Health Central » Heat Pumps

HVAC – An Introduction to Central and Local Heating and Cooling Systems

admin — Thu, 10 Dec 2009 06:01:51 +0000

Heating, ventilation and air conditioning (HVAC) in the home has a few principal functions. These principles include controlling the temperature, the humidity, and maintaining the atmosphere quality. Heating and cooling systems are classified into two groups: Central and local systems.

Central System

The central system is the most standard method for controlling the temperature in the home. It produces warm or cool air in one central area and then distributes it throughout the house. They may be either radiant or forced air. It is most commonly a central AC unit, as well. Some examples of central HVAC schemes include heat pumps, gas and oil furnaces, evaporator coils, and air conditioners.

Heating Using Central System

Heating units provide welcomed warmth to the home especially in cold climates. They are either radiant or forced air heating systems.

Radiant systems work by transferring heat from heated water or steam that is circulated through an arrangement of radiators or exchangers. The radiators transfer heat to the area or room by convection and not radiation.

Forced air central heating operates by heating an exchanger (usually a furnace) either by hot water, gas, electricity or oil. Air is forced to pass over or through the exchanger that warms the atmosphere. The hot ventilation circulates through sheet metal ducts which run into each room or area by registered vents.

Some typical warming products include heat pumps, gas and oil furnaces, fan coils, and broilers.

Cooling Using Central System

The central system used for AC relies on ducts to deliver the cooled ventilation throughout the home. The AC provides cooling, ventilation, humidity control, and even heat (if using a heat pump). Typical AC uses refrigerants such as Puron or Freon to distribute the cool breeze into the duct work.

The AC unit is placed outside the structure in the proximity of the furnace or boiler since the cool breeze circulates through the same ducts as the warm breeze. This sends a large amount of heat to the outside atmosphere.

The cooling unit helps control the humidity in the home by dehumidifying the atmosphere. This is important since mold is a major health concern in homes. The warm breeze that passes over the indoor evaporator coils does not hold as much moisture as when carried at higher temperatures. The extra moisture condenses on outside of the coils, and it is taken away through a drain. The process takes away the extra moisture relieving the area from mold.

AC homes often have sealed windows because the open window disturbs the control scheme from keeping a constant temperature in the structure.

Some central cooling units are central AC, heat pumps, and evaporator coils.

Local Heating and Cooling

Local heating and cooling schemes produce hot and cool air at the location where it’s needed and serves small spaces well. It gives immediate results to the area. It doesn’t circulate throughout the entire structure.

Some examples of local units include window air conditioning units, wood or pellet stoves, space heaters, and sometimes baseboard heat if installed in a room or area which uses its own thermostat.

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Environmentally Friendly Way To Heat Your Home

admin — Tue, 17 Nov 2009 16:44:16 +0000

In this environmentally friendly world that we all live in certain steps have to be taken to ensure that there is still a world for people to inhabit in the future. People all over the world are looking at ways to help save energy and the world’s resources. Household heating is a major consumer of energy so whatever can be developed to reduce the effect on the environment has got to be a step in the right direction.

By extracting heat from the ground or air (geothermal energy) and then compressing it to raise the temperature significantly, the heat generated can then be used for water or space heating.

Since there is quite a lot of heat energy in even very cold materials, heat pumps can use sources that appear to be very unpromising. For example, if the temperature of the air is 5°C, that might appear to be too cold to extract any heat. In reality 5°C is pretty hot compared to absolute zero (-273°C) and therefore an air source heat pump can produce useable heat all year round. Think of your deep freeze. Heat continues to be extracted from that area even though it’s well below freezing.

Heat pumps can use air, water and, increasingly commonly, the ground below your feet as a source of energy. Ground water is a particularly useful source of heat since it rarely gets much colder than 7°C.

Unlike more conventional heating or air conditioning, heat pumps minimise pollution and fuel use. By utilizing entirely free and renewable geothermal sources of energy they are very low carbon and very economic to run. During hotter summer months the latest models can even be run in reverse to passively extract heat from inside a home and ‘dump it’ into the ground. This method of cooling is one of the lowest carbon and lowest energy approaches available.

For every unit of electrical power needed to extract the heat, up to six units of heat can be obtained. That’s right, heat pumps can be up to 600 per cent efficient. It’s like buying a low-energy light bulb with an output rating of I00 watts but with an energy usage of only 20 watts. Remember, we spend very little on electricity for light bulbs in our homes compared to running our heating and hot water systems – so the savings are much greater.

The attraction of running a heating system this efficiently is obvious. It saves money and makes a real contribution towards a low or even zero carbon building and towards reducing the devastating impact of climate change. It’s worth recalling how, by 2016, every new home in the UK will need to be rated ‘zero carbon’. Given that the law in this area is getting tougher all the time and the 2016 date is now fixed, new business opportunities are growing rapidly.

More and more heat pumps will be installed in the coming years which can only be good news for the environment. Pioneering companies have already gotten to grips with issues around the ground works required and enterprising trades people are discovering how they can become part of the future of our industry.

The next generation of heat pump technology that is even easier to install, and operate further reduces running costs and improves the already impressive efficiency which will make the models of the future even more appealing to the mass market. These will offer air, water and ground source heat pumps to suit all household heating needs, helping to reduce the cost of heating water for your bath as well as heating the whole house during the colder months. In addition to being powerful systems in their own right the heat pumps of the future even come ready to connect to a solar heating system, complete with flat-panel collector array and solar cylinder, providing an integration of solar energy and heat pump for domestic hot water and central heating.

