Ask Energenie

October 1999

Contents

1. How do I prepare my hydronic or steam heating system for winter?

2. What should be done to my whole house fan to prepare for winter?

3. I've heard about the hazard of carbon monoxide poisoning from a furnace. How can I make sure my home is safe from it?

4. The fan on our furnace runs constantly, even when the burner is off. Is this OK?

5. How should I prepare my air conditioner for winter?

6. This past summer my electric bill seemed higher than it should have been, and I didn't run my air conditioner much. Is it possible that my electric meter is recording more consumption than I actually use?

1. How do I prepare my hydronic or steam heating system for winter?

"To insure proper operating, the system should be checked at least annually by a qualified service technician," said Gene Meyer extension mechanical engineer at Kansas State University.

Checks should include inspection of the combustion chamber, testing of the safety equipment and possibly a water quality test. Although many hydronic and steam systems have operated for years without annual inspections, owners of such systems should be aware of some of the problems and hazards associated with water or steam systems.

"If the systems have operated for several years without adding any water, the water quality probably will be acceptable," Meyer said.

A water quality test would still be a good idea. By testing and treating the water to proper chemical levels, the system will last longer, and you will have reduced maintenance on valves, pumps and other mechanical circulating equipment.

"Some hydronic systems will have both high temperatures and low water cutoffs," Meyer said.

Some of the other systems, however, may have only a high temperature cutoff. This is to prevent the burner from operating when water temperatures exceed the boiling point.

"If this higher temperature limit fails and the system is allowed to continue burning and generating steam, the water boiler may be damaged," Meyer said.

All steam systems should have a low-water cutoff that prevents the water from getting too low in the steam boiler. This low-water cutoff drain valve should be opened at least annually - preferably monthly - to remove contaminants in the lower water cutoff valve and to test its operation.

"Water testing for both systems should be done by a competent chemical testing company, which should recommend proper treatment for the water," Meyer said.

Back to Top

2. What should be done to my whole house fan to prepare for winter?

"After the cooling season, turn off the fan's power supply and cover the unit with an insulating material to reduce heat loss," said Doug Walter, president of Kansas Building Science Institute, Manhattan.

"Most whole house fans are located in a hallway and louvers close when the fan is turned off. The louvers rarely seal adequately and additional covering is necessary," Walter said.

Before working on the fan, turn off the power at the circuit breaker or pull the circuit disconnect located near the fan.

"If you are not sure the power is off, turn on the fan switch and check to see if the fan turns," Walter said. "Tag the breaker or disconnect it as a reminder to remove the insulating cover before turning on the power again next spring."

The best covering for the fan is an insulated box, which provides insulation value and reduces air infiltration.

"Another option, though not as good, is to cover the opening with plastic," Walter said. "This reduces air infiltration but has little insulation value."

Back to Top

3. I've heard about the hazard of carbon monoxide poisoning from a furnace. How can I make sure my home is safe from it?

"First you need to install an electronic carbon monoxide detector in your home," said Doug Walter, president of Kansas Building Science Institute in Manhattan, "and then you need to take steps to minimize the risk that carbon monoxide will enter your home."

Carbon monoxide (CO) is a colorless, odorless gas that is highly toxic, producing flu-like symptoms at low levels of exposure and death by asphyxiation at higher levels and prolonged exposure.

A CO detector can detect very small amounts of CO in the air in your home and provide you with a digital display of the CO level in parts per million (ppm). It will also sound a loud alarm, similar to that of a smoke alarm, if the level exceeds a safe threshold.

"Every room that contains a combustion appliance should have a CO detector," Walter said. "This would include the kitchen if you have a gas range and any room with a wood stove or fireplace. Of course, one should be placed near the furnace and water heater if they use a combustible fuel."

To further reduce the risk of carbon monoxide poisoning in your home check your fuel-burning appliances.

"Make sure that all combustion appliances are properly adjusted and that the by-products of combustion are being vented to the outside," Walter said.

