Forced Air Unit (FAU)
FAU heat sources are the central furnaces we are so familiar with today. Next to fireplaces, these are the most common type of heat for the American house. The main energy sources for FAUs are either natural gas/propane or electricity. The heat generated by the source is transferred to air in a heat exchanger, then the hot air is blown through ducting to the various rooms of the home.
No leaks allowed
To work effectively, the ducting the hot air moves through must be well insulated and sealed tightly. If there are leaks anywhere in the system, the efficiency and quality of the conditioned air is massively degraded. The duct runs for these systems are normally in the attic or crawlspace. As a result, leaks in the ducting are not visually
apparent and can go for years unnoticed. Older systems tend to be leakier than new. Pressure testing the ducts is needed to reveal any defects.
How they work
Efficiency of the gas and propane furnaces have improved dramatically over the last 10 years. FAU’s are equipped with a blower system that circulates air from inside the home (through an opening called the “cold air return”), filters it, heats it, then redistributes the conditioned air through the ducts back to the various rooms.
Dampers are used to control the volume of air moving through the individual ducts from the furnace to rooms. The dampers are used to “balance” the heat evenly throughout the house or to cut off heat completely to certain areas where it may not be needed.
Sizing of systems
Smaller homes (less than 2000 sft) usually have a single FAU system. Homes larger than 2000 sft, may have a second or even third system as necessary to meet the needed footage and volume.
Heat registers are the vents in the individual rooms where warm air is distributed. Homeowners should experiment with the adjustable registers to establish the best heat flow for each room. Though not made for this, you can use the register to slightly reduce or increase the air flow to certain areas. For maximum comfort and efficient energy use, arrange furniture and draperies to allow unobstructed air flow from registers and to cold air returns.
It is importance to maintain adequate humidity levels in your home during the dry winter months. To do so your home may have been equipped with a whole house humidifier. If you have one, it will reside on the side of the main cold air return duct located next to your furnace. Without adequate humidity you may experience cracks in your wood floors, trims, cabinets and sheetrock. You may also experience health related issues such as sore throats, nose bleeds and static shocks, all associated with dry air.
Adjust the settings with changes in outdoor temps
Fluctuations in outdoor temperatures will require you to adjust the humidity setting. If not you could experience excess moisture, which can be just as damaging as dry air. The humidistat controls the amount of moisture being added to your home. It is important to understand that the appropriate humidity level in your home changes with the outdoor temperature. There is a chart on the face of your humidistat showing this relationship of suggested humidity levels to outside temperatures.
If you maintain humidity levels in the proper range, you should not experience any problems or discomfort.
Although humidistats play an important role, it is a bit unrealistic to expect the average homeowner to manage the system properly. In my humble opinion it is time for manufacturers of these devices to come up with a “smart” version. A smart device that will automatically sense and adjust for temperature and humidity changes as needed.
- Some newer high efficiency furnaces are equipped with combustion air piping to bring fresh air in from the outside to mix with gas to fuel the furnace flames.
- Never block the combustion air intake. Doing so will shut down the furnace and possibly allow combustion gas to enter the home.
- Some popping or pinging sounds are the natural result of ductwork heating and cooling in response to airflow as the system operates.
- The furnace system may emit an odor after being unused for an extended time. This is caused by dust that has settled in the heat exchanger and should pass quickly.
- No heat: Check your setbacks and thermostat. Wait 30 minutes as some furnaces have a reset timer. If the thermostat is working but still no heat, check the switch at your furnace, then your gas valve, then your circuit breaker. If those are all on, you likely have a pilot out or a failed igniter and may need a professional repair.
- 1x per year: Most newer model humidifiers used today include a disposable core that is easily removed from your system each year. Discard the core and replace it at the end of each heating season. This will improve air quality in your home during the upcoming cooling season and fall heating season.
- 1x per year: Change batteries in your thermostat.
- 2x per year: Clean any serviceable filters and change out the disposable filters. Also clean the housing, enclosure and the entire space around the unit.
- 2x per year: Remove the floor registers and vacuum out the body of the register as far as you can reach into the duct. Inspect the joint between the register boot and the flooring for any gaps, as well as the duct joints. Repair or seal as necessary.
- Every 5 years: Replace the igniter.
If your home contains a heat pump system, you should read the manual to be aware of the performance characteristics unique to these systems. A heat pump system operates differently from a gas-fired, forced-air furnace.
Heat pump systems are different
With a heat pump the same machinery provides both heat and air conditioning. This is possible because refrigerant flows back and forth in the coils of the heat pump, controlled by a reversing valve. In the heating mode, the heat pump removes heat from the outside air and transfers it to the inside air. In the cooling mode, it does just the opposite, removing heat from the inside air and discharging it outside.
