Greg Nickels vows to DOUBLE Seattle Conservation Programs

A recent article in the Seattle times indicates that the City of Seattle is getting serious about conservation:

Overlooking the Seahawks' field, Seattle City Light officials and Mayor Greg Nickels announced a $185 million plan Wednesday to double the city's energy conservation over five years -- an amount equal to the annual energy use of 180,000 Seattle homes.

The program, which targets residential and commercial electricity use, could save customers $310 million over that time.

"We are putting our conservation program on steroids," Nickels said.

The plan is available online at http://www.seattle.gov/light/conserve/docs/Conservation_5_Year_Action_Plan.pdf, and focuses on Lighting, HVAC, Industrial Processes and Data Centers.



Learn more about what this means to you and your business at http://www.seattle.gov/light/conserve/

Information on rebates, including spreadsheets to calculate rebates for common measures (VFD's, chillers, heat pumps, etc) is available at http://www.seattle.gov/light/Conserve/Business/cv4_ess.asp

Don't miss out on a great opportunity to fund your project and lower your operating costs at the same time!

Fan Engineering: Spark Resistance Ratings

Every once in a while we will see a specification for "explosion proof" fans. While this may be a desirable characteristic, "explosion proof" is not a specifiable option, and usually is included because of confusion with electrical component (i.e. motors, disconnects) specifications.



Instead, fans are generally classified by "spark resistance". AMCA has created a standard that defines three different levels of spark resistance, classes A, B and C.

These classes, listed in decreasing order of assurance, are generally concerned with the prevention of sparks caused by the rubbing together of spark-producing metallic components (generally ferrous materials). These classes only address spark risks due to an explosive airstream, and do not address explosive conditions outside the fan. A summary of the different levels of protection is found in this helpful engineering paper from Twin City Fans.

Type C: The fan is designed so that if the impeller or shaft comes loose and shifts during operation, two ferrous parts will not come into contact.

Type B: In general, this requires a nonferrous impeller and a nonferrous rubbing ring around the shaft hole. Also, extra locking systems are required to prevent the fan impeller, shaft, and bearings from shifting.

Type A: This requires a nonferrous airstream. Also, the extra locking systems are required as in Type B.

As with any engineering decision, the correct level of spark resistance to specify depends strongly upon the particulars of the project: The gasses or substances expected, the concentration of these contaminants, the location of the air-moving device, etc.

Smarter Starters

As anyone who has specified or supplied them on projects knows, motor starters can be a big headache. And despite the growth in the use of VFD's in today's energy conscious designs, motor starters still are used on about 60-70% of the motors provided in the industry. Typical problems can range from the very basic to the more involved. Some of the problems our customers report are:

• Incorrect overload protection provided or heaters incorrectly sized
• Incorrect control signal available on the site
• Not enough BAS points to provide needed damper or valve interlocks

For the most part, starters are old technology. Cerus Industrial re-examined starters and found that a lot of benefit can be gained from re-working these components to take advantage of today's technology.

Cerus BAS Starter

Protecting The Motor

Besides starting the motor, the main function of a motor starter is to provide a measure of protection to the motor in case of an electrical malfunction. Typically, this protection is provided by means of an overload protection in the starter that trips power in case the motor pulls more amps than it is safely rated for. Traditionally, this has been provided by means of small heater elements that are rated for the motor FLA. These are interchangeable and different motor operating conditions will require different heaters.

In practice, these heaters can be problematic--Essentially, they must be sized correctly for the operating amps of the motor, and this may or may not be known at the time they are purchased. Many things can change a motor duty point from the design to the installation: product substitution, air or water balancing, changes to the design, etc. And since these heaters have very small operating ranges, even a small change in any of these criteria can result in a heater change. In fact, replacing starter heaters are one of the most commonly reported change orders.


Adjustable thermal overloads have been developed to allow a greater amp range for a starter overload protection, but the biggest ranges available are provided via solid state overloads. Solid state overloads typically provide about a 5:1 amperage adjustment (from 1A to 5A, or 4.4A to 22A in two typical sizes). This essentially allows a single overload device to protect any motor that would reasonably be started by a given contactor, meaning that starters equipped with solid state overloads will always have the right overload protection for the motor they are starting. And solid state overloads add phase loss protection, giving your equipment even better security.

Cerus has standardized on solid state overloads for their HVAC starter line, to greatly simplify the process of selecting the correct starter and to avoid last-minute trips to the electrical supply house to get the right overload protection.


