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Heating, Air Conditioning, Fridge, HVAC/Single speed vs two speed vs variable speed


Hi Chuck,

I am looking to upgrade my air conditioning units.  I have 3 of them and going to get Lennox ones.  I am in NJ where the summers aren't too hot but definitely do need some air conditioning on some days.  I'd say I use the AC for half of the summer.  

My contractor said to go with variable speed air handlers over single speed ones.  He recommended this one:

For the air conditioners, he recommended a single speed one since I don't use the AC that often:

Can a variable speed air handler work with a single speed AC?  Shouldn't it be paired with a variable AC unit?  I thought the variable air handler leaves the air flow on continuously so won't my AC unit be on all the time then leading to large electric bills?

Also, on the Lennox page:

They have units that say variable speed, multi stage, two stage and single stage.  What is the difference between variable and multi stage ones?

Thanks for your help!


Great question. The answer is "yes" ... a variable speed air handler will work with a single stage condensing unit. Basically, the condenser will deliver a certain amount of air to the a/h unit. A variable speed a/h will give you the ability to increase or decrease the speed/flow of the air that is delivered.

A 2 stage unit is like a car with 2 gears. Generally, a "regular" condenser operates at 100% capacity when it is on and your system is working to get your air temp down to the temp set on your thermostat. Once that temp is reached, the condenser shuts off (then comes back on after the thermostat rises a few degrees). A 2-stage condenser, instead of shutting off when your thermostat reaches the set temp, will "down shift" to about 60% capacity -- will keep the airflow moving, and delays the rise in air temp in your home (as opposed to the single stage which shuts off completely - then waits for the temp to rise a few degrees, then cuts back on and starts the cooling process all over again).

2 stage units are more expensive, BUT much more energy efficient and increases the level of comfort in the home during those cooling months. They MUST be paired with a variable speed a/h so that the a/h can adjust as the condenser adjusts from 1 stage to the other.

Lennox is a great brand. be sure and ask about the available warranties.... I recommend paying a little extra and getting the 10 yr parts and labor.

Hope that helps,


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Chuck Best


I can answer most fundamental questions about Air Conditioning and how it works. I can give advice on different services in the DFW area, as well as lend some advice as to pricing systems along with solid opinions as to quality equipment versus sub-standard equipment. I can help educate consumers with regards as to what to look for in a service company, as well as steps they can & should take when considering repairing vs replacing their A/C equipment.


I was the Sr. Sales Technician for one of the most well-established HVAC (residential) companies in DFW for over 5 years. I then became the Dallas Team Leader for another well-established DFW company based out of Ft. Worth. Became the Sales Manager for an area A/C business most recently.

I have written content for several area HVAC (residential) businesses with respect to their Sales Policy manuals. I personally wrote the Sales Training Manual for a well-established DFW area HVAC company.

BS Univ of NM 1985

Awards and Honors
Million Dollar Sales Club; 2009, 2010, 2010, 2011, 2012

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