Slower heating operation
With a heat pump system do not expect dramatic notable temperatures in the air coming from the registers as is common with other kinds of systems. The coils used in a heat pump system operate at lower temperatures than those common in a gas forced-air system. As a result, for example, in the heat mode, air from the supply registers will typically range from 85 to 90 degrees F. The registers will not feel hot, even though the air discharged is warmer than the air in the room by as much as 20 degrees.
Low temperature emergency heat
At extreme low outside temperatures, less heat is available for the heat pump to draw from the exterior air. So an auxiliary electric heat element will come on to maintain the temperature you’ve set at the thermostat. The auxiliary system will also come on whenever the temperature at the thermostat is moved 1.5 degrees or more at one time.
In the heat mode, the heat pump coils outside may dip below freezing temperatures. Moisture in the air will condense into frost and accumulate on the coils under these circumstances. The system will then go into defrost mode to clear accumulated frost from the coils.
This is a normal part of the operation of the system and will occur automatically. During defrost, the outside fan will stop temporarily. The defrost cycle lasts no longer than 10 minutes and may occur every 90 minutes as needed. Unless you have a night setback thermostat designed to work with a heat pump system, do not turn the thermostat down in the evenings.
- Taking good care of the furnace and heat pump systems can save energy dollars and prolong system life.
- Carefully read and follow the manufacturer’s literature on use and service. The guidelines here include general information only. Most HVAC contractors that install equipment offer maintenance contracts. Connect with them here.
- The furnace should have an on-off blower switch. This switch should be properly labeled. It looks like a regular light switch and is located adjacent to the furnace. When turned off, this switch overrides all furnace commands and shuts down the blower. This is usually done for safety purposes only when maintenance service is being performed, people have been known to accidentally turn the furnace off using this switch.
- 2x per year: Remember to change or clean the filter regularly throughout the year. A clogged filter can slow air flow and cause cold spots in your home. Although it takes less than one minute to change the filter, this is one of the most frequently overlooked details of normal furnace care. Buy filters in large case quantities for the sake of convenience and bulk pricing here. Store them in a dry place where you can get to them easily.
- 2x per year: If you have a permanent, washable, removable filter, you need to clean this at least twice a year or more in very dusty environments. Use water only to clean the filter, then air dry and leave unit off for a brief period to allow full drying. Do not use soaps or detergents on the filter.
- 1x per year: If you have an electronic air cleaner or a high efficient media air cleaner refer to manufacturer’s recommendation for cleaning and maintenance. When changing filters or performing maintenance yourself be sure reinstall any removed furnace panels correctly in order for the blower fan to operate.
- 1x per year: Inspect the furnace area and keep it sealed from the attic or crawlspace and vacuumed clean.
Ductless: VRV and Split Systems
A derivative of the heat pump system, ductless VRV’s and VRF’s have individual climate units located in each room. These climate units are then piped using special, small diameter lines that move warming or cooling liquid to a central compressor or inverter that is located outdoors.
Room x room systems
These systems allow each room to have individual control of their own temperature. For instance, one room can have heating on full blast while the room next door can have cooling. In addition to flexible temperature control, the individual heating and cooling units operate more efficiently as they deliver conditioned air directly from source into the room with no loss of heated air through leaks or broken joints as so frequently is the case with ducted systems.
One other advantage is space. Removing ducts running to and from each room frees up space in both attic and crawlspace. Relatively new to the US residential market, ductless systems have been in use commercially since the mid 1980’s in Japan. You have likely seen some of the early and less sophisticated models in motel rooms.
Today’s versions are sleek, quiet and can easily be adapted for use with any home design. Some systems today can have up to eight individual zones, each controlled by its own thermostat. Installation is much simpler and easier than conventional air handling systems. Most ductless systems, can be managed remotely using a smart phone, tablet or PC via the Internet to ensure optimal efficiency without sacrificing comfort. To help encourage the installation of energy efficient products such as these, many local utility companies offer significant rebates for the purchase of a ductless mini-split system.
Indoor units are placed in each room for individual heating and cooling. Each indoor unit operates independently to enable individual temperature settings.
Inverter technology has been described as cruise control for your heating or cooling system. It utilizes variable speed compressor pump to even out temperature fluctuations and reduce power consumption. Compressors only run as fast as they need to handle the cooling or heating demand. They can handle greater extremes in temperature, are smoother and more stable in operation, and reach the desired temperature more quickly than conventional air conditioners.
Benefits of Inverter systems:
- More heat at lower outdoor temperatures
- Lower pump RPMs = quieter operation
- Desired temperature in half the time
- Up to 30% more efficient
- Uniform temperature
- Make sure your unit has free airflow across the indoor cooling coil and the outdoor condenser.
- Turn off each indoor air handling unit, as well as the circuit switch for the outside unit. This will prevent an electric shock.