Communications

Almost all available starters use 120v relays to communicate with building controls. However, almost all available building operating systems use 24v power for their signals. This means that in order to provide a control signal to the starter from the BAS, interposing relays are required to convert the 24v signal to a 120v signal. These relays are usually field wired, and therefore add complexity and field labor costs to the installation of motor starters.

Cerus has greatly simplified the interface between the BAS and their starters.


All of their standard starters have a terminal strip that can accept a 120vac, 24vac or 24vdc signal directly. The terminal is self-calibrating, and will adjust to whatever signal is provided automatically, greatly simplifying field wiring. In addition, this terminal strip has a terminal that will accept a dry contact, if that is the preferred method of control.

But even greater communication flexibility is provided in Cerus' new line of BACnet enabled starters. Integrating BACnet allows direct communication with the BAS system via a single network connection. The BAS system can provide start/stop signals, interlocked damper control, receive proof of flow via current sensing, monitor the runtime and HOA position remotely, detect phase failure or phase loss, and enact fireman's overrides or emergency shutdowns. These starters provide unequaled ease of use and troubleshooting capabilities and require the absolute minimum in field labor to accomplish this.

BACnet points matrix


Simplified Interlocks

Many fan systems have control dampers that are intended to close when the fan is not operating. These dampers can serve to isolate a single fan in a multiple fan array, or may serve to prevent undesired airflow when the fan is not operating. However, these sorts of systems present a problem--The damper must be opened before the fan is turned on in order to prevent overpressurization of the ductwork. This is typically is handled by the BAS sending a signal to open the damper, having and endswitch on the damper send a signal back to the BAS to indicate that it is open, and then having the BAS send a signal to start the fan. This requires three control points on a BAS controller. Often, these control points are limited, and may or may not be available without a significant cost impact. Cerus has again simplified things by providing for a direct interlock between the fan motor and damper. In this system, the BAS sends a signal to start the fan, then the starter sends a signal to the damper and waits for a confirming end-switch signal before it will initiate the fan. This eliminates two control points from the BAS and greatly simplifies this critical interlock.



Additionally, the control terminal strip for the Cerus BAS starter has dedicated contacts for emergency shutdown and fireman's override.

And More to Come

Cerus is quickly adding functionality to their BAS starter line and upcoming features will include revenue-grade power metering and automatically calibrating motor overload protection.

Smarter starters use today's technology to reduce installation costs, minimize field problems and simplify troubleshooting.

Cerus BAS motor starter specification
Cerus BACnet motor starter specification

Seismic/Hurricane Certification for Air Handlers

When the IBC was adopted by Washington State, it brought in some new requirements in air handler construction and certification. These new rules required that for some projects, non-structural building components had to be shown to withstand, and in some cases operate after, a catastrophic seismic event. The intent of these rules was to provide critical facilities (first responders, hospitals, etc.) with systems that would likely survive an earthquake that would cause widespread damage elsewhere.

Likewise, Dade County Florida has created requirements for hurricane resistance for various building components, including rooftop Air Handlers. Rooftop Air Handlers must pass a rigorous series of tests to show compliance, including pressurizing a test section of the cabinet to over 30" of static and firing a 2x4 at the cabinet to simulate hurricane-blown debris!

Climate Craft has been a leader in the industry in showing compliance with both of these standards. They were one of the first manufacturers to show compliance with the Dade County requirements, as these videos from the testing attest:

Missile Testing

Cyclic Pressure Testing
Pressures up to 30" wg cause deformations of the cabinet well-beyond normal operation

Showing compliance to the IBC seismic regulations is a bit more complicated, since the code does not accept testing on a sample unit, and each individual air handler must show compliance as constructed. This means that the designer must take into consideration the site's seismic hazard, the soil conditions at the site, the unit's location within the building and the unit design itself before a determination can be made whether or not the air handler meets the code. Climate Craft has published a white paper discussing the complexities of this process:



In both cases, Climate Craft benefits greatly from its industry-leading cabinet design with doubly-reinforced standing seam joints:



Climate Craft's superior cabinet design ensures a superior performance on site.

For Your Inner Math Geek

I offer no apologies.

Added Conversion Tables to Blog

I've added a bunch of conversion tables like the one below to the blog.

They are all located right here.

