Metro Heating and Cooling, Inc.




 Furnaces and Heating

 Do these newer furnaces have pilot lights?  Most of the furnaces built today do not have a pilot light that stays lit all the time.  Spark ignitions and hot surface ignitions have eliminated the standing pilot in an effort to meet federal efficiency standards.  The newer systems operate well when they are properly maintained.

  Should I get a bigger furnace than I have now?  Probably not, if your old furnace properly heated your home.  Most of the older furnaces installed in homes in the metro area are already oversized.  If the existing furnace is older than 15 years, the newer furnaces with their higher efficiency standards can typically be downsized to take advantage of this efficiency advantage.  A properly sized furnace will last longer than one that is oversize

 I have air conditioning or I plan on adding air conditioning...Do I need a special furnace for A/C?  Most of the furnaces manufactured today are air conditioning ready, meaning they have a multi-speed blower motor and built in relays and terminal strips to accommodate A/C.

 What is a Two Stage Furnace?  Most manufacturers build single stage furnaces, several also build two stage furnaces.  A single stage furnace typically has a single speed blower and inducer motor and operates at a single fixed Btu. rate.  This furnace needs to be designed to properly heat the home under the worst conditions, like a week of sub zero highs.  Fortunately, most of the heating season is quite milder than that, with lows in the 30's or warmer.  Under these conditions, the single stage furnace is considerably oversized causing a loss in efficiency as well as comfort level.  A two stage furnace is designed with a 2 speed inducer motor, low speed and high speed heating blower motors and a low fire/high fire gas control valve.  Low fire is typically 60% of high fire.  For example:  If your home requires a 100,000 Btu. of gas to properly heat your home under those worst of conditions, your 2 stage furnace would have 100,000 Btu. when you really need it.  When your thermostat tells your furnace to turn on, the first stage of a 2 stage furnace starts.  The inducer runs at a reduced speed.  The low fire circuit of the gas control allows 60,000 Btu. to begin heating the house and when the heating blower motor comes on it will run at a quieter, more energy efficient speed.  Obviously, using 60,000 Btu. is less than using 100,000 Btu., therefore run times of the furnace will be longer.  These longer run times help the furnace to maintain higher efficiencies and provide added benefits, such as longer periods for your humidifier or air cleaner system to work their magic.  With these longer run cycles, air stratification or heat stacking is reduced because of better mixing of the air in your home.  The low fire run time can be controlled either by a multi-stage thermostat or by a built-in timer.  Typically, the furnace will run at low fire (60,000 Btu.) for up to 15 minutes, then switch to the high fire mode, with high speed heating blower and 100,000 Btu. of heat.  Under most conditions, low fire mode will satisfy the thermostat and shut off the furnace before the high fire ever comes on.  There is where the savings really add up.

 What is a Variable Speed Blower?  Why would I want one?  The variable speed blower is designed to properly adjust the airflow supplied your duct system during each mode of operation.  Standard furnace blowers are operated at low speed for the heating modes, with the highest speed for air conditioning and/or continuous fan operation.  Variable speed blowers have more than just a low, medium and high speed.  The variable speed blower will adjust itself to overcome restrictions within the airstream, such as an air conditioning coil.  They are ideal when used in zoned systems where there are ever changing variables of zones opening and closing.  They are quiet.  Another advantage of the variable speed is the reduced electrical cost of operation, particularly when used in a continuous fan mode.  The blower speed in the continuous fan mode can be adjusted to allow very quiet, economical operation and in this mode your air cleaner and humidifier are able to perform better.  You end up with less heat stacking, better humidity control, cleaner air and quiet, economical operation.

 What is the big difference between 80% efficiency and 90+ efficiency furnaces?  Most manufacturers build furnaces in two general configurations, 80% (non-condensing) and 90+% (condensing) efficiency.  The 80% efficiency standard is the minimum federal standard for residential heating equipment.  Flue gasses contain many compounds such as carbon dioxide, carbon monoxide, sulfuric and nitric acids.  What the flue gas has the most of, though, is water in the form of steam.  The 80% efficiency furnace is designed to prevent condensation when it is properly installed.  Most furnace systems are common vented with the home's water heater.  Most water heaters are non-condensing under normal conditions.  When common venting is required or when the existing metal venting is to be reused, the 80% configuration is most commonly used.  Condensing furnaces (90%+ efficiency) extract almost all of the heat from the exhaust.  As more heat is removed from the flue gasses, the products of combustion are cooled to the point that condensation occurs.  The condensate is caustic to untreated metal, ceramic, brick, mortar and concrete.  The venting systems need to be specially constructed to deal with the caustic nature of the condensate, usually of stainless steel or, believe it or not, PVC plastic pipe.  Most homes can be readily modified to take advantage of the 90%+ efficiency models, but not in all cases.  Sometimes, the 90+ is the best and least expensive option, but usually the 80% configuration is the least expensive choice for most retrofit situations.

 How much value does a new furnace add to my home?  How much can I expect to save by moving higher in efficiency?  What is the pay back for upgrading?  For the most accurate figures, consult  Their website has an easy to fill out form to calculate costs of operation, do comparisons with your old equipment and uses US Government figures to calculate what a new furnace can add to your property value.  The site mentioned is not affiliated with Metro Heating and Cooling, Inc. or

 Since these newer furnaces don't have pilot lights, they must be almost maintenance free, right?  Unfortunately, the newer furnaces require more than just changing the filter every now and then.  These newer furnaces have more circuitry and moving parts than the old ones.  This complication increases with the advances in efficiency of the newer furnaces.  Most of the manufacturers as well as most of the gas suppliers recommend furnace heating equipment be cleaned, serviced and adjusted on an annual basis.  If this service is neglected, you can plan on a service call.  Annual cleaning, service and adjustment will help ensure safe, clean, reliable and efficient operation.

 I change my filter at the beginning of every winter.  Is that often enough?   Maybe, if you have one of the high performance filters.  Some high performance filters are designed to need yearly service, some are designed to be serviced at the beginning of each heating and cooling season.  If you are using the less expensive poly fiber filters or an electrostatic filter, you should service the filter every month.

 What should I know about my furnace?  Obviously, you should know where it is, like in the basement, crawl space, attic, closet, etc.  You should know how to turn on the light and make sure the bulb works.  You should know how to turn off the electricity to the furnace, both at the furnace room and also at the circuit breaker in your electric panel.  You should know where to turn off the gas to your furnace as well as any other appliances in your home.  You should know where your electric panel and gas meter are located.  You should know where the filter is located.  You should know the make, model, serial number, warranty status and approximate age of your furnace.  You need to be aware of the service requirements of your furnace, air conditioner, air cleaner and humidifier.  You need to know how to operate your thermostat and change the batteries as needed.  You should have the telephone number to your gas and electric supplier.  You should have our phone number:  303-366-7868.


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Copyright 2007 Metro Heating and Cooling, Inc.
Last modified: 04/12/14