To make sure your furnace and water heater are properly vented, check each vent pipe that connects these appliances to the chimney. Look for corrosion, cracks or gaps between pipe sections. Also, be sure it extends from furnace to chimney at a slope of at least 1/4-inch per foot of length.

"For example, a 4-foot vent pipe should have an upward slope of 1 inch or more," Walter said.

Next, make sure the appliance is getting enough draft.

"With the furnace running, check the chimney's draft by holding a smoke source (an extinguished match works well) near the draft hood or diverter on the front or top of your furnace," Walter said. "The smoke should be drawn into the vent." Perform the same test with exhaust fans running, including the clothes dryer.

"If the smoke spills or backdrafts, then you likely have a problem with the furnace vent or with negative pressure in the area surrounding the furnace. You should call in a professional to diagnose and correct the problem," he said.

A properly cleaned and adjusted furnace produces very little carbon monoxide.

"A professional should inspect and service your furnace at least every other year," Walter advised. "Call a furnace technician any time you observe a predominantly yellow flame in the burners."

These recommendations apply to wood-burning appliances as well. Wood fires almost always produce carbon monoxide, so proper venting, cleaning and maintenance are especially important.

Finally, avoid the use of "vent-free" combustion appliances. Vent-free simply means all the by-products of combustion are dumped into the air inside your house - the same air you breath. Common vent-free appliances include space heaters and fireplaces.

Back to Top

4. The fan on our furnace runs constantly, even when the burner is off. Is this OK?

"No," replied Doug Walter, president of Kansas Building Science Institute in Manhattan. "A continuously running fan won't harm your furnace, but it wastes energy, and the air movement may cause personal discomfort.

Furthermore, it may indicate a more serious problem in your furnace's operation.

"If you are familiar with how your furnace works, you will be able to detect a problem more easily," he said.

A furnace should normally operate in this sequence:

• The thermostat senses the need for heat. The gas valve opens and the burner comes on and starts to warm the heat exchanger.
• The furnace fan comes on when the air temperature reaches 120 to 140 degrees. When the thermostat senses that the room temperature has reached its set-point, the gas valve closes, shutting off the burner.
• The furnace fan continues to run until the heat exchanger has cooled to 90 to 120 degrees, then shuts off.

If you notice your fan running constantly, first check the thermostat and verify that the fan switch is set to "auto" so that the fan runs only when the furnace does.

For the next test, turn the thermostat to its lowest setting. The burner and fan should shut off within a few minutes.

"If the fan continues to run, the problem may be a defective fan switch," Walter said. "It could be stuck in the 'on' position."

Another possible malfunction is that the furnace is cycling on the high limit safety switch. Set the thermostat back to the normal setting and observe the burner on the furnace to see if the burner turns on and off in short cycles while fan continues to run. The high limit safety switch shuts off the flow of gas to the burner when the temperature inside the furnace reaches the designated setting - usually 200-250 degrees. Gas flow resumes once the furnace has cooled.

"The safety switch may be doing what it's supposed to - shutting off gas flow when the temperature exceeds a safe level - but this indicates a problem with your furnace that needs to be corrected," Walter said.

An overheating furnace is a serious safety concern because it could result in a fire.

The major cause of a furnace operating on the high limit safety switch is insufficient airflow. This could be caused by blocked supply or return air registers, a plugged filter, a loose fan belt, a dirty fan or any combination of these.

Whether the fan switch is defective or the furnace is cycling on the high limit switch, you should call a furnace technician to diagnose and correct the problem.

Back to Top

5. How should I prepare my air conditioner for winter?

"You can reduce energy costs and extend the life of your air conditioner with a few simple maintenance procedures in the fall," said Richard B. Hayter, director of Engineering Extension at Kansas State University.

You can damage your air conditioner if you turn it on in cold weather. If it is cold enough, the refrigerant may be a liquid when it enters the compressor, which will damage the compressor piston valves.

"To prevent your air conditioner from being turned on in the winter, turn off the circuit breaker that serves it," Hayter said. "You can also remove or turn off the electrical disconnect between the condensing unit and the electric service line."

