Properly sized equipment improves comfort and reduces costs, maintenance, and energy use.
Determining the correct size of heating and cooling equipment is the key to achieving home comfort (temperature and humidity) and saving on initial and ongoing operating costs. Equipment can be either oversized or undersized, but most prevalent mistake is oversizing equipment. And believe it or not, oversizing is a bigger problem than undersizing. It’s a BIG mistake that you want to avoid! When equipment is oversized:
- Initial costs are higher.
- Efficiency is reduced.
- Energy costs increase.
- Your comfort is compromised.
- You’ll most likely experience more service calls and more service issues.
- The longevity of your new equipment will be compromised.
Properly sized equipment is especially important in humid climates, where short-cycling of air conditioning equipment can lead to poor humidity control. A similar parallel would be an automobile in stop-and-go traffic – the overall efficiency of an air conditioner, furnace, or heat pump is reduced by excessive cycling. More starts and stops accelerate wear and tear on the equipment, which can lead to premature failure.
Oversized systems also use more fan power for the blower and often exhibit more duct leakage due to higher operating duct pressures. Finally, oversized air conditioners and heat pumps greatly aggravate the peak demand on extremely hot or cold days.
To make sure you don’t fall into the” bigger is better” trap. Follow these simple guidelines:
Beware of causal sizing estimates – this is when a contractor uses your square footage or contractor “experience” as the basis for product recommendation. Do not settle for this as it will cost you more in the long run. A good contractor will run a heat loss/ gain report. The industry provides a guideline found in Manual J and Manual S (produced by the Air condition Contractor’s Association of America or ACCA).
**Unfortunately, ACCA approved sizing methods are often not used and over-sizing is very common. According to one survey, nearly 40% of contractors indicated that they purposefully over-sized equipment, citing reasons such as “to reduce call backs, “ to allow for future expansion,” or “customer demanded it.”
Industry guidelines state that the heating and cooling loads are based on the amount of wall, ceiling, window, and floor area, their insulation value and the building envelope and duct air leakage. Other factors are building orientation, roof surface color, and occupancy. Insist that your contractor due their due diligence in selecting properly sized equipment for your new heating and cooling system.
Don’t forget the ducts. Air leakage and heat losses from ducts rob your furnace, heat pump or air conditioner of its capacity under peak conditions. So you’ll want to make sure that duct sealing and testing are part o your plan for sizing and installing a new air conditioning or heating system.
Select a programmable thermostat. Your system is not complete without selecting a programmable thermostat. This will improve sizing-related performance and potentially save energy associated with more reliable thermostat set-back and set-ups.
The above requirements are normal practice for a professional heating contractor. There is a great value in dealing with an experienced HVAC contractor. Call on a YORK heating and cooling contractor to get a proper assessment of your home’s needs and making sure you get properly sized equipment for your heating and cooling system.
York Heating and Cooling