MANHATTAN--Ask Energenie is produced by the Kansas Energy Extension Service through Kansas State University. Need some energy answers? Send your questions to: Ask Energenie, Rm. 133, Ward Hall, Kansas State University, Manhattan, KS 66506; or call 913-532-6026.
Can I improve my air conditioner's performance by spraying
the condenser coil with water?
Yes, however, precautions must be taken to avoid corrosion of
coils.
Spraying your condenser coil can provide a savings by reducing the condenser temperatures," said Dennis Matteson, extension specialist in small business energy at Kansas State University.
Because the condenser must release heat to the outside air, the condenser temperature rises as the outside air temperature rises.
When you spray the coils, the water evaporates at a temperature called the wet bulb temperature," Matteson said. "In Kansas, this wet bulb temperature is usually 15 to 20 degrees cooler than the air temperature during the hottest part of the year."
You need to observe several precautions before installing a condenser spraying mechanism, Matteson advised. Water high in calcium or magnesium may cause a buildup on the coil fin surfaces, and this will reduce efficiency. The buildup usually can be removed with an acidic coil cleaning solvent.
If you have hard water, a better solution may be to install an evaporative cooler pad designed for the intake air of the condenser," Matteson said.
If designed and installed properly, this type of system can provide approximately the same cooling effect with the added convenience of easy-to-replace pads.
My home is heated by baseboard heaters. Could I run cold water
through these in the summer for cooling?
Although baseboard systems are efficient for central heating,
it would be difficult to convert them for cooling," said
Richard B. Hayter, director of Engineering Extension at Kansas
State University.
There are two problems to overcome. First, the temperature difference between the cold water and the room air would be much smaller than the difference between hot water and room air in the winter. Thus, the rate of heat transfer from the summer air to the cold baseboard units would be low.
To remedy this, you'd have to increase the baseboard surface area enormously to provide more surface for heat exchange.
The second problem is that condensation would collect on the base-boards and drip onto the floor unless some kind of drain system were installed." Hayter said.
I need to purchase a new water heater. How do I determine the
size I need for my family?
"Water heaters have a 'first hour rating,' which is the amount
of hot water the water heater can supply in the first hour of
operation," said Doug Walter, extension specialist in residential
energy at Kansas State University.
Although residential water heaters often are selected on the basis of storage capacity only, the first hour rating is the most accurate factor to use in determining the size you need. This rating is a combination of how much water is stored and how quickly cold water can be heated to the desired temperature.
"To know what kind of 'first hour rating' you need, you must determine how much hot water your family is likely to use in a peak hour," Walter said.
Typically, one shower or one bath requires 20 gallons of hot water; hand and face washing, four gallons; shaving, two gallons; food preparation, five gallons; hand dish washing, four gallons; automatic dish washing, two gallons; and automatic clothes washing, 32 gallons.
"Determine how much water you will need for practical convenience during a typical peak hour, not the absolute worst case," Walter said.
An oversized water heater will waste energy because of its greater surface area for losing heat.
Can I use well water to cool my home?
Yes.
"Although well water can be used for direct cooling in homes, in many cases it does not equal the level of comfort provided by conventional air conditioning," said Richard B. Hayter, director of Engineering Extension at Kansas State University.
A conventional air conditioner not only cools the air but also dehumidifies it. Because the temperature of water leaving a well is often too warm to adequately dehumidify the air, your home may be cool but high in humidity. This can be improved by using an electric dehumidifier.
"If you use well water for cooling, the water typically will be run through a conventional cooling coil over which air from the house is blown by a fan," Hayter said. "The water then may be returned directly to the ground or used for watering the lawn."
If you plan to use well water, consider the additional cost to pump the water as well as methods for properly disposing of the water.
Is the cooling load on my air conditioner influenced only by
the outdoor temperature?
No.
"Although hot, humid outside air contributes significantly to the air conditioning load, some of the heat the air conditioner must remove is produced inside your home," said Richard B. Hayter, director of Engineering Extension at Kansas State University.
The energy consumed by an electric appliance or light eventually results in an equal amount of heat being added to your home.
For example, a 100-watt light bulb will produce 100 watt hours (341 Btu) of heat in one hour. A 1200-watt hair dryer produces an equal amount of heat during the time it takes normally to dry your hair. Other appliances such as electric ranges, ovens, refrigerators and dishwashers contribute an even larger amount of heat.
"We sometimes forget about the heat produced by the pilot light in the furnace. You may want to extinguish it during the summer," Hayter said. "Doing so will not reduce the life of the furnace as was once thought."
