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Pressurization and How to Optimize Your Restaurant

Jul 10, 2017 2:28:54 PM

Pressurization issues in your restaurant

Building pressure affects guest comfort, utility costs and equipment life. You likely have a pressurization problem in your restaurant if:

  1. You have experienced unwanted odors or smoke creeping from your kitchen into the dining area
  2. Your guests have found the doors to your restaurant difficult to open
  3. Doors don't seem to close all the way on their own
  4. Maintaining room temperatures in your building is difficult

While these may seem like minor issues, the costs of discomfort, energy loss and shorter equipment life add up.

What Are the Real Costs of Pressure Imbalance in Your Restaurant?

The largest cost you are likely to incur is that of fewer customers due to the unfavorable indoor environment quality (IEQ) created by the pressure imbalance. Restaurant patrons are more likely to return and tell their friends and family of the nice atmosphere when your IEQ is high.

Other costs that can be immediately quantified include:

  1. Utility costs, of which you may be  paying 10% more due to the pressure imbalance
  2. HVAC equipment life, which could be reduced by up to 33% if your system is working to compensate for a pressure problem 24/7
  3. Maintenance costs of an inefficient system

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Typical Reasons for Pressurization Problems

A pressurization problem will eventually cause leaking through building insulation that could become permanent. Small differences in cubic feet per minute (CFM) can lead to big pressure differences, even in well-insulated modern buildings. 

Typical reasons for negative building pressure:

  • Dirty filters (some negative pressure)
  • Outside air damper stuck closed (medium negative pressure)
  • Makeup air (MUA) unit turned off or inoperable (extreme negative pressure)

Typical reasons for positive building pressure:

  • Outside air damper stuck open or not optimized to balance pressure (medium positive pressure)
  • MUA taking in too much outside air (extreme positive pressure)

Ideally, your restaurant will have a slight positive pressure (a water column reading of .01" to .02")

How to Optimize Pressure in Your Restaurant

First, you should ensure you have fully functioning economizers on all of your rooftop units (RTUs). Economizers use sensors to measure air enthalpy (the sum of internal energy and the product of pressure and volume), humidity, CO2 and temperature to optimize for the "free cooling" available from taking in outside air when enthalpy and air quality are at acceptable levels. Considering the equation for air enthalpy, you can see that even a small pressure imbalance can affect the enthalpy, and thus the comfort level, of your entire restaurant.

Second, a differential pressure sensor in your restaurant would measure relative pressure of the interior versus the exterior of your building. Even though your RTUs may be constant air volume (CAV) units, the outside air dampers can still be modulated with rooftop economizers to only allow in the exact amount of outside air required to balance the interior pressure.

In the process, a demand-control ventilation (DCV) system can measure CO2 levels, balancing fresh outdoor air intake while keeping your dining area slightly more positive pressure than your kitchen, which ensures unwanted odors and smoke do not adversely affect the experience of your guests.

Restaurant differential pressurization sensor

You can’t afford to let insidious damage and costs caused by pressure imbalance to continue. Your choices are either to add procedures to regularly measure airflow, or to find a building automation system that can proactively automate detection and correction measures for you.



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