What Is a Manual J Load Calculation | Maytag HVAC Blog

What Is a Manual J Load Calculation?

Did your contractor preform a Manual J load calculation?

What is a Manual J load calculation?

Tons? BTUs? What does it all mean? Sizing matters when it comes to a new heating or air conditioning system. Did your contractor properly size your new equipment before installing it in your home?

Rule-of-thumb measurements or basing the size of your new system on what you already have is not best practice. A contractor should preform a Manual J load calculation to determine the size of your new heating and air equipment.

But, what is a Manual J load calculation?

Simply stated a Manual J load calculation factors in the different characteristics of your home (such as square footage, position of your walls, building materials, etc.) to determine how much heating or cooling capacity your home needs. Air conditioner capacity is measured in tons and BTUs. Tons – in relation to HVAC – is not a measurement of weight. A ton in HVAC is defined as a measurement of capacity in relation to melting one ton of ice over a 24-hour period. One ton is equivalent to 12,000 BTU/h.

But, why does a proper load calculation matter?

An undersized or oversized air conditioner can have an impact on the comfort of your home. Undersized air conditioners never reach temperature settings, run constantly, dry out your air and may have a shorter life. An oversized air conditioner will go through a process known as “short-cycling.” When an air conditioner short cycles, it reaches your desired temperature too quickly. Sound like a good thing? Well, your air conditioner is responsible for more than just temperature. It is also responsible for removing enough humidity from your home’s air. When an air conditioner short cycles, it is not removing enough humidity, and an overabundance of humidity can make your home feel warm and encourage mold growth – yuck!

When your local contractor comes out to give you a quote, make sure they perform a Manual J load calculation before they determine your needed cooling capacity. If they say you don’t need one, this could be a red flag.

 

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