It is a common misconception that a bigger air conditioner or furnace is better than reducing the size of the existing system in your home. Most consumers feel that a larger air conditioner will deliver colder air – faster and save money because it will not run too long. This is also the case when we talk about gas furnaces. More capacity – to heat your home quickly. The truth is that most HVAC contractors will quote the existing capacity that is in your home instead of accurately determining the load an not concerned about fixing any comfort problems. They will only want to provide a free quote as quickly as they can, and present the least confusing options at the best price to win your business. This is a shortcut and will cost your family much more money up front and long-term in higher utility bills.
The old way doesn’t work anymore.
Today, HVAC contractors are under mandatory testing measures from the state of California. The 2013 Title 24 Required testing and verification protocols have been put in place to prove the efficiency of your homes heating and cooling system. Starting with Duct Testing – if your home’s existing comfort system was installed before there was a concern for energy efficiency then it is most likely grossly over-sized. Your duct system is most likely undersized to handle the new equipment rated at the same capacity. The reason is that today’s residential systems deliver comfort more efficiency, when they are right-sized. Your new system will most likely not pass the required measures unless the capacity is matched to the airflow that can be delivered through the existing duct system. If your new system is replaced based on the existing capacity you should consider having your contractor design a duct system that can handle the higher performance of modern HVAC systems.
Your existing furnace is over 25 years old and has a capacity of 100,000 BTU/HR @ 60% AFUE or less. Let’s say your new gas furnace is replaced with the same capacity, 100,000 BTU/HR with a minimum AFUE rating of 80%. This makes the new system 20% more efficient than the original gas furnace. So, your contractor should be installing an 80,000 BTU/HR gas furnace to deliver the same amount of heat that you were getting from the old one. The new furnace is also capable of delivering more air from the main circulating fan, causing increased resistance in your duct system. The new furnace will “short-cycle” because if it is over-sized. This will cause your new furnace to fail prematurely and cost more to operate. Repairs happen more frequently on over-sized system because they are turning on and off, instead of gradually heating your home and then shutting down. Tractor-trailer vs. Hybrid.
Your replacing your old 5 Ton – 8 SEER air conditioner with a new 13 SEER (minimum efficiency today) model. This is at least a 30% increase in efficiency over the old one. If you were to drive 100 miles in an SUV and then drive back in a fuel efficient car, would you need the same amount of fuel to get home? No; the heat will be removed more efficiently with a new unit and therefore wouldn’t need to be the same capacity to achieve the same result.
If you are replacing only equipment and not the entire system as a whole, you should insist that the company you choose to hire for your HVAC upgrades, does a proper load calculation on your home and determine the right sized system for your home and selects a system that will perform with the remaining components.