Three Myths About PTAC Units

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Packaged Terminal Air Conditioners (PTACs) offer a great energy-saving alternative to central air conditioning. Dormitories, hospitals, hotels, and apartment buildings often make good use of PTAC units  to provide guests with the most control over the individual space for the lowest cost. 

But you’ve probably heard some of the horror stories from building owners encountering PTAC-related issues that were detrimental to their business. For this reason, some people are hesitant about purchasing a PTAC unit, fearing that it might be a bad investment. 

However, many of the issues and concerns surrounding PTACs can be overcome with responsible maintenance and proper education about the model you choose. When selected and installed properly, PTAC units are a wonderful guest-focused solution for buildings with separate rooms or smaller, individual spaces. 

In an effort to debunk many of the assumptions surrounding PTAC units, let’s take a look at three common myths versus the truth behind each of them.

Myth # 1: Bigger PTAC Units are More Efficient

Many business owners believe that a larger PTAC will be more efficient for heating or cooling the space. This is not just a false statement -it can cause problems that can harm the building over time. 

When selecting a PTAC unit,  it’s most important to pick the correct size for your space. When talking about size, think about how it relates directly to power or output measured in BTUs (British Thermal Units). 

A BTU is the measurement of how much energy it takes for something to heat up one pound of water by one degree. With PTACs, the BTU rating describes how much power potential a unit has toward heating or cooling a space (by either adding or removing heat from the air). Typically, larger units have higher BTU ratings. 

In hotels and other guest-focused industries, PTACs are often oversized. This is because building owners tend to prioritize guest comfort over anything else, assuming that a larger unit with more BTUs will heat or cool the space much faster than a smaller one. 

The problem is that oversized units will technically reach the target temperature much faster than smaller units, causing them to stop running too early. This creates issues with adequate ventilation, overcooling, and condensation because the fan cannot run long enough to provide sufficient airflow to the space. 

For this reason, oversized units also turn on and off more frequently than properly sized units. This causes the PTAC to be inefficient in terms of power consumption and shortens the lifespan of the unit over time. 

Instead, the size of your PTAC should directly relate to the square footage of the space. As a general rule, you will need about 1,000 BTUs per 50 square feet of space. So for rooms that are 150-200 square feet, you will need a PTAC rated between 7,500 – 10,000 BTUs. 

That said, each space is unique. Different factors will affect how many BTUs are required to adequately control air quality during average conditions. Factors like sunlight exposure, floor level, number of occupants, and whether or not the unit is in a kitchen are all good reasons to select a unit with more or less BTUs. Although it should be noted that differences based on these factors usually only change the BTU requirement by 10-15%. 

Myth # 2: PTACs Help Reduce Mold

While it may seem possible due to its ability to consistently bring in outside air, the reality is that PTACs do not play a significant role in reducing mold. This is because they do not help with dehumidification. 

You may have heard stories where hotel owners experienced mold issues related to  a PTAC unit. This is often due to oversizing, poor maintenance, poor installation, and expecting more from the unit than what it can deliver. 

Oversizing contributes to mold because of an issue with latent capacity. The latent capacity is the unit’s ability to pull moisture out of the air (usually with heat) without heating up the temperature of the air. On the other hand, the sensible capacity is the unit’s ability to change the temperature of the air itself.

Oversized PTACs often do not run long enough to pull moisture out of the air. While the sensible capacity of a larger unit will technically change the temperature, the latent capacity decreases because the unit stops running too quickly. In many cases, an oversized unit that stops running like this will leave moisture and humidity in the air that would have been removed had the unit been able to run longer. Not only does this humidity still make the room feel hotter than it is, it also leaves behind unwanted moisture.

The fact is that PTACs are not dehumidifiers. While they are a cost-effective way to allow guests to control the temperature in a room among other benefits, they do not play enough of a role in dehumidification to avoid additional precautions. 

So how can you still use a PTAC and manage your humidity levels? First, make sure you select the right size PTAC for your space. Then take measures to pressurize, ventilate, and dehumidify the space in other ways to prevent mold buildup and maintain good air quality overall

No matter the space, steps should be taken to make sure each room is adequately pressurized. In some cases, reducing toilet exhaust can help with this, although you will still need to maintain legal levels. It may even be necessary to remove vinyl wall coverings and purchase a dehumidifier, depending on the needs of the building. 

Myth # 3: PTACs Will Work with Any Electrical System

PTACs are often used in apartment buildings and duplexes to provide individual HVAC control to tenants. You may also consider purchasing one for your own apartment. 

While these are a good investment, you will still need to pay careful attention to the amperage per unit in order for your PTAC to function properly. Some PTACs installed in residential spaces may turn on, but they may not be working at full capacity if the existing electrical system doesn’t support it. 

The key is to balance power (BTUs) with the amperage of your system to adequately manage the space without overloading your circuits. 

To be sure you are installing the right unit, consider the amperage of your existing electrical system and the amperage of the unit. PTACs come in three standard amperage ratings: 15, 20, and 30. Whatever the amps of your PTAC, you need to match this up to the amps of the circuit you will be running it on. 

For example, a 30 amp circuit should be able to handle a 30 amp PTAC. However, a 30 amp PTAC should never be installed on a 15 or 20 amp circuit. The opposite is somewhat more manageable (a 15 amp PTAC on a 30 amp circuit), but it is still a good idea to change the cord/wire size or the circuit breaker.

Final Thoughts

There are a number of different factors to consider when determining the right air conditioning solution for your home or business. PTACs are a good investment for cost, efficiency, and guest control settings. However, they are not a one-size-fits-all product. In order to make the smartest choice for your space, it’s important to know the truth about its abilities and how to select the best option. 

If you believe that a PTAC is the right solution for you, we have guides available that can help you select the right size, power rating, and wire gauge for your needs. With a wide range of new and refurbished models available, there are plenty of options to consider. Browse our catalog to find your best fit.