Heating System F.A.Q.

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What is the best way to size my new furnace?



For a furnace replacement: The last thing you should do is replace your existing furnace with a furnace with the same input. Most existing furnaces are significantly oversized. An oversized furnace results in a more uncomfortable indoor environment with wide temperature swings, large temperature differences from room to room, and a significantly noisier heating system. If you are considering a furnace replacement, make sure your contractor carefully evaluates your application and performs a complete, accurate heat load in order to size your system.

For new construction, heat loads are typically much smaller than in the past. Make sure your contractor performs a room by room heat loss / gain to ensure that your heating and cooling system is properly sized in every room.

Bigger is NOT better when it comes to heating and cooling. Most heating systems are over-sized. An oversized furnace is noisier and less comfortable, louder, and less efficient. An oversized cooling system will also not dehumidify properly.

What type of heating system has the lowest operating cost?



In areas where it is available, natural gas is the most common way to heat your home. Typically older existing natural gas furnaces are 80% efficient or less. New natural gas furnaces have a minimum efficiency of 80%, and are commonly available with efficiencies well above 95%, which can save a significant amount of energy. In our area the cost per 100,000 btu's at 90% AFUE is $0.94. New heat pump systems offer costs / 100,000 btu of $0.92 with an efficiency of 10.0 HSPF, so heat pump systems are now a great choice too. Click here to learn more about your fuel choices and heating efficiencies. Mini split heat pumps, and geothermal heat pumps offer costs which are lower still so they are worth a look for sure.

What type of gas furnace do you recommend?



We recommend condensing Lennox gas furnaces. With efficiencies of up to 99% with variable speed blowers and wifi capabilities, they offer great value and comfort. In addition rebates are locally available for Lennox 90%+ gas furnaces from National Grid - our local natural gas supplier.

What is a variable speed blower motor?



A new Lennox gas furnace is available with a high-efficiency variable speed blower motor (ECM), or a constant torque motor. An ECM motor runs on direct current and can operate over a broad range of speeds. As speed drops, electrical consumption drops proportionally. They consume between 60 watts and 100 watts / hour, saving the average homeowner about $250 a year in electrical cost! Constant torque motors are higher efficiency than traditional PSC blower motors, but they are not as flexible as a true ECM motor.

What is furnace staging, and is a multi-stage or modulating furnace worth the extra cost?



Traditionally gas furnaces have been single stage: they are either off, or on, operating at 100% of their capacity regardless of the actual heat load required. Single stage furnaces cycle more, and tend to result in wider indoor air temperature swings and larger differences in indoor temperatures from room to room.

Two stage, or multi-stage gas furnaces operate at a lower output capacity most of the year based on either a multistage thermostat, an outdoor thermostat, or the onboard logic of the furnace control. When the furnace operates and a lower output level, the blower speed and heat output is lower, and the furnace will have longer, gentler furnace cycles. This improves indoor comfort and noise levels significantly.

Modulating gas furnaces can operate across a broad range of capacities based on the immediate needs of the building envelop. As the heat required changes, so do the furnace capacity. The result is significantly more comfortable and quieter operation, and often lower operating costs. Variable speed gas furnaces also make air conditioning better by allowing for the possibility of staged or modulating cooling, and much better dehumidification.

What is a heat pump?



An air source heat pump is like a traditional split air conditioning system, except that it is designed to work in both summer and winter to efficiently condition your home. In the winter months, a heat pump extracts heat from the cold outdoor air and transfers it indoors. In the summer, it pulls heat out of indoor space to cool your home. They are powered by electricity and transfer heat using refrigerant to provide comfort all year round.

What are the common types of heat pumps for residential use?