POWER CONVERSIONS

From:	To:
watt [W]kilowatt [kW]horsepower [hp]horsepower (boiler)horsepower (electric)horsepower (water)Btu (th)/hourMBHton (refrigeration)volt ampere [V*A]	watt [W]kilowatt [kW]horsepower [hp]horsepower (boiler)horsepower (electric)horsepower (water)Btu (th)/hourMBHton (refrigeration)volt ampere [V*A]
Result:
power conversion factors provided by unitconversion.org

Direct Drive, Evolved

Previous articles on this site have discussed the advantages of direct-drive plug fans and the technical tricks required to apply them correctly. However, despite their many advantages, there are times that direct-drive fans just haven't made sense.

In large part, this is because direct-drive fans have been applied as if they were belt-drive fans. It turns out, however, that there is a better way to apply these fans.











See, the problem with direct-drive is that due to the peculiarities of motor performance (discussed in the links above) you usually want to select your fan at a design speed very close to a synchronous motor speed (900, 1200, 1800 rpm, nominally). This limitation can be made up for by varying the width of the fan wheel, but this can cause an unacceptable decrease in static efficiency, or an unacceptable increase in fan noise. Or it can lead to the use of an oversized, less readily available low-rpm motor.

Another strategy is to consider selections of multiple fans, which opens up more design possibilities. However, in standard HVAC designs, this option has practical limits in the number of fans that can be arranged in a cabinet. In the traditional belt-drive paradigm, one or two large fans are mounted on the air handler floor. In unusual situations, three or more fans can be arranged this way, but this requires unusual cabinet geometries that are not often appropriate. This limits the number of direct-drive solutions that can be brought to bear, limitations that are not present with the infinitely-variable fan speeds that are available with belt-drive equipment.

But with a deceptively simple re-thinking of a traditional fan mounting, it becomes possible to stack fans one above another in an air handler cabinet--and suddenly a whole new universe of design solutions present themselves.

It is this evolved fan mounting that is the basis of the ClimateCraft Matrix system.

Matrix is an array of direct-drive plug fans designed to allow maximum flexibility in the selection of fan performance to maximize the benefits of direct drive without the traditional tradeoffs that used to be required. Five fan wheels between 16 and 27 inches are available, with motor sizes between 3 and 30 hp. The fan wheels are AMCA-certified welded aluminum wheels. The wheels are ‘modified class II’ to cover up to 11” static, or class III for higher pressures. The motors are premium efficiency, VFD compatible, 1600V insulation, ODP or TEFC—off the shelf replaceable.

An obvious temptation when mounting multiple, small fans is to avoid the costs associated with isolation and to mount them rigidly to the air handler itself. This simplistic approach, however, can result in repercussions downstream. In fact, the ASHRAE Applications handbook, chapter 47 recommends spring isolators on fans operating above 500 rpm with brake HP below 40. The issue isn’t so much transmitted vibrations, although that certainly can be a problem, but instead bearing life. Strong vibrations can kill bearings, and when the fan bearing is also a motor bearing as is the case in direct-drive plug fans, a bearing failure can be awfully expensive. Climate Craft avoids this problem by isolating every fan from the air handler structure with a unique three-point, seismically-restrained spring isolation system to prevent developing harmonics and creating damaging vibrations. But they have taken the effort even further and used a finite-element analysis to ensure that no harmonic frequencies exist in their fan base anywhere in the operating RPM of their fan systems. This step essentially converts every individual fan base into an inertia base.

This measure ensures that no VFD frequency lock-outs are needed to prevent violent vibration at the fan—a step that is often overlooked in commissioning and can cause unacceptable rates of motor failure. The unique isolator design has the added benefit of preventing the fan base from contacting the seismic restraints and causing a short-circuiting of the fan vibration directly to the frame of the unit and thus the building. This sort of grounding out of the seismic isolation is common on variable airflow systems where the fan thrust changes depending on the fan speed required at any given service point.

The Matrix allows fans to be stacked in towers 1, 2 or three high inside an air handler cabinet. Multiple towers can be installed across the air handler air tunnel. Since the fan wheels are much smaller than typical for the air handler size, many such towers can fit horizontally where only one or two typically sized fans could fit before. These fan towers are designed so that only two different designs are required to support all five different fan wheels and any required motor frame. This greatly aids in construction, making this approach a very cost competitive approach to fan mounting. The towers also serve as a rigid support truss for the fan inlet wall to support the interior of the unit at a location where the pressure differences are often quite high.

