How To Look At A House

McGarry and Madsen's home inspection blog for buyers of  

site-built, mobile/manfuactured and modular homes

How can I tell the age of a Day & Night heat pump or air conditioner from the serial number?

Wednesday, May 20, 2020

The second two digits of the serial number are the year of manufacture of a Day & Night heat pump or air conditioner. This unit was manufactured in 2002.

    For units from the late 1960s thru the late 1980s, there is a different serial number code, with the single number after an initial letter being the year of manufacture. So the serial number of the unit below indicates it was manufactured in 1978. Because the “8” may be for 1968,1978, or 1988, you want to look at the ANSI certification year, or year of construction of the home, for guidance. This home was built in 1979, so we determined it that way. Whatever year your figure out, it’s a really old system.

    To find out the age of another brand of air conditioner or heat pump, go to How do I determine the age of my air conditioner?,  which has a listing of all major manufacturers and links to instructions for decoding their serial numbers.

        Also, see our blog posts What size in tons is my Day & Night heat pump or air conditioner? and How can I find out the SEER of my air conditioner? 

    And to figure out what all the other numbers listed on the condenser data plate mean, go to our blog post How do I understand the air conditioner or heat pump condenser label (data plate)?

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  To learn more about heating and air conditioning systems, see these other blog posts: 

My air conditioner won't turn on. What's wrong? 

How can I find out the size of my air conditioner? 

Where is the air filter for my central air conditioner and furnace? I can’t find it? 

Does an old air conditioner use more electricity as it ages? 

How did homes stay cool in Florida before air conditioning? 

What is wrong with an air conditioner when the air flow out of the vents is low?

Why has the thermostat screen gone blank? 

Why does it take so long to cool a house when an air conditioner has been off for a while? 

Why is my air conditioner not cooling enough? 

What are the most common problems with wall/window air conditioners?  

Will closing doors reduce my heating and cooling costs? 

   Visit our HEATING AND AIR CONDITIONING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

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