# Size Matters

One of the most common questions asked when installing a new air conditioner is, ‘what sized air conditioner or heating do I need?’ When you ask this question to a HVAC professional, you will usually get an answer with terms such as weather, load factor, home size, etc. Read on to gain an understanding of what these terms mean, how an HVAC size matters, and how they apply to your home.

## Calculating Size

Calculating the right size equipment for your air conditioner is not easy. There are a number of factors involved including room size, ceiling height, number of windows, thickness of your walls, insulation, etc. These are the house factors. Another important factor to consider is the environment you live in. Each part of US is broken by the National Oceanic & Atmospheric Administration into zones that require what is called Cooling Degree Days, and Heating Degree Days. Degree–days are climate metrics that can be used to project the energy demand required for space heating as outdoor temperatures change from reference temperatures. The reference temperature used is 65 degrees F or 18 degrees C.

Each of these zones needs different sizes of air conditioning or heating. On a broad scale, these can be slotted into a table that shows the square foot range by climate zone.

This table is meant to give you a quick and broad idea of the size that is needed for your heating or cooling depending upon where you live in the US. For example, an home in NY will need a completely different size as compared to a home of the same size in San Jose, CA.

## Why Size Matters

HVAC is not an one size fits all business. The multiple factors we discussed before have a direct bearing on the performance of heating and cooling systems. So what happens if I have larger or smaller unit? Let’s consider a car. Take a car that is meant to carry 5 people and 100 pounds of baggage. What happens when you stuff ten people in the car and load it with 500 pounds of baggage? First, every person travelling will be uncomfortable and, two, the engine will be strained beyond it’s capacity.

### A Larger Unit

An air conditioning or heating system that is too large for your house will be inefficient and an overkill. It is like using a bus to transport just 3 or 4 people. Some disadvantages of an unit that is too large are:

• Will consume more energy than needed. Large AC units or heating units need more energy to run.
• Will waste energy through ‘short-cycling’. Since the ac unit or heating units is large, it will cool or heat a room faster by brute force. As the heat or cold dissipates, the unit will have to come back on and start the next cycle of cooling or heating.
• Larger units create wider temperature swings, and will keep you uncomfortable.
• Larger units may force more air than needed through the ducts, and could create noise.
• The short cycles will also have more wear and tear on the unit, needing more repairs and maintenance.

### A Smaller Unit

A unit that is too small is like the overcrowded car with too many people and baggage. Some disadvantages of an HVAC unit that is too small for your home are:

• The heat pump and air flow fans will be stressed as they are forced to work continuously.
• Will fail to keep you comfortable in extreme weather conditions, and the needed heating and cooling will be beyond the capability of the unit.
• The continuous working will mean the unit will break down frequently requiring repair and maintenance.
• Will certainly mean more utility costs as the system is forced to work continuously.

### Right Sized Unit

A right sizeed HVAC system is ideal in terms of performance, efficiency, energy consumption and your comfort level with the following advantages:

1. Will operate efficiently and in the correct heating or cooling cycle.
2. Will maintain a more consistent temperature as well as indoor air comfort including humidity.
3. Will not generate excessive noise.

## What Factors Determine The Size:

As we said earlier, there are a number of factors that determine size. Let’s review the most important factors:

• The weather in the area you live in.
• The size of your home, its orientation, ceiling height, number of rooms, number of windows, etc.
• The material used for the construction of your home.
• Insulation and other weathering factors.
• Lights and other heat generating devices in your home.

## Who Does the Calculations and How?

The methods used for calculating the size is straight forward. At the same time, based on the high energy efficiency of modern heating and AC units, these calculations have become quite complicated. Professional HVAC consultants, such as the Peirce energy experts found right here, are trained to do these calculations day in and day out. Many of our contractors use a computer based program that has been designed and matured by the Air Conditioning Contractors of America (ACCA). The program is called the Manual J Residential Load Calculations.

## Let the Pros Size and Install Your System

If you live in Pennsylvania, call your nearest Peirce Phelps dealer. Each dealer on this site has been thoroughly trained to determine the best unit for home owners, and is an authorized dealer of Carrier heating and cooling systems, manufacturers of the new Variable Speed air conditioning and heat pump units. The Carrier Variable Speed (VS) units are smaller, quieter and more efficient. These units are available in sizes that will be ideal for you home. Use the services of our dealers to identify and install a right heating or air conditioning system for your home.