- Your system will need about an hour before cleaning to cool and return to a standing temperature.
- Check the immediate area around the outside unit. There should be ample room for unrestricted airflow to the cabinet, with 4 or more feet of clearance.
- 1x per week: In winter, when used for heating, inspect the system for ice and snow accumulation. Promptly remove any that you see.
- 1x per month: Clean the interior unit.
- 4x per year: Clean the air filter. Some models of ductless mini systems also offer indoor-air quality components that may need to be cleaned.
- 4x per year: Clean the cooling coil. The coil provides dehumidification, as well as cooling, which creates condensation. Check and clean the drain and inspect for any signs of mold and mildew around the components. If you do spot mold, the system will need a deep cleaning and treatment of the coil to prevent further contamination.
Centrally located air handler pushes air to each room. Air is sent through ducts from one central location to heat and cool all rooms. All rooms are air conditioned uniformly at the same temperature settings.
These systems provide my favorite type of heat. I love warm floors! They are nice to walk on and produce a cozy, all embracing warmth without the blowing of hot air in your face.
Warm floor types
There are two types of warm floor heating systems available, electric or circulating warm water. The circulating warm water type requires: 1 warm water, 2 a storage tank and 3 a complex series of valves and pumps to move the warm water to and through the appropriate cold floor.
If you have a low-cost way of producing hot water (boiler, solar panels, secondary heat from some machinery, geothermal etc.) this may be a good way to go, otherwise I have found the water systems complex, cumbersome and expensive. Electrical warm floor systems have evolved remarkably over the last few years and are now easy to install, efficient to operate, and effective at heating not only selected floors, but with the right insulation, the entire home.
Warm floors will cost a bit more and are slower to react to temperature changes. They work best as a set and forget system.
- 1x per year: If you have a hot water circulating system, it is best to have the original installer or a certified substitute professionally, inspect and check the operation of the boiler, pumps and individual valves during the off season and far prior to the winter operation time.
- 1x per year: Check and service any thermostat controls for either type system per the manufacturers recommendations.
Boilers are remotely located, heavy duty, water heaters that create mass amounts of very hot water for the purpose of circulating it to radiators that then transfer the heat to the air of the various rooms.
These machines create hot water only. If you want to store any of the heated water, you will need a separate insulated storage tank.
These systems are still used today in many commercial and institutional settings and some older apartment buildings but not so much in single family homes. If you have one of these boiler systems contact me and I will attempt to provide you with answers to your questions.
Fireplaces and Wood Stoves
These are basically radiators powered by burning wood, natural gas or propane. NOTE: Do not use anything for fuel not recommended by the manufacturer. Only use if you have functional smoke and CO alarms in the home.
Growing up in the 50s and 60s, dad always had a wonderful wood fire going in the big brick family room fireplace. It was fun to get up on cold mornings, still in pajamas, and stoke up the embers from the night before to get the new fire going. There was a huge pile of dry firewood stacked alongside the barn and a wheelbarrow full just outside the family room sliding door. One of my jobs was to keep that wheelbarrow full. So, with that childhood experience, I entered adult life a die-hard wood fireplace fan.
The gas option
But over the years, my attitude has changed. Firewood has become harder to get for one thing and finding a dry place to store it is harder still. Then there is the hauling of the logs through the house to be burned, and then hauling the ashes back out again. When we remodeled our living room about ten years ago my wife (who is much more practical than I), conspired with our designer to convert our beautiful wood burning fireplace into an even more beautiful gas fireplace. I had misgivings.
The change required the purchase of an appropriately sized pre-fabricated gas fireplace to fit into the old firebox. Then a gas line had to be run, and some new flue and combustion air ducts were installed. The new gas firebox had real-looking ceramic logs and was sealed over with a removable (for cleaning) glass face. It also had swinging metal screen doors just like my old fireplace. When it was all done, I had to admit that it looked fine and I was even more surprised at the heat it put out.
My new gas fireplace infatuation
About a year after the new fireplace was installed, I had serious spine surgery. I was laid up for more than a month over the Christmas and New Year’s holidays. I have to say that recovering in a recliner, next to that cozy gas fireplace was close to heaven. No wood to cut, no logs to handle or store, no ashes to clean up and the flames came on with a remote control.
Pellet or wood burning stoves:
These are the most efficient generators of heat from the wood burning platform. These metal boxes radiate heat spherically in all directions. Another key to efficiency is the ability to meter combustion air to the firebox in a way that allows control over the rate of burn. With pellet stoves all this is true plus you can also meter the speed of the fuel (wood pellets) being fed into the firebox. This allows for fine tuning the burn rate to match the need of the situation.
Open wood burning fireplace
Many still feel a real wood open hearth fireplace is an excellent way to create a warm, cozy atmosphere and I agree that for some applications like outdoor patios and fire pits wood fireplaces can still be appropriate.
