Category Archives: Capacity Maximization

The myth of the 15-ton compressor

For those of you that don’t know I started in the industry¬†as a facilities technician, then within three months became a site lead mechanical engineer. One thing that always perplexed me was the persistence of the 15-ton (or any nominal sized refrigeration component) compressor. Even today, working as a regional engineer over 3000 miles of data center footprint, I still deal with this from people who should know better.

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Immersion cooling: That’s how I learned Portuguese that one summer, right? (updated)

No, not quite. Immersion cooling has been around for a long time. Most commonly, you might recognize the large fins on utility power transformers. They are cooled by immersion, with the heat radiated by those fins. Its only recently, perhaps the past 15 years, that the concept has been applied to personal computer cooling mainly by hobbyists trying to do something different and cool, but ultimately likely being a little disappointed as other more mainstream technologies gave them their “bleeding edge” computing performance. Even more recently, this concept has started to be applied to data centers. Continue reading Immersion cooling: That’s how I learned Portuguese that one summer, right? (updated)

Is airline travel too safe?

I just read an interesting article providing a nice contrarian perspective on airline¬†travel domestic and abroad. It compares the cost of a life saved relative to money spent in other areas. Keep in mind, I’m writing this at the airport so I am painfully considering the implications of the points I am making. While this may seem ludicrous at first, the idea of making something less safe, I realized that this might help me make an interesting point effectively, one that I struggle to articulate. The article points out how more effective spending on vaccines, safety belts in cars, and other areas of our lives relate to the money spent on aviation safety. Because of very effective FAA regulations, poor countries spend a lot of money on aviation safety while school children are unvaccinated and traffic deaths occur at significantly higher rates.

So what point, relating to data centers, could I be getting at? Are we spending money in the most effective manner to realize high availability. Much like the net loss of life in poor countries would be lower if they allocated resources where they have the most impact, so too we can improve our loss of compute by investing where impacts are highest.

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Chill water resets

Do you have a chiller plant? Is your air handling equipment operating at some level below 100%? You can probably benefit greatly from a chill water reset, especially if you operate with a largely sensible load (like a data center!). Even if you have latent cooling, the latent capacity is not impacted as much as you think by higher chill water temperatures. The coils leaving air temperature is what determines how well the air handler removes humidity as that air is typically at saturation. So as long as you are meeting your air temperatures set point, latent capacity is not impacted.

So what of the chill water reset? Well, ASHRAE recommends, in a series of articles co- authored with Taylor Engineering, the use of a chill water temperature reset followed by a chill water d/p reset.
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Maximizing Utilization by Revisiting SLAs

First, let me define SLA as it relates to this discussion. SLA is service level agreement and for the facility minded individual is how we guarantee conditions at the server. We guarantee uptime and with properly corded devices we guarantee customers will not lose power. We also have temperature and humidity SLAs. They might be do not exceed 60-89 degrees f and 20-80% relative humidity for more than 4 hrs, for example. Now we have a target band tighter than that but that is our promise.

With that understood, we can start the discussion. Let’s say we have 2 MW busses with 4 primary and 1 redundant bus using static transfer switches to transfer to the reserve (redundant) bus. Let’s say that each bus has 1400 kW of UPS power, requires 100 kW for house loads, 100 kW for UPS losses, 40 KW for lighting, and 760 kW reserved for design day cooling. As we can see we will not be able to use about 400 kW of installed UPS capacity. Continue reading Maximizing Utilization by Revisiting SLAs