PolarPlex Drop-Away Roof Panels are a Clear Winner

cac_1_blogthumbcac_1Our popular PolarPlex Drop-Away roof panels are designed for use under existing data center fire suppression systems that activate at 165 degrees F so they don’t require complicated and expensive changes to your existing fire suppression regime. The PolarPlex Drop-Away panel inserts are also thermally activated, falling out of their frames at 135 degrees F, so in the event of a data center fire, your existing fire suppression system works unimpeded.

Another important containment design consideration is ensuring adequate lighting in the cold aisle. With the introduction of a clear PolarPlex Drop-Away Panel, Polargy addresses this customer requirement in a simple way.


Our new clear Drop-Away Panels allow 90% of light into the aisle while our Frosted Drop-Away Panels allow 80% of existing light in, which means they don’t require complicated and expensive changes to your data center lighting system.

We will be showing both our Clear and Frosted Drop-Away roof panels at the Data Center World Global Conference 2014 in Las Vegas this week. Stop by the ASM Modular booth# 619 to see a full suite of our PolarPlex containment solutions and even some of our more popular airflow accessories, such as PolarDam Air Dam Foam and PolarFlex 42U Full Rack Blanking Panels.

Space is Limited in Manhattan

I visited a banking customer in Manhattan last month and finally had the opportunity to revisit an installation Polargy had completed several years back. The bank had discovered too many hot spots in their data center and looked to Polargy for a solution. Their problems were caused by the room’s space limitations of a short ceiling and a cable cluttered  12” raised floor. As densities grew, so did their hot spots.

Al Helmke of JEM Tech in the Bank

Al Helmke of JEM Tech in the Bank

After assessing the available space and airflow patterns, Polargy installed PolarPlex TM Drop-Away Panels for cold aisle containment and a strip curtain door to close off the end of the aisle. The project was a success in that it solved the bank’s hot spot problems: intake air temperature dropped from 90°F to 70°F.

Al Hemlke, of JEM Tech, is pictured above in the cold aisle of the data center. Al is a well-known, respected industry veteran who is deeply familiar with the NY/NJ market and leads our relationship with this customer. The PolarPlex Drop-Away Panels are situated just above him and the strip curtain door can be seen at the far end of the aisle behind him. Generally, we avoid strip curtains because the curtains can sometimes dance due to airflow characteristics at the end of aisles. However in this case, the airflow was not strong enough to create a problem.

Because of space limitations in Manhattan, many data centers have relocated outside the city proper, to surrounding communities in New Jersey, other New York neighborhoods, or into Connecticut. Confined spaces can lead to the types of density problems our banking customer experienced. However, as they discovered and I was able to see in action, sometimes all it takes to solve the problem is a reevaluation of containment and airflow solutions. High density issues can still be addressed even while working in a limited amount of space.

Bernoulli Makes Curtains Dance

One problem we have seen with curtains on cold aisles is the flapping or drawing in of the curtains due to the airflow through the adjacent perforated tiles. Sometimes people call this the “dancing curtain problem.” The Bernoulli effect (air plane wing effect) of lower pressure on the side of the higher air velocity causes this. This flapping can push the curtains close to the server intakes and then the suction of the intakes can suck the curtains onto them, blocking and essentially starving the servers. We caught this blocking three times before we adopted a policy of avoiding curtains on cold aisles.

After examining this and having the good fortune of a customer doing some testing we concluded that flapping curtains are not a fuction of air balance in the contained zone. Rather, it is a function of turbulence caused by the airflow through the nearby tiles. So, even if one has an oversupply of air, the curtains just don’t push out gently as one might expect.

We tried adding weights to the curtains to prevent their movement, but this only resulted in heavy flying objects banging into the servers. Ultimately, we added two solid panels to the sides of the strip door. By the time we did this, the cost was about the same as a sliding door like the one pictured below.

Sliding Door Preferred Over Curtains for CAC

The design approaches to combat the flapping curtains include:

  • Hot aisle containment – there is no air flow from the floor
  • Sliding doors – they don’t move
  • Solid floor tiles at ends of rows – no nearby air movement
  • Extended containment perimeter – basically place doors away from aisle end in some manner

Containment Needs Control

Today I talked to a facilities engineer for a lab data center. They have already added strip curtain doors to the ends of the cold aisles and the top of the aisle remains uncapped. Next, they plan to install VFDs and put temperature sensors at the rack tops in the cold aisle. They plan to drive the VFD’s off the temperature at the top of the cold aisle.

This is an interesting approach because it seems to assure that the air flow is sufficient to the cold zone. And, with an open top, it is especially important to assure sufficient cold air into the aisle. Without that, or in an under-supply situation, the aisle would take hot exhaust air from over the tops of the racks.