However, for indoor applications, using a wood burning fireplace can result in inefficiently lost heat and wasted money if you are not careful. Only about 10 percent of the heat produced by a fire is radiated into the house. In most older homes, the heated air used by the fireplace for combustion sucks up the chimney and is quickly replaced with cold outside air drawn in through cracks around doors and windows.
Incompatible with “tight” homes
Newer homes are constructed so tightly that this does not happen. Instead a fresh air vent to supply the fireplace with combustion air is installed in the firebox and reduces the amount of heated air the fire draws from your house. The vent is located at the back lower edge of the firebox. Open this vent before starting the fire just as you would the damper. Keep the damper and cold air vent closed when not in use. Leaving these open is equivalent to having an open window in the house.
If you are done but the fire is still burning, temporarily use the glass fireplace doors to prevent heated air from being drawn up the chimney until the damper can be closed. Do not close glass fireplace doors over a roaring fire, especially if you are using hot-burning hardwoods (such as oak or hickory) because this could break the glass. Also, when closing the doors, open the mesh screens first. This prevents excessive heat on the mesh, which might result in warping or discoloration.
Building a fire slowly
Building a fire should be a clean, steady, slow-burning process. Begin with a small fire to allow the components of the fireplace to warm up slowly. Start the fire by preheating the flue with kindling or the log lighter, then add layers of logs stacked with air spaces between.
Remove ashes from under the grate when the fire is out and completely cool. Creosote and other wood-burning by-products accumulate inside the flue and spark arrester which can be a fire hazard. Hire a qualified chimney sweep to clean the chimney and fireplace once every season. Do not burn trash in the fireplace and never use any type of liquid fire starter.
Firebrick and mortar
Discoloration of the firebox is a normal result of use. Mortar/brick fire boxes may develop cracks due to temperature changes. Extremely high winds can result in a downdraft that may push smoke into the home. This condition should be rare and temporary. If you experience smoke on a regular basis a repair may be needed. In unusually heavy or prolonged precipitation, especially when accompanied by high winds, some water can enter the home through the chimney.
These heat sources can provide all the warmth and dancing flames of a wood fireplace without the wood, the smoke, ashes and popping sparks,embers or risk of carbon monoxide poisoning. All you have to do is push a button on the remote to turn on and off.
Be patient when lighting
Be patient with gas fireplaces, sometimes there is a slight delay between turning the switch on and flame ignition which is normal. The flames should ignite gently and silently. If you notice any deviation from this or any gas smell, immediately shut off the switch and call for repairs. High winds can cause a downdraft, which can blow out the pilot (on older models without an igniter), requiring you to relight it before using the fireplace.
If your fireplace is not coming on. Check the batteries in your remote and make sure the gas is on.
Most of these units have glass panels that can be removed and cleaned on the inside surfaces. Some of these are a bit tricky but read the manufacturer’s instructions and you should have no problems.
Types of Gas Fireplace Venting
These systems are sealed fireboxes with vent piping that transfers the combustion fumes and pollutants outside the home while bringing in fresh air for combustion. The vent can terminate on top of a chimney or on the exterior wall of the home. These fireplaces have a sealed pane of glass on the front of the fireplace.
Direct vent fireplaces are the most popular choice for homeowners because of their increased safety, efficiency, and versatility. They can be installed almost anywhere! A direct-vent fireplace will be 70%-85% efficient and are perfect for newer, air tight homes.
Natural vent (also referred to as B-vent)
These systems take in combustion air from inside the home and vent combustion fumes outside via a conventional chimney or pipe venting system through the roof. Some natural vent units have a sensor to extinguish the fire in case exhaust gasses ever reverse and come down the flue. These systems are less expensive to install but are also the least efficient to operate.
These are installed without venting at all. This allows them to be placed pretty much anywhere spacing and code allows. Without venting, all of the heat (including combustion gases) generated from the fire stays in the home. For this reason, vent-free systems can, in theory, be very efficient!
Because the combustion gasses stay indoors, vent-free units are designed to burn very cleanly. Unfortunately, without venting, any pollutants from the combustion process also remain in the home. The idea is similar to using a gas cooktop. These models come with sensors to automatically shut off the system if oxygen levels in the room become unsafe. See our article on the dangers of CO.
These systems are not intended for newer “tightly” constructed homes because they require fresh air for the combustion process to remain safe. Because there are many safer choices available, I do not recommend vent-free products.
These heating units are a less popular option for gas fireplaces. A fan-powered accessory is placed along the vent to boost the air exchange. This allows for longer vent runs. Power vented gas fireplaces can be installed where other types of fireplaces might not work, such as a freestanding wall.
Regardless of the venting option you choose, you must install a Carbon Monoxide detector in your home!