February 2010

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Retrofit Strategies

What can I do to make my building more efficient?
 

Steven R. Calabrese
Steven R. Calabrese
Control Engineering Corp.

Contributing Editor

 

In the wake of the recent/current recession, my focus has been not so much on new construction, but on retrofit work. It seems as though many building owners and facilities managers have been reluctant to invest in expansions and additions, and are looking for alternative ways to best utilize the space that they have. Part of this process is to find ways to “cut back” on energy usage and optimize building systems to that end. Easier said than done, but given the right direction, a facility can meet that end, and it is up to us in the consulting and contracting world to help our customers achieve these goals.

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In our firm we’ve begun an in-house initiative designed to help find opportunities for energy savings, and to facilitate the implementation of any energy-saving measures. Our position is that all buildings waste energy, at least to some extent, and thus wasted utility cost is always some percentage of the whole. Our program is designed to go out and survey a facility’s systems and energy usage, and recommend ways to minimize waste. In doing so, we typically identify problems and recommend solutions in the form of systems upgrades and retrofits. Following are just a few of the different strategies that we endeavor to propose and implement.

Variable Frequency Drives

In HVAC, the types of motors that we typically deal with are those that drive pumps and fans. Some of these pumps and fans are equipped with variable frequency drives (VFDs), by the nature of their design intents. A VFD provides for the means of varying the speed of an electric motor, by varying the AC frequency (power) delivered to the motor. For variable fan and pumping applications, VFDs are a requirement. For other types of systems that are conventionally served by constant volume fans and pumps, there are opportunities to equip the motors of these fans and pumps with VFDs, and thus vary the energy usage of these motors, if not automatically, then at least as a manual procedure.

Implementation is straightforward. Replace the motor’s three-phase starter with a VFD of appropriate size. Control the VFD via an external signal that varies as a function of some monitored value. Or simply dial down the motor speed manually at the VFDs user interface, when conditions allow. Any time the motor is operating at less than full speed, energy savings are incurred.

Lighting Upgrades & Control

Lighting upgrades are a big deal these days. To change out incandescent fixtures for fluorescents is a major step in avoiding excessive energy usage. You probably know that this is true, as if you’re anything like me, you’re currently going through your own household and replacing incandescent bulbs with those new-fangled “twisty” fluorescent bulbs. In facilities that already have fluorescent lighting, the upgrade path to more efficient fluorescents exists, if the existing fluorescent bulbs and fixtures are of the older “T12” variety, which by visual inspection are thicker than the newer “T8” bulbs. The upgrade requires a “swap-out” of the existing fixtures with new fixtures, or a conversion of the existing fixtures to make them compatible with the new bulbs.

Lighting control is something that can be implemented in a number of ways. Occupancy sensors can be installed, to activate interior lighting when people enter the particular areas served. General lighting can be scheduled via the Building Automation System (BAS). Exterior lighting can be controlled by using a daylight sensor to determine when to operate outdoor signage, parking lot lighting, and building grounds lighting.

Implementation of lighting control requires that the lighting system be somewhat automated. The lighting may be operated by some supervisory lighting system marketed by a lighting manufacturer. If no such system is in place, any lighting that’s desired to be controlled in any of the above fashions would do well to get on the facility’s BAS. Individual lighting circuits can be controlled by digital outputs. These outputs can be scheduled through the BAS, or controlled as a response to daylight or occupancy sensors that are wired as digital inputs to the BAS.

Start/stop of Miscellaneous Equipment

Sounds simple, right? Well, it is! Your BAS currently controls many pieces of equipment in this fashion, not the least of which are fans and pumps. Anything related to HVAC and requiring two-position control (ON/OFF, OPEN/CLOSED, ENABLE/DISABLE) is likely controlled via the BAS by a digital (two-state) output. But what about that other stuff in your facility? That stuff that seems to just run all the time, even when it’s not required to be in operation? You eventually go over and turn it off, only to turn it back on again when you need it to operate. Can’t you get that process automated? What benefits would that afford if you were to do that with, say, your outdoor sprinkler system?

Reliable Controls Well, in sticking with the afore-mentioned example, your sprinkler system is likely already automated, in that it will come on at predetermined intervals to water the grass on your building grounds. I use this example because years ago I worked for a company whose sprinkler system would turn on in the middle of a rainstorm, and the owner of the company would be cussing up and down the halls about it! Pretty funny when I look back on it, but the example does serve a point, and that is, why not have these types systems and equipment that are not conventionally under control of the facility’s BAS, on the BAS for the purpose of enable/disable? For the sprinkler system, you can install a precipitation sensor outdoors, and disable the system if it’s raining. Or better yet, utilize Internet-based weather information and disable the system if there’s rain in the forecast.

Other systems that come to mind that would be good candidates for enable/disable via the BAS are, well…really anything that can be put to a schedule. How about outdoor fountains? TV monitors in rec rooms and fitness centers? Coffee makers and water coolers? And the list goes on.

Metering

Definition (for our purposes): to monitor processes or energy consumption with an electronic meter that can convert the measured variable to an electronic signal that can be tracked via the BAS. Typical applications include monitoring of natural gas, electricity, water, airflow, BTU consumption.

Two idioms to consider here: 1) you cannot control what you can’t measure, and 2) if you’re monitoring, you can try things. Basically the first implies that you cannot control say, energy consumption, if you cannot monitor it, and the second implies that you can do that by trying different things and seeing what works without compromising occupant comfort and system acceptability.

Install meters at system points to monitor whatever process or utility desired. Monitor the meter signal via the BAS and implement strategies that utilize the signal to save energy, optimize system operation, etc. More about metering in a future column (so be sure to stay in touch!).

Wireless

I include this topic because its applications are well-suited to existing buildings, especially older buildings that have thick concrete walls and plaster ceilings. The current state-of-the-art in wireless transmission and reception is far superior to what it was just a few short years ago, and costs have come down with reliability going up.

Applications range from parking garage CO detection and ventilation systems, tenant redesigns, facility repurposing, basically any project where it would be difficult to install new cable and conduit. Install the wireless components (transceiver and sensors), and interface the wireless system to the BAS, via hardwire connections or via communication protocol. The topic of wireless is worthy of its own column, so rather than include too much on it here, I defer to a future column on wireless technology, applications, guidelines, and pros and cons. For now well just say that it’s certainly a technology whose time has come, and we’ll be sure to see more and more products dedicated to the concept.

Tip of the Month: There are many good resources on the Web pertaining to energy usage and building efficiencies. You can find useful information at the following sites:

• Building Owners & Managers Association (BOMA) International, www.boma.org
• U.S. Dept. of Energy, www.energy.gov
• U.S Energy Information Administration (EIA), www.eia.doe.gov
• Energystar, www.energystar.gov
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