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HVAC Terms Made Simple: Manual J Load Calculation

Manual J load calculation is the gold standard in the HVAC industry for properly sizing a heating and cooling system. Bigger is not better when it comes to HVAC systems. Conducting the load calculation eliminates the risk of over-sizing or under-sizing it.

The load calculation determines how much cooling or heating your home will need when the weather is at its hottest or coldest. Homes with high levels of energy efficiency don’t need as much capacity, which helps you save energy and money.

What’s Involved

The load calculation involves going through your home carefully to evaluate and calculate how energy efficient it is. The HVAC professional will assess the insulation levels, air infiltration rates, and the heat gain or loss from the windows. They take into account the floorplan design and your family’s preferred temperatures and lifestyle.

The Manual J load calculation software returns a value that helps you and the technician arrive at the best size for your home. Manual J has sister software that helps the technicians find the best size and configuration for the ductwork. Ducts that are too small are noisy and those that are too large won’t have the air pressure they need to deliver the conditioned air at the required velocity.

The Benefits

A central HVAC system that has been sized carefully will last longer, give you more comfort and use less energy. When you oversize the new equipment, it’s much more likely to break down more often, drive up energy bills and provide less even cooling and heating.

When the system is too large, it starts and stops more often and runs in shorter cycles. Cooling equipment uses a lot of electricity when it first starts, which stresses the parts and drives up electrical bills. If it’s too small, the system won’t be able to effectively cool or heat your home during weather extremes.

If you’d like more information about the Manual J load calculation, contact Sherlock Plumbing, Heating & Air. We provide trusted HVAC services for North County homeowners.

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