There are several types of heat pumps that are appropriate choices in our area:

  • Ducted air source heat pumps: Ducted split heat pumps have been a common choice for homeowners in relatively mild climates for decades. Traditionally they have required back-up or supplemental heat when the outdoor temperature drops to near or below freezing. Modern split heat pumps are now much more efficient and can operate efficiently well below freezing, but in colder climates will likely still need supplemental heat from electric resistance elements, or from a gas furnace as part of a dual fuel system.
  • Ductless mini split heat pumps: If your home does not have an existing duct system, or you are adding a conditioned space that cannot be served by your existing HVAC system, a ductless mini split heat pump is an excellent choice. An outdoor unit is combined with one, or as many as 8 indoor units, each with its own zone controls. Mini split indoor units come in a variety of configurations and typically do not require ductwork. In very cold climates, there are ductless mini split heat pump systems that offer rate capacity and efficiency well below 0°F and may not require any supplemental or back-up heating system.
  • Water source or ground source heat pumps: Also known as geothermal heat pumps, (GHPs) this class of heat pumps use the constant temperature of the earth as the exchange medium instead of outside air. Throughout our area, while outdoor air temperatures vary from very cold to extremely warm, ground temperature below a few feet remains virtually constant. Because of this constant temperature, GHPs are extremely efficient and do not require backup or supplemental heat on cold days. While GHPs are relatively costly to install they often offer the lowest ongoing operating cost.

Is a heat pump efficient?



Modern heat pumps are efficient for both heating and cooling operation.

  • Cooling efficiency is measured by SEER, or the Season Energy Efficiency Ratio. This is the ratio between the cooling output of an AC system seasonally divided by the energy consumption of the system. The higher the SEER rating the more efficient the system is. Lennox makes AC systems with SEER ratings from 13.0 to 26.0. Mitsubishi mono=split systems offer SEER ratings from 12.8 to 33.1.
  • Heat efficiency is measured in HSPF (Heating Seasonal Performance Factor) for air source heat pumps. This is the ratio of seasonal heating output divided by the energy input of the system. The higher the HSPF the more efficient the system is from heating. Lennox split heat pumps offer HSPF ratings from 8.2 to 10.2. Mitsubishi offers heat pumps with HSPF ratings from 8.5 to 13.0

Does a heat pump need a back-up system?



Traditionally a heat pump system requires supplemental heating capacity in areas with colder climates and temperatures fall well below freezing. Supplemental heating can come from a variety of sources but most typically come from electric resistance elements in the system air handler, or from a gas furnace for a dual fuel system. Supplemental heating is require because as the outdoor temperature drops the amount of heat required to maintain indoor temperatures increases, and the output capacity and efficiency of an air source heat pump decreases. The temperature at which the heat loss of the structure exceeds the output capacity of the heat pump is called the thermal balance point.

For cold weather ductless heat pumps, and ground source heat pumps designed within an efficient building envelop, a supplemental heat source may not be required because the structure never reaches the thermal balance point, even in the coldest winter weather.

What is a dual fuel system?



A dual fuel system combines and efficient air source heat pump, combined with a gas furnace. Dual fuel systems alternate between the heat pump and gas furnace based on the outside temperature for maximum efficiency.

What is a mini split heat pump?



Ductless, mini split heat pumps are a variable speed HVAC systems that are good add-ons to houses with "non-ducted" heating systems, such as hydronic (hot water heat), radiant panels, and space heaters. They can also be a good choice for room additions where extending or installing distribution ductwork is not feasible, and very efficient new homes that require only a small space conditioning system. The main advantages of mini splits are their small size and flexibility for zoning or heating and cooling individual rooms. Mitsubishi models can have as many as eight indoor air-handling units connected to one outdoor unit. In homes with smaller heating and cooling loads, mini split heat pumps can offer extremely efficient, environmentally sound indoor comfort.

How good is my furnace filter?



Almost all furnaces are shipped with a 1" thick filter. Its original purpose was to protect the furnace blower components from the accumulation of lint and dirt. A typical original furnace filter is made from spun fiberglass and does little more than preventing large dust particles, lint, and other debris from accumulating in your furnace and ductwork. You should definitely consider upgrading to a higher quality replacement filter.

What is the MERV rating of my furnace filter?



Furnace effectiveness is measured by the MERV (minimum efficiency reporting value) rating. The higher filter MERV rating, the more efficient it is at trapping particles. A typical 1" fiberglass filter has a MERV rating of 2-3. The highest MERV rating is 20. Other filter types:

  • Disposable pleated filters made of polyester or cotton paper. MERV rating: 6. Can remove some small particles like mold spores, but need to be changed frequently.
  • Polyester: This reusable filter is denser than fiberglass, so it blocks more airborne particulates, and it comes in either a flat or pleated version in thicknesses up to four inches. MERV rating: 8.
  • Electrostatic: A electrostatic filter contains self-charging electrostatic cotton or paper fibers that attract and trap small particles. MERV rating: 10.
  • 4-5" High efficiency pleated filter: Synthetic cotton within a tight leak resistant frame. MERV rating 14-16.