Heat pumps will make a huge difference to the way we heat our homes as well as making a big difference, for the better on the environment.

By: Harwood E Woodpecker

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Adding Central Heat and Air to an Existing Home

admin — Sun, 01 Nov 2009 21:38:32 +0000

Many older homes were built pre-central heat and air. This is a luxury that many of us have to enjoy and when moving into an older we find that this luxury is also a necessity. We tend to lose tolerance for heat as we grow older and those old window air conditioning units just look tacky. However, the whole idea of having to add ducts to a home can sound difficult and expensive, but it is easier than you might think.

Central heat and air uses a primary heating appliance such as a furnace that is often located in an area such as a small closet, basement or garage. These systems deliver heat throughout the house through pumped warm air through a system of air ducts or by sending hot water or steam through pipes to room radiators. In newer homes, the system is usually built in with the home. The duct system may be set up with an air conditioner, heat pump, or furnace. There are also two types of systems including a forced air system and a gravity system. Gravity systems, however, do not provide air conditioning and can only provide heat. If your system includes an air conditioner, then the system is a forced-air system.

Air conditioners and heat pumps are forced air systems that share ductwork. The air conditioner runs on electricity and removes heat from air through refrigeration. The heat pump is capable of providing both heating and cooling. In the winter, the heat pump extracts the heat from outside air and delivers it into the home. In the summer it does the opposite. It extracts the cool air and pumps it into the home. These systems tend to be very economical and use only one duct system.

Many central air conditioners are split systems with a condenser outside and the fan and coil unit mounted in the attic. This means that the ducts will originate in the attics. The challenge here is if the home is two stories. It can be difficult to get the supply and return ducts to the first floor. The second floor will generally have ducts that run through the attic floor, while the first floor will need to have ducts run through closets. This takes up less space than some may think and the mess can be minimal. The contractor will need to cut holes in the first and second floor ceilings and some second floor closets will need to be used for running ducts.

This work will be well worth it in the long run when your home is kept cool in the summer and warm in the winter. If you have an older home, especially one with two stories, it can be difficult to spend anytime upstairs during the summer. The upstairs rooms will hold a large amount of heat and will definitely benefit from central heat and air. In the winter it is often difficult to keep first floors warm because the heat rises. Central heat will make your first floor rooms much more comfortable.

By: Christopher Brown

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Radiant Heat Panels: Red Hot Retrofit

admin — Sun, 01 Nov 2009 13:25:10 +0000

Red hot as in sales, that is. The reasons behind the increasing popularity of radiant heat panels are ease of installation, quick warm up, dust free heat, and low cost relative to other retrofit heating systems.

For the same price as a pellet stove, you could heat a 1,500 square foot home and not have to deal with locating, storing and lugging 40 pound bags of wood pellets.

A U.S. Department of Energy sponsored study found that radiant heat panels were 52% less expensive to operate than electric baseboard heat and 33% more cost effective than air to air heat pumps. The study concluded that “energy savings would be obtainable in a great portion of U.S. households”.

Radiant panels are about 1 inch thick, and range in size from 2’x2’ to 2’x8’. They are textured to look like the ceiling and can be painted to match the room’s decor with a quality water based acrylic paint.

The panels operate at 150-170 degrees F. and radiate heat to objects and people in the room. The panel itself reaches operating temperature in only three to five minutes.

Advantages of Radiant Heat Panels

Heat loss from ducts, even insulated ones, reduces the efficiency of forced air systems. Additional leakage is created by the internal air pressure generated by forced air systems. No ducts, no pressure, no leakage problems.

Since the need for a blower to circulate heat is eliminated, so is the cost of electricity to run the blower motor. Without a blower, there are no filters that need to be replaced.
Heating without moving air also eliminates drafts and prevents dust and pollen from circulating while maintaining the air’s moisture content.

Radiant heat panels require no maintenance or service because there are no moving parts.
With separate thermostats for each room, zoned heating is easy as turning a light switch on and off. Significant energy savings can be realized by allowing only the occupied areas to be heated. The quick response time of radiant panels will return an unoccupied room to a comfortable temperature in minutes.

Radiant Heat Panel Applications

Radiant heat panels are an excellent source of heat for bathrooms (no more foggy mirrors), log homes, gazebos, screened in porches and stables. If you’re heating a greenhouse, radiant heat will protect your plants in the absence of sunlight by maintaining root temperatures.

Replacing a wood stove with ceiling mounted panels in auxiliary buildings such as workshops or studios allows the use of all available floor space.

Radiant Heat Panel Installation and Cost

The low amperage requirements for ceiling heat panels can usually be provided by existing 120 or 240 Volt circuits. The 30%-70% wattage reduction over electric baseboard heating eliminates the need for dedicated wiring. Wherever a single panel is installed, the existing 120-volt capacity circuit is usually adequate for the additional load.

Installation of radiant heat panels typically costs between $1.25 and $1.50 per square foot of heated space. For a 1,500 sq. ft. house the estimated cost would be $1,900 to $2,300. That’s considerably less than the cost for a complete forced air system.

Disadvantage of Radiant Heat Panels

The major limitation of radiant heat panels is the absence of a cooling function. Installing a ducted central air conditioner would undermine many of the advantages of using radiant panels.

One way around this would be to install a mini-split air conditioning system. The mini-split, like radiant panels, is also a cost effective retrofit solution and can be zoned to cool only occupied rooms.

If controlling heating costs is your primary concern, radiant heat panels offer an easy, cost effective and healthy way to retrofit your home with comfortable, reliable heat.

By: Sam Streubel

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