An electric heating element inside the unit offers some protection against liquid refrigerant entering the compressor.

This heating element, which continuously draws electricity, keeps the refrigerant in a vapor state.

"By disconnecting the outdoor unit, you will turn off this heater, eliminating the energy drawn when the air conditioner is not in use," Hayter said. "Turning off the air conditioner at the thermostat does not turn off the heating element."

You can take similar precautions with window units that you leave in place during the winter. Disconnect the unit at the electrical outlet, or shut off the circuit breaker or pull the fuse to the outlet.

"At least 24 hours before using the air conditioner in the spring, reconnect the air conditioner, turn on the circuit breaker or reinstall the fuse," Hayter said. "This allows enough time for the refrigerant to vaporize."

Protect the outdoor condensing unit from debris and damage to the condenser fins by covering the unit throughout the winter. Similarly, you should cover the exterior of the window unit to reduce heat loss from the house.

"Do not cover or disconnect the outdoor unit if it is a heat pump, which will operate in the winter," Hayter said.

If you leave your window unit up throughout the winter, tightly seal around the opening to minimize air leaks. In addition, you may want to remove the front cover on the indoor side of the window unit, cover it with plastic and then replace it.

"You can also temporarily insulate the front of the window unit to reduce heat loss," Hayter said.

Back to Top

6. This past summer my electric bill seemed higher than it should have been, and I didn't run my air conditioner much. Is it possible that my electric meter is recording more consumption than I actually use?

"It is possible that your meter is out of calibration, but it's unlikely that this would make a major difference in your utility bill because the variance is usually small," said Doug Walter, president of Kansas Building Science Institute, Manhattan.

Most utilities in Kansas replace their customers' meters every three to five years.

"If you think your meter is faulty, call your utility," he said.

"A representative will first check your current consumption against the past year or two to see if there is an unexplainable difference," Walter said.

If your utility company detects a potential problem, it can send someone out to test your meter by connecting a known electrical load to it and then clock it.

Some utilities will also conduct an energy audit of your house.

"A likely culprit of an unusually high utility bill is a major electrical appliance that is defective or operating more than you are aware," Walter said.

A typical refrigerator, for example, consumes about 200 kilowatt-hours (kwh) a month. If it is low on refrigerant or if the condenser coils are loaded with dust, it might be running almost constantly, which would boost its consumption to more than 500 kwh a month.

"If you bought a new refrigerator or freezer and kept the old one plugged in, you've added 100 to 200 kwh to your monthly electric consumption," he said.

Using a well for watering your lawn and garden can also rack up a lot of kilowatt-hours. A 3/4-horsepower well pump consumes about 1.5 kwh per hour of use.

Walter said operating the furnace fan continuously during the summer might be another reason for a high utility bill.

Some people leave their furnace fan on to create air movement. A typical furnace fan, however, uses about 800 kwh a month if you operate it continuously.

"It's better to let the fan cycle on and off with the air conditioner and use a portable fan to create air movement," he said.

"Don't rule out your air conditioner as the culprit of your high utility bill," Walter said.

A three-ton unit that removes 36,000 Btu of heat per hour will use about 1,300 kwh during a typical summer month.

Weather makes a difference on how much the unit will operate, but lifestyle also has a major effect. Keeping the thermostat setting low (below 78 degrees) or operating many heat-producing appliances, like a kitchen range, can make your air conditioner run overtime even in mild weather.

If you have an electric water heater, lifestyle can have even more influence on your summer electric consumption.

"Having guests or college-age children home for the summer can boost your hot water (and electricity) consumption significantly," Walter said.

| Back to Top | Home |

Ask Energenie is produced by the Kansas Energy Extension Service through Kansas State University. This material was prepared with the support of the U.S. Department of Energy (DOE) Grant No. DE-FG48-97R802102. However, any opinions, findings, conclusions, or recommendations expressed herein are those of the author(s) and do not necessarily reflect the view of DOE.