heat pumpsDelivering energy-efficient cooling and dehumidification operation, and serving as a dual-fuel supplemental heating system, heat pumps have a lot to offer Northbrook area homeowners during summertime’s sticky heat waves and beyond. If you are contemplating a system upgrade or in need of replacement, keep reading to learn how heat pumps cool and dehumidify the home.

Heat Pump Basics

Heat pump operation for home cooling and heating works by the scientific principles of heat energy movement. Unless another force is at work (such as pressure equalization or wind) heat always seeks to equalize temperature differences by moving from a warmer place to a cooler place. Heat pumps are designed to exploit this natural heat movement by manipulating refrigerant under pressure and temperature changes to efficiently move heat out of the home (cooling mode) or into the home (heating mode). Here’s how:

  • In cooling mode, refrigerant flows into the indoor evaporator coil under low pressure.
  • The refrigerant vaporizes and becomes extremely cold.
  • Warm household airflow is pulled across the cold evaporator coil by the blower.
  • The heat energy in the airflow naturally seeks to move to the much colder refrigerant.
  • The cooled airflow is pushed through the supply ducts to the home.
  • The refrigerant is pumped to the compressor in preparation for heat release.
  • The high-pressure refrigerant vapor enters the outdoor condenser coil and is condensed into a very hot liquid.
  • The heat energy in the hot liquid refrigerant naturally seeks to move to the cooler outside air (even on very hot days, the hot refrigerant contains much more heat than outside air).
  • The cycle continues until the thermostat set point is reached.

Summertime Humidity: Sticky and Uncomfortable

The nature of indoor humidity makes it difficult to manage during the cooling and heating months, because the relative humidity changes with temperature. The amount of moisture that air can hold is based in part on the temperature of the air.

  • When air is heated, it expands and it can hold more moisture, which is why indoor air feels so dry during the heating months.
  • Conversely, when air is cooled, it contracts and therefore, holds less moisture.

Hot outside summer air can hold a lot of moisture, as you well know. When the heat pump cools warm and humid air inside the home, the cooled air contracts. This makes the air feel more humid, even though the total amount of moisture present in the air has not changed.

This is quite the conundrum. In an attempt to make household air cooler and more comfortable, the relative humidity may be increased to the point condensation forms on windows.

How Heat Pumps Cool and Dehumidify

A properly sized heat pump dehumidifies the home similarly to the way condensation forms on cooler windows when the dew point has been reached. As warm airflow is pulled across the cold evaporator coil, moisture from the warm air condenses into water on the coil. The water drips into a drain pan, and is discharged from the home through the drain tube.

The condensation and dehumidification process is naturally occurring, and needs no special considerations other than a well-maintained overall HVAC system (have you checked the air filter recently?), and specifically, a properly sized heat pump or A/C.

Matters of Heat Pump Sizing

The right balance between heat pump sizing and airflow can maximize the dehumidification process during cooling mode. If the heat pump is too large for the home and air ducts, it will frequently cycle on and off – never quite reaching peak cooling performance or peak moisture removal. You will continue to feel the effects of an overly humid home and high cooling bills.

Unfortunately, many HVAC contractors follow the old rule-of-thumb process for using a home’s square footage as the sole basis for system sizing – just to ensure there’s enough cooling power available. Many will then add some capacity just to make sure.

Conversely, if the heat pump is too small, it can’t keep up with the cooling and dehumidification demand. It will cycle on and on make a lot of noise, but under-perform for the task of cooling and dehumidifying North Shore area homes.

To maximize how heat pumps cool and dehumidify the home is a matter of correctly sizing the heat pump and ducts by accurately measuring the heat gain/loss of the home using HVAC industry best practices Manual J. If you want maximum benefit for your heat pump investment, make sure your HVAC contractor goes by the book or, better, by Manual J.

To learn more about how heat pumps cool and dehumidify the home in your North Shore community, please contact us at Roberts Heating & Air Conditioning.

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