How to Size up HVAC Systems

How to Size up HVAC System

HVAC means the heating, ventilation and air-conditioning system which is the common essential technology that keeps you healthy and comfortable in your home or office. This technology controls your indoor temperature and it is important to size up HVAC systems properly. The HVAC system is variable in terms of size and can be designed to fit the area or space of your room. The size of an HVAC affects its efficiency in heating, ventilating and cooling the room. It also affects its operating cost and increases your monthly energy bill. Therefore, it is important to determine the area of your room and have the appropriate size for your HVAC system.

Specialists use precise methods for sizing an HVAC system, however, the simple “rule of thumb” method is generally used by estimators to roughly size up an HVAC system for a room.

The Rule of the Thumb Method

1. Firstly determine the square footage or area of the room that needs an HVAC system. You can refer to the blueprints for its exact measurements or just measure the room using a calibrated tape measure.

2. From your measurements, get the product to have you’re square footage of the area by multiplying the length and width of the room.  Multiple the square footage by one to get your CFM. Then divide the CFM by 400. This will give you an approximate or ballpark estimate of the number of cooling tons you need for the room. HVAC systems are already designed according to tonnage and have equivalent square footage of rooms to fit in.

3. HVAC specialists also considers factor in specifics such as the appliances that generate heat, amount of insulation in the room, roofing, windows and the climate.

4. You can however fine-tune your estimate considering the factors in number 3. Instead of 400, you can divide the property’s CFM by anywhere from 300 to 500, considering the additional factors. This will also depend on your personal temperature preference.

The Centralized HVAC System

Typically, the latest HVAC systems are designed with a central unit that provides the heating, ventilating and cooling load for a section or a room of a building. It is critical to calculate properly the HVAC size appropriate for a space to ensure the ideal heating, ventilating and cooling while you keep energy costs down.
An undersized HVAC unit too small to heat or cool a room will constantly run and never fully cool the interior or the room. While an HVAC unit that is too large for the room is bound to short-cycle, a symptom of either obstructed thermostat, leaking refrigerant or iced coils and therefore can use excessive energy as well. Here is how to determine the size of a Centralized unit for a section or a room in a building.

The Procedure

1. Begin by measuring the total square footage of the room you plan to regulate with an HVAC unit. Calculate the product of your square footage by multiplying the length times the width of the room.

In planning to regulate multiple rooms in a building, you must measure the dimensions for each room before adding the totals together. The building’s blueprints often stipulate the total square footage of the space, however, it is best to double check those numbers and measure them again.

2. Then determine the CFM or Cubic Feet per Meter figure for your entire environment.

The airflow is measured in CFM. The general rule of thumb of HVAC systems for most states in the United States dictates the standard one CFM per one square foot rule. However, there are also exceptions to this rule considering other factors. For rooms with several windows, HVAC system estimate may use a two CFM per square foot standard.

3. Next, is to divide the total CFM figure by 400 and convert it into tons.

To demonstrate the procedure;

If the total square footage is 1,200, multiply it by 1 and you get a 1,200 CFM. Then divide 1,200 CFM by 400 and you will find that you need a three-ton air-conditioning unit for your HVAC system.

Having several windows in your room can change the formula. Multiply 1,200 square foot by 2 and you get a 2,400 CFM. Divide 2,400 by 400 and you need a 6-ton HVAC system for a room with several windows.

There are parts of the country with extremely hot summers. Size up your air-conditioning system using a one-ton per 300 CFM ratio. In this case, simply divide your CFM figure by 300 instead of 400 to determine the proper tonnage for the room.

Always remember, if you improperly size up an HVAC unit, it will always lead to earlier equipment failure aside from higher energy costs in your monthly bill. An air-conditioner that is too small is just as inefficient as one that is too big for the space. Size up HVAC systems properly.