Will my furnace filter remove black mold or the covid virus?



Properly maintained media filters do a good removing dust, lint, pet hair, and some mold spores from the airstream. However they are ineffective and removing the smallest particles like bacteria and viruses, and smoke particles down to 0.01 micron. Electronic filters, combined with media pre-filters, can remove these smallest particles effectively.

Will my furnace dry out the air in my home in the winter?



The colder a given volume of air is, the less able it is to retain water vapor. So the wintertime air outdoors has much less moisture in it than either indoor air, or summertime outdoor air. An indoor environment can dry out when cold outdoor air migrates inside effectively reducing the relative humidity to uncomfortable levels. If your furnace uses interior air for combustion, this causes lower indoor air pressure and increases the amount of outdoor air drawn into the conditioned space to replace the air being discharged with the flue gases. The use of vented kitchen fans (without make-up air), or wood burning or chimney vented gas fireplaces can also sharply increase the drying effect of winter air infiltration. A sealed combustion furnace, which draws combustion air from outdoors would eliminate this problem.

How often should I change my furnace filter?



A rule of thumb is every 90 days, or in temperate climates at the start of both the heating and cooling season. This can vary based on your family and lifestyle, and the type of filter your system has. If you have pets, or active kids you will likely find the need to change your filters more often. If you have a higher MERV rated media filter it may clog more quickly and require more frequent changes.

How often should I have my heating system professionally serviced?



All furnace manufacturers recommend that your furnace is serviced every year by a trained HVAC professional. If used as part of a cooling system, it should be serviced in both the spring and the fall. Annual maintenance, including a thorough examination and cleaning of the parts that commonly malfunction, like the air filter, the fan, the vent, and the heat exchanger, will ensure safe operation, prolong equipment life, and sharply reduce the possibility of unanticipated failures.

If my furnace isn't running, can I fix it myself?



There are things you can check if your furnace does not turn on properly:

  • Check your fuel: If you have a gas furnace, make sure that the gas supply is turned on both at the meter, and at the furnace.
  • Check your thermostat: Make sure your thermostat is "ON", is set to "HEAT", and the desired room temperature is set higher than the current ambient temperature.
  • Check your furnace power supply: Check your circuit breaker panel to ensure that your heating system breaker is "ON". Check your system emergency switch to ensure that it is on. This switch is typically a traditional toggle switch that may have a RED cover-plate near the entry to your utility space.
  • Check your system air grills and registers: Ensure that both your supply and return air registers are free of obstructions.
  • Furnace filters: Change your furnace filter and re-start your furnace.

Can my new furnace vent into my chimney?



Most new 80% gas furnaces are vented in a properly sized B-Vent or masonry chimney that terminates through the roof. Make sure you consult with a licensed heating professional to make sure your existing chimney is in good condition and appropriately sized for the load. Condensing furnaces, or furnaces with rated AFUE efficiencies of 90%+, can NOT be vented into a conventional chimney because flue-gas temperatures are too low to properly vent. Condensing furnaces are typically vented with plastic venting like PVC either out the sidewall or through the roof. Condensation is produced as a by-product of combustion in condensing furnaces, and will need to be properly drained.

Can I control my heating system with my smartphone?



Yes. This can be done in three ways:

  • On selected equipment, like those with Lennox® iComfort® or Mitsubishi kuno cloud technology, you can enjoy advanced full system integration through their mobile app. These systems also enable contactless service tech integration and advanced control of other system components such as IAQ equipment.
  • Home automation platforms like Apple HomeKit, Amazon Alexa, or Google Home Assistant offer full heating and cooling integration with integrated system controls, and through the Apple, Alexa, or Google apps.
  • Many controls manufacturers now offer wifi enabled thermostats and controls, and companion apps that all world-wide home integration via your smartphone.