Page 39 - The Homeowner's Handbook 2017

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Mini-Split Heat Pumps Air-Source Heat Pump

Virtues
■ ■ Can provide Flue Warm
heating gases air to
and cooling house
■ ■ No need for a
chimney or
exhaust flue
■ ■ More fuel efficient Burner
than a fossil fuel
furnace or boiler
Caveats
■ ■ Not practical in Circulating
very cold climates Cold air fan
■ ■ Does not get air as return
hot as a furnace

HIGH-EFFICIENCY BOILER
Hot Water Wiz
UCTLESS MINI-SPLIT HEAT PUMPS, or MSHPs, A boiler burns oil, natural gas or propane to heat water. That heated
are a good heating and cooling option for homes water is then pumped through a system of pipes to radiators,
without duct systems. Mini-splits can supplement baseboard heaters or a radiant floor.
Dan existing wood stove or condition a new addition, A good boiler will offer efficiencies of 90 to 95 percent and will
and they are also ideal for super-efficient new homes. Mini- include many of the same technologies as a high-efficiency furnace.
splits have two main components: an outdoor compressor/ These include a modulating burner that matches the heat output
condenser and an indoor air-handling unit. A conduit, which to whatever the thermostat is calling for at the moment, advanced
houses the power cable, refrigerant tubing, suction tubing and heat exchangers to extract more heat from the same amount of fuel,
a condensate drain, links the outdoor and indoor units. MSHPs and the ability to recover heat from the exhaust gas by condensing
are quiet, efficient and flexible, and because there are no ducts, it. The resulting exhaust is cool enough to be vented out of a plastic
they are easy to install. Here are a few points to consider if you pipe. In the best cases, this condensing process can squeeze 10 to 12
are in the market for a mini-split: percent more usable energy out of the fuel.
■ Choose the Right Mode. MSHPs work best when
■
allowed to modulate. Using them in “on/off” mode not only AIR-SOURCE HEAT PUMP
compromises their efficiency, but will likely result in wide tem- Reverse Motion
perature swings and discomfort. A heat pump is basically an air conditioner that works in reverse to
■ Know Yourself. Because MSHPs don’t rely on ducting provide heat. The heat pump captures and concentrates heat from
■
to distribute air, be aware that your habits may affect tempera- one area, then releases it to another.
tures in different rooms. For example, if you tend to leave your In heating mode, the heat pump takes heat from the outdoor air
bedroom door closed all the time, it may be warmer or cooler and delivers it to the home’s distribution system. In cooling mode,
than the rest of the house. it reverses direction to work like an air conditioner, extracting heat
■ Build Efficiently. The number of MSHPs required to from inside the house and blowing it outside. In cooling mode, this
■
heat your home depends on its square footage, but also on your waste heat can also be used for water heating. The most common
home’s layout. A small, very efficient two-story house might type is the split system, which uses separate indoor and outdoor
be served by just one MSHP, but be aware that there may be units, but you can also get packaged systems that place everything
temperature differences between the two floors, even if you in a self-contained outdoor unit. While air-source heat pumps can
use distribution fans. offer efficiencies of 200 to 300 percent, they’re most efficient in the
■ Bigger May Be Better. Oversizing MSHPs—choosing southern part of the country. A backup electric or gas heater may
■
units rated for a larger house—is okay. Oversizing can even be needed when the outside air drops below a certain temperature.
be beneficial, since MSHPs modulate their capacity and reach Although different versions are made for forced-air and hydronic
their highest efficiency when running at the lower end of their distribution, the forced-air type is the most common. Heat pumps
capacity range. don’t get air as hot as a furnace or boiler, so may require more
airflow to maintain the same temperature.

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