EOS: The Perfect Solution for Perimeter Overhead Heating & Cooling

All engineers want to design the perfect system. But, as most young consulting engineers soon find-out, HVAC design is a game of compromises. Their goals are occupant comfort, energy savings, system controllability, and installed cost.

The air-conditioning of perimeter zones in commercial buildings is a perfect example of these compromises. Almost all buildings require heating and cooling at the perimeter during different times of the year. Most commercial buildings in the U.S. are overhead mixed systems. Overhead systems work well in cooling with proper diffuser selection. Overhead heating is a different story.

A good solution would be to provide overhead cooling and baseboard heating, but providing two systems is cost prohibitive. Here, the engineer is faced with his/her first compromise. A fairly common compromise is to provide a perimeter slot diffuser with either a dedicated down-blow section -- to provide some heat to the floor -- or a diffuser with split pattern control so half of the air can always be directed down while the other half is directed horizontally across the ceiling.

As a compromise, this method works, but it is not the optimum solution. In both heating and cooling modes, half the supply air is being discharged in the wrong direction for optimal comfort and energy savings. In heating, half of the supply air is discharged horizontally causing stratification along the ceiling. In cooling, half of the supply air is discharged vertically causing unwanted drafts along the floor.

The award-winning Titus EOS is a solar-powered, energy-harvesting plenum slot diffuser designed to provide the perfect perimeter solution for those imperfect perimeter compromises. The EOS automatically changes the air-discharge pattern to horizontal for cooling or vertical for heating. 

When 100 percent of the supply air is effectively utilized, the room temperature reaches set-point faster. This allows the HVAC system to run for a shorter duration of time and save energy. Lab tests show the savings to be as high as 30 percent, which makes it a great choice when designing buildings for LEED certification.

The EOS increases occupant comfort and saves energy without the use of any external power source. The auto-changeover ac­tion is powered by a unique energy harvesting system which uses solar or ambient light energy to power a miniature motor/accua­tor assembly. A PC board with temperature sensor uses smart logic to monitor supply air temperature and quickly change the air-discharge pattern.

With the EOS, Titus continues as the industry leader in innovative design by providing an energy efficient and cost effective solution for the perimeter heating/cooling dilemma.

Please direct questions toward Titus Communications (communications@titus-hvac.com) and/or Titus' GRD Product Manager Mark Costello (mcostello@titus-hvac.com).

What are the Minimum Minimums for Digital Typical Controllers?

Minimum minimums are the minimum airflow limits Titus recommends for accurate airflow control on terminal unit inlets. Many customers have noticed that Titus’ 2014-15 Product Catalog contains updates regarding these values. In this entry, we will reference the “DESV - Digital Typical Controller” section found on pg. M14.

The original minimums that we established many years ago were based on factory-calibrated pneumatic controls. It was determined that factory-calibrated controls could maintain an accuracy of +5% if we did not try to set the minimum airflow limit too low. Of course, you can always order a unit set for full close-off because that is not really airflow control.

For the Titus II and IIA, we determined that a minimum airflow based on a sensor signal of 0.03 in wg could be controlled within +5%. The Titus I required a slightly higher sensor signal of 0.05 in wg in order to deliver the same accuracy. Later, analog and digital electronic controls were assumed to be equivalent to the Titus II and IIA controls with regard to the minimum control accuracy.

Here are the minimums for Titus I:

• Size 04 = 55 cfm
• Size 05 = 85 cfm
• Size 06 = 105 cfm
• Size 07 = 135 cfm
• Size 08 = 190 cfm
• Size 09 = 225 cfm
• Size 10 = 300 cfm
• Size 12 = 425 cfm
• Size 14 = 575 cfm
• Size 16 = 750 cfm
• Size 40 = 1800 cfm

Here are the previous minimums for Titus II, Titus IIA, TA1/TA2 and digital controls:

• Size 04 = 45 cfm
• Size 05 = 65 cfm
• Size 06 = 80 cfm
• Size 07 = 105 cfm
• Size 08 = 145 cfm
• Size 09 = 175 cfm
• Size 10 = 230 cfm
• Size 12 = 325 cfm
• Size 14 = 450 cfm
• Size 16 = 580 cfm
• Size 40 = 1400 cfm

During the preparation of our latest catalog, it was decided these minimum values should be reduced in recognition of the improvements that have occurred in digital electronic controls (specifically, their electronic flow sensors).

We reduced the minimums based on a sensor signal of 0.01 in wg. As always, the actual flow-control accuracy depends on the quality of the controller, but our lab testing has shown that some controllers can provide +5% accuracy down to a sensor signal of 0.005 in wg.

Here are the latest minimums for digital controls:

• Size 04 = 30 cfm
• Size 05 = 40 cfm
• Size 06 = 45 cfm
• Size 07 = 70 cfm
• Size 08 = 90 cfm
• Size 09 = 120 cfm
• Size 10 = 145 cfm
• Size 12 = 190 cfm
• Size 14 = 300 cfm
• Size 16 = 385 cfm
• Size 40 = 720 cfm

Titus’ minimum minimums for digital controls are much lower than they have ever been. This should be a welcome change for designers whom want accurate airflow control without increasing the minimum airflow volume to achieve it. We have redefined how low you can go!

Please direct questions toward Titus Communications (communications@titus-hvac.com) and/or Titus' Chief Engineer Randy Zimmerman (rzimmerman@titus-hvac.com).