A water heater that feels warm also is contributing heat to your home and should be insulated to reduce the energy required for heating water and cooling the air in your home.
"Make sure your clothes dryer is vented to the outside so that the exhaust is not contributing both heat and moisture to your home," Hayter said.
Bathing also adds a considerable amount of moisture to indoor air if the moisture is not exhausted directly from the bathroom.
"You can ventilate your entire home with a whole-house fan when the outside air is cooler than the air in your home," Hayter said. "Remember that when drawing in outside air you may also be adding to the humidity in your home. Some judgment is needed when using a whole-house fan."
Using heat-producing appliances as little as possible will both save energy and reduce the load on your air conditioner.
Is there any insulating value in adding carpeting to a floor?
Yes.
"Carpet has an approximate R value of 1.5," said Doug Walter, extension specialist in residential energy at Kansas State University. "R value is a measure of resistance to heat flow."
Adding carpet to an uninsulated floor over a crawl space or unheated basement will raise the R value of the floor from 3 to approximately 4.5.
"Carpeting is not, however, a substitute for adequate floor insulation over unheated basements or crawl spaces where an R value of 19, is recommended," Walter said.
Carpeting also can improve comfort by acting as a barrier between bare feet and cold floors.
Carpeting should not be added to concrete floors with slab heating systems and those that are used for thermal mass in passive solar systems because the carpet will reduce the transfer of heat.
Last summer when I used my dehumidifier, the room seemed warmer and less comfortable. Do I need a new dehumidifier?
"The reduced comfort may be due to the way the dehumidifier was used rather than a faulty dehumidifier," said Gene Meyer, extension specialist in small business energy at Kansas State University.
A dehumidifier removes moisture from the air by cooling it below the dew point. During dehumidification, heat removed from the vapor in the condensing process and heat given off by the compressor are discharged back into the room. The air from the dehumidifier is drier but warmer than the room air.
"If you have the dehumidifier set to remove a lot of moisture from the room, the heat added by the dehumidifier may reduce the comfort level in the room because of the increased temperature," Meyer said.
This summer, try setting the dehumidifier so that it does not run as long and strive for a balance between a room that is either too warm or too humid, Meyer recommended.
Will I save energy by lowering the ceilings in my house?
"Lowered ceilings generally will not result in a significant
energy savings unless the ceilings are unusually high-12 feet
or more-and unless the lowered ceiling is insulated." said
Doug Walter, extension specialist in residential energy at Kansas
State University.
Although lowering the ceilings reduces the total exposed wall area of the home, the lowered ceiling must be insulated to prevent heat from being lost through the exposed wall area above the ceiling.
"If your house has a second story, little savings will result from lowering and insulating the ceilings on the first floor because heat 'lost' through the ceiling is 'gained' by the second floor," Walter said.
High ceilings actually can be beneficial in summer because they allow warm air to rise to the ceiling above the occupied area.
How effective is wood as a thermal storage mass in a passive
solar home or addition?
Being a typical construction material, wood can make up
a significant portion of the physical structure of a home-and
can contribute to the overall thermal mass. Strictly for storing
heat, though, wood is less effective than more dense materials
such as concrete, brick or water," said Bruce Snead, residential
energy specialist at Kansas State University.
"The performance of wood as thermal storage will vary according to its density, thickness, and exposure to sunlight. Hardwoods like oak require 10 to 20 percent less exposed surface area than pine or other softwoods. When compared with an area of concrete four inches thick, wood at the same thickness requires three times more exposed surface area to store the same amount of heat. At a one-inch thickness of both materials, you will need 1.33 times more surface area of wood," he said.
According to Snead, wood in direct sunlight is 1.75 times more effective than the same thickness receiving only reflected sunlight, and 2.5 times more effective than shaded wood heated by air movement only.
"In addition, some woods will tend to fade after constant exposure to direct sun," he said.
How can I reduce the humidity in my home?
"Air conditioners and dehumidifiers help reduce the relative
humidity," said Richard Hayter, director of Engineering Extension
at Kansas State University.
Because both consume energy in the process, it is to your advantage to reduce the amount of water vapor in your home.
Moisture enters your home from air leaking in from outside, from household activities, and from the soil below your house. These moisture sources can be reduced by keeping your house tightly sealed in the summer as you would in the winter, running exhaust fans while bathing, showering, and cooking, and by making sure rain water drains away from your house.
A dehumidifier can be an effective way to reduce excessive humidity levels in a basement, but because dehumidifiers also produce some heat, a properly sized air conditioner is the best way to reduce humidity and maintain comfort in a living area.
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