Heat Pumps - Trane Heat Pump CondenserHeat Pump Systems - There are different types of Heat Pumps in use in both the commercial HVAC heat pump markets and the residential HVAC heat pump markets. The two main types of heat pumps are the air source heat pumps and the water source heat pumps (or geothermal heat pumps). Within the water source heat pump types there are several sub-categories.


Heat Pumps System & Air Conditioning System Differences

For climates that require moderate heating and cooling, heat pumps offer an energy-efficient alternative option to furnaces and air conditioners. Heat pumps use electricity to move heat from a cool space to a warm space, making the cool space cooler and the warm space warmer. Air-source heat pumps require a backup method of heating for the defrost mode.

Mechanically and electrically speaking, heat pumps all work the same way but use different methods of moving the heat from one place to another. Regardless of the type of heat pump, it is, heat pumps are based on the theory of heat pumps that says heat can be moved from a warmer place to a cooler place.

Air-source heat pumps are popular in southern regions. Regions, where the temperatures in the winter are considered to be mild, are perfect for heat pumps. Water to air heat (geothermal) pumps can be used in any climate as long as there is a moderate (temperature) and reliable water source to move the heat from one place to another.

Air Source Heat Pump Tips | Dual Fuel Heating

A dual fuel heat pump is a heat pump with a gas furnace for backup heating rather than electric heat strips.

Air source heat pumps have a backup heating source. In most installations, the backup heating source is electric heat strips. Electric heat strips are very cheap to install in most cases. However, while electricity is generally regarded as 100% efficient, producing it is more costly than other heating methods. For a more efficient heat pump, consider a dual fuel heat pump, or a heat pump with a gas furnace for the backup heat source. It will be more costly to install, but your monthly bills will be reduced.

To the untrained eye, air-source heat pumps and water source heat pumps can easily be mistaken for the typical air conditioning systems. Both systems provide cooling for the structure or dwelling, but only a heat pump system can provide heating using the refrigeration process.

Both air conditioning and heat pump systems are similar in that they have similar components like a condenser coil and an evaporator coil, compressor and refrigeration lines to move the heat and refrigerant, and electrical controls in the condenser and air handler. A heat pump differs from an air conditioner with the following components:

  • A heat pump requires a heat pump thermostat to function properly for control
  • The heat pump has a reversing valve in the condensing unit to shift from heating to cooling depending on the setting of the heat pump thermostat.
  • A heat pump requires two metering devices: one for the condenser (heating mode) and one for the evaporator (cooling mode).
  • An accumulator is a necessary component for a heat pump
  • For air-source heat pumps, a backup method of heating is needed for a heat pump system.

Heat Pump Diagram

Heat Pump Refrigeration System Diagram

The Differences | Heat Pumps Heating and Cooling

Heat Pumps components differ from air conditioners in specific areas:

Unlike air conditioning systems, heat pump systems have a reversing valve in the condensing unit to reverse the flow of refrigerant and thereby the direction in which the heat is moved from one place to another. The reversing valve works off of an electrical control which requires a heat pump thermostat to energize the reversing valve.

The heat pump reversing valve switches positions depending on the thermostat setting (manually by the end-user), and this setting determines whether the heat pump unit is going to provide heating or air conditioning. Therefore, heat pumps have different control wiring than air conditioners.

Metering Device | Heat Pumps Heating and Cooling

Heat Pump Systems have an extra metering device inside of them. Typically, the type of metering device is either a fixed orifice type or a thermostatic expansion valve (TXV) type. This metering device is located near the heat pump condenser coil and meters the refrigerant into the condenser when in heating mode. When the heat pump unit is in the cooling mode, there is a bypass for the refrigerant to bypass this metering device.

Controls | Heat Pumps Heating and Cooling

A heat pump system has different HVAC electrical controls than air conditioning systems. As stated in number one, a heat pump needs a heat pump thermostat to control the system so the user can manually select between the heating and cooling modes. The heat pump thermostat controls the reversing valve on air-source heat pump systems and also controls whether the backup heat is going to energize as necessary.

The colder the temperatures drop outside, the less heat the air source heat pump can absorb. When the temperature outside drops below a certain threshold, the air source heat pump cannot keep up with providing the necessary heat to the dwelling to satisfy demand. When the temperature indoors drops below 3 degrees Fahrenheit on a heat pump system, the thermostat energizes the secondary heat, which can be either electric, gas, or oil.

The most common heat pump backup heat is electric heat because gas or oil backup heat is more expensive to install but in the long run more efficient and cost-effective than the electric heating backup.

Defrost Controls | Heat Pumps Heating and Cooling

Another area in which an air source heat pump system differs from a regular air conditioning system is that the air source heat pump needs to defrost controls. There are different methods for control the defrost cycle, but the most common is a timed method for heat pump systems. Every hour or an hour and a half, the unit automatically defrosts itself without any user input. A person standing near the outside heat pump unit will hear a loud whooshing sound and think the heat pump unit is broken.

Another sign that a heat pump system is in defrost is to observe steam rising from the heat pump condensing unit. People commonly mistake this steam for smoke and an electrical component burning. Typically, when this is observed, the heat pump unit is only defrosting itself so that it can provide the heat necessary to maintain comfortable temperatures inside the dwelling, and there is no reason for panic.

After all, if it was an electrical component and the system was installed correctly, fuses and breakers should eliminate any possibility of the heat pump having an electrical fire.

Heat Pump & Air Conditioner Advice

Regardless of the type of heat pump or air conditioner systems you have, it is important to have either type of HVAC system checked out by a professional on a regular heat pump or air conditioner maintenance schedule. This keeps the heat pump or air conditioner in tip-top shape, so it will provide reliable and efficient heating and cooling for you year-round.

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Heat Pumps