|
SPACE HEATING : Direct Hot Air Heating, Heat Pump Preheat, Air Radiant Floor Heating
WATER HEATING: Water Preheat
EQUIPMENT HEATING: Clothes Dryer Air Preheat, Heat Pump Heating
COMMERCIAL: Industrial, Commercial, Agricultural
How to Use Your Heater Boards for Clothes Dryer Preheating
Clothes dryers use about 5% of all the energy used in a home. Usually, they are electric dryers which use electric resistance heat to warm the air in the dryer. Electric resistance heat is one of the most expensive forms of heat. So, running the dryer for a few hours per week can add a few hundred dollars to the annual household energy bills.
In addition to using heat within the dryer itself, clothes dryers also pull heated air for the house and exhaust it out the dryer vent. Heated household air goes in the dryer air intake and out the dryer exhaust vent. A typical dryer air flow is about 150 cubic feet per minute. That is 7,500 cubic feet of air per hour. After 2 hours, a clothes dryer will have pulled all the heated air in a 2,000 square foot house out through the dryer vent.
Solar Air Heating Clothes Dryer download .pdf
If that is the case, then how come there is still warm air in the house after the dryer has run for a while? In fact, how come there is any air at all? The reason is that outside air is leaking in to fill the vacuum created by the dryer blowing air out of the house. The cold outside air leaks into the house from a variety of openings, cracks, and leaks in the walls, floors, bathroom vents fans, oven vent fans, leaky windows and doors, leaky chimney dampers, etc.
You may feel the effects as cold drafts throughout the house as the air moves in and blends with the warmer air in the house. After a short time you will also feel the effects when you hear the furnace/boiler/heat pump turn on to heat all the cool air now filling the house. So running the clothes dryer not only uses energy in the dryer, it also uses energy to heat the cold air entering the house.
However, if solar Heater Boards are put to use to preheat a supply of air for the clothes dryer, then you will save energy in two ways: dryer heating energy and house heating energy. The warm solar heated air can be delivered to the area of the dryer air intake. This will minimize the heating by the electric (or gas) heater in the dryer, as it raises the dryer air temperature toward the dryer setting (high, medium, low, etc). It will also eliminate household heating caused by the cold air leaking it to supply the dryer air. Eliminating the cold air leaking in around the house, reduces the time the furnace/heat pump/boiler needs to run to keep the house warm. Even if the solar heated air is only 60 degrees, on a 20 degree day, it will ease the burden on the heating system which would otherwise have to overcome 20 degree air entering the house.
To use this approach, the solar heated air should be discharged “in the area” of the dryer air intake, which is typically in the bottom near the back or side of the dryer.
DO NOT CONNECT THE SOLAR AIR DUCT DIRECTLY TO THE DRYER INTAKE
The dryer must be able to pull air from the room at all times. Terminating solar air duct at floor level …WITHIN A FEW FEET OF THE DRYER AIR INTAKE …..is acceptable. In this location, the solar heated air will flood the area around the dryer air intake with warm air. Whenever the dryer runs, it will pull as much warm air as is available into the dryer air intake. If the solar air supply is not available or slightly less than the dryer air flow, the dryer will pull as much additional room air as it needs to achieve its proper air flow.
NEVER RESTRICT THE AIR FLOW TO THE DRYER OR COVER OR BLOCK THE DRYER AIR INTAKE IN ANY WAY, AS IT CAN CAUSE OVERHEATING AND START A FIRE.
IF YOU HAVE A GAS FIRED OR PROPANE FIRED CLOTHES DRYER YOU SHOULD HAVE A QUALIFIED PLUMBER OR APPLIANCE INSTALLER CONFIRM THAT THE ARRANGEMENT OF THE SOLAR AIR SUPPLY IS ACCEPTABLE.
IF YOU HAVE ANY QUESTIONS ABOUT PROPER OPERATION OF A GAS APPLIANCE IN THE SAME ROOM AS THE SOLAR AIR SUPPLY, CALL A QUALIFIED PLUMBER OR APPLIANCE INSTALLER.
During the summer months, the solar heated air may be all that is necessary to achieve proper clothes drying temperatures. So you may be able to set your dryer to a no heat setting and simply let the solar heated air do the drying. This may take longer but you will save more energy. During those summer months you may wish to operate the solar fan manually whenever you turn on the dryer. If the fan operates automatically, you may wish to install a manual damper in the solar duct that will divert the solar heated air flow out of the house when the dryer is not operating but which can redirect it to the dryer intake when the dryer is operating.
| 
