Welcome to the NEST Resources Page (UNDER CONSTRUCTION)
This page is designed to provide more in-depth information for those wishing to dig deeper into the technology and policies of our various programs. This will serve as a curated (and often updated) source of news and educational content to help you enhance your understanding of these topics.
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How does a heat pump operate?
Heat pumps transfer air from one space into another instead of burning fossil fuels to produce heat.
They work to transfer hot air from the air or ground into your home in the winter and work in reverse in the summer months. As shown in the diagram, there are four main parts to a system; the evaporator, condenser, compressor, and expansion device.
Heat pumps can look different depending on the type of system and units you have installed. The three kinds of systems that NEST assists with are ground source (geothermal), air source, and heat pump water heaters, covered below.
Check this video out to learn more!
Geothermal (Ground Source)
Ground source heat pumps take advantage of the naturally occurring difference between the above-ground air temperature and the subsurface soil temperature to both heat and cool buildings. This works because the ground temperature is warmer than the air in the winter and cooler than the air in the summer.
As for efficiency, ground source heat pumps require a small amount of electricity to drive the heating and cooling process. For every unit of electricity used, the heat pumps can deliver as much as five times the energy from the ground.
Types of Geothermal Loops
A ground source system consists of a heat pump connected to a continuous loop of piping that exchanges energy with the ground. There are two types of geothermal loops.
The loop is buried either horizontally in trenches just below the ground or vertically in holes that go several hundred feet below the ground. The heat pump then circulates a fluid, sometimes water, through the pipes to move heat from point to point.
Three Points of Connection
There are 3 points of connection in a ground source loop, the earth, the pump, and the distribution system.
At the ground level, there are a series of connected pipes buried near the building. The fluid that circulates in the loop absorbs or relinquishes heat to the surrounding ground.
The heat pump works both to heat and cool. To heat, the pump removes the heat from the circulating liquid, concentrates it, and then transfers it to the building. To cool, the pump removes heat from the air in the building, concentrates it, and then transfers it back to the circulating liquid.
Distribution systems can be of various forms including: forced air through conventional ductwork (pipes, vents), hydronic (water), radiators, and radiant.
Air Source
Air source systems use electricity to power a compressor and two coils (one indoors and one outside), which aid in heat transfer.
In heating mode, liquid in the outside coil removes heat from the air and evaporates it into gas, then the indoor coil releases the heat to the inside of your house as it condenses the gas back into liquid.
When operating in reverse, the direction of the liquid flow is changed to facilitate cooling, by removing heat from the interior and releasing it outside.
Types of Air Source Systems
There are numerous types of air source systems. Below, we will cover the difference between duct-less and ducted, split and packaged, and single and multi-zone systems.
Ducted versus Duct-less
Ductless systems require minimal construction. Only a 3-inch hole through the wall is required to connect the system.
Ducted systems simply use ductwork and can use new or existing ventilation systems.
Short-run have traditional, large ductwork that runs through a small section of the house. It is often complimented with ductless units for the remainder of the house.
Split versus Packaged
Split systems have coils on the inside and outside, and supply and return ducts connect to the indoor central fan.
Packaged systems have coils and fans outside, and heated or cooled air is delivered indoors from ductwork.
Single-Zone versus Multi-Zone
Single-zone (top) systems are designed for a single room and have one outdoor condenser matched to one indoor head. Indoor units can come in various styles, such as wall mounts, floor mounts, ceiling cassettes, and mini-ducts.
Multi-zone systems (bottom) allow you to heat or cool individual rooms with multiple indoor coils connected to one outdoor condenser. These systems create flexible ‘zones of comfort’.
Heat Pump Water Heater
A heat pump water heater is essentially an electric water heater with an air source heat pump on top. They use indoor air to heat the water and usually have a backup system to meet high demands.
These heat pumps work like a refrigerator, but in reverse, pulling warm air from the surrounding area, heating it, and then transferring it to the tank to heat your water.
Heat pump water heaters can be 2-3 times more efficient than their conventional counterparts and have lower operating costs as well.
