one mini spit to the next. However, the process goes on and on until the thermostat setting is reached. At this point, the heating cycle is suspended until ambient temperatures inside the room fall below the thermostat setting.
It’s Either Heating or Cooling
From the working mechanism, you can tell that heat pumps can provide both cooling and heating. However, they can’t do both simultaneously. It’s either cooling or heating – but not doing both simultaneously.
What if you need Simultaneous Cooling and Heating?
A few applications may require simultaneous heating and cooling. This is particularly common in commercial settings. A few examples include;
Data centers produce massive amounts of heat. Even during the cold season, when the rest of the office is freezing, the data center will be boiling hot. In this case, you may want an HVAC appliance that can heat and cool simultaneously so that you can cool the data center while heating the rest of the office.
Commercial kitchens are another area that’s always hot no matter the time of the year. Even in the heart of winter, when the rest of the restaurant is freezing, people in the kitchen will be in a different world where heat is the main concern. Here too, a system that can heat and cool simultaneously would be desirable.
Some building layouts
In layouts where some rooms are located at the center of the building, several rooms away from the exterior wall, the rooms might have different temperatures. Typically, rooms located away from the exterior walls are warmer, even during the cold season when exterior walls are very cold. This is another scenario when an HVAC system with simultaneous cooling and heating capacity would be valuable.
Solutions to Consider
Fortunately, there are unique HVAC systems explicitly designed with such situations in mind. We recommend the following two options;
Four-pipe HVAC systems
Standard air handlers in hydronic HVAC systems typically have a supply pipe and a return pipe. This way, the system can circulate hot water from a boiler or cold water from a chiller – but not both.
However, 4-pipe systems are different. They have a similar layout but with two supply pipes and two return pipes. This way, you can send cold water from the chiller to one air handler and hot water from the boiler to the next air handler. The chiller and boiler are also designed to operate simultaneously.
Variable Refrigerant Flow Systems
Variable refrigerant flow (VRF) systems are a new breed of highly efficient HVAC systems. They come with outdoor units with both heating and cooling functions, connected via indoor fan coils through refrigerant lines. The units can deliver simultaneous heating and cooling in two ways.
First, you can have one supply and one return line for each coil, with a central branch selector that allows you to choose superheated or super-cooled refrigerant, depending on your needs.
Alternatively, you can opt for a configuration with three lines for each fan coil. One line for cooling, the other for heating, and the third is a common return line in such configurations.
Standard mini split air conditioners cannot heat and cool and heat simultaneously. Although mini-split heat pumps are designed to perform both functions, they can only heat or room, but not do both at a go.
However, if you seriously need simultaneous heating and cooling, solutions exist, such as four-pipe HVAC systems and variable Refrigerant Flow (VRF) systems.