Operator Benefits

This sort of a change in fan concept represents a significant advantage for the operator of these systems. This system enhances the air handler’s reliability and serviceability. Redundancy is almost total, since in multiple-fan arrays, the loss of a single fan can often be overcome by the remaining fans simply by ramping up the RPM slightly. Replacement of a failed motor is also much easier. First of all, Matrix uses off-the shelf motor sizes that are easily obtainable on short notice. So simply getting a replacement is easier. Additionally, a typical Matrix motor and wheel assembly might weigh 150 lbs and be easily maneuvered into place by a couple of men, while a typical large fan motor may weigh 1500 lbs or more, and require special rigging to get into place. This may require a significant facility shutdown or even crane work in some cases.


Additionally, the multiple fan array allows shorter air handlers, making a more efficient use of valuable facility square footage. The smaller, faster fans also shift the acoustical signature of the system into higher octave bands, making sound attenuation easier and less expensive.

And a maintenance person will never have to tighten or align a belt on a Matrix system.

Matrix is the next evolution in fan system design.

Labs 21 Highlights Benefits of Low Pressure Lab Ventilation Design

Labs21 is the leading organization focusing on low-energy, sustainable laboratory design. Cosponsored by the EPA and the DOE, Labs21 has their sights set on these highly energy-intensive buildings and strives to find technically sound solutions to minimize the energy impact of these facilities without sacrificing their mission.

And Labs21 has set their sights on pressure drop.



Their document, Low Pressure Drop HVAC Design for Laboratories, identifies huge opportunities for savings by paying attention to this design criteria. They feel that 30-65% of the laboratory HVAC energy use could be saved by designing low pressure drop into these systems.

Tek-Air's inherently low-pressure drop air-valves can be an integral part of a low-pressure lab HVAC design, and one of the few identified that is essentially cost-neutral.

'Green' is where the lab market is going. Labs21 can help point your way there.

Aaon Helps Project Achieve LEED Platinum

Signature Center, in Golden Colorado, recently received a LEED™ Platinum rating. This ambitious goal was realized with inspired design, and wise choice of mechanical systems.

The design featured:

• Underfloor Air Distribution
• Chilled Beams
• Evaporatively Cooled Chillers with Variable Speed Pumping
• Evaporatively Cooled Rooftop DX Air Handlers
• Non-CFC R-410a Refrigerant
  

Aaon made a natural choice because of their commitment to efficient packaged equipment. This project utilized a packaged LL Chiller Plant as well as a penthouse-type RL air handler. Both units utilized Aaon's unique, water-saving evaporative condensing system. Major project savings were achieved not just in energy, but in this other increasingly scare resource.

Not only did this project reach LEED™ Platinum--It also received the 2007 top award in the institutional building category from the Colorado Renewable Energy Society (CRES).

You can read more about this notable project in this Aaon case study.

'Greening' Lab Design

Laboratory fume hoods are energy intensive. In order to provide safety for their operator, they need to ensure a constant face velocity of air at the sash--air that must first be conditioned to keep the space temperature acceptable for comfort, moved via mechanical means to the lab, and then exhausted out of the building.

A common comparison used to highlight the energy costs of these systems is to compare the energy impact of a single fume hood with that of a typical US household. On average a single lab fume hood uses as much energy as three typical US houses. And when you consider that a given facility may have many lab hoods in a single laboratory space, you can see how these energy impacts quickly add up.


In order to minimize the wasted energy associated with these laboratories, high-precision VAV lab controls have been developed to ensure operator safety, and to only provide the minimum amount of air necessary--And great savings have been realized by this sort of measure. But the energy efficiency of these systems can be improved even more.

Once the airflow has been taken down to a minimum, the energy associated with conditioning that air has been greatly reduced. But the energy associated with moving that air still can be reduced further. ASHRAE 90.1 states:

ASHRAE Standard 90.1 - 6.5.3.2.3:
“For systems with direct digital control of individual zone boxes reporting to the central control panel, static pressure setpoint shall be reset based on the zone requiring the most pressure; i.e., the setpoint is reset lower until one zone damper is nearly wide open.”

This calls for static pressure reset for VAV systems to minimize fan energy--ensuring that only the minimum amount of static pressure is provided to move the air. And this strategy is perfectly applicable to laboratory VAV systems as well as commercial air conditioning--as long as the system components are selected appropriately.

Tek-Air has published a white paper entitled Demand Based Static Pressure Reset Control for Laboratories That explores the energy benefits of this type of control scheme.


This paper analyzes system component selection, including control valves and sensors and illustrates the impact of these decisions on the overall energy use of the VAV system. In an analysis of a 50,000 cfm exhaust system, the reduced static from a pressure reset strategy can result in nearly $9,000 per year savings in fan energy (based on 0.75" savings, and $0.06/kwh electric costs).

These sorts of static pressure savings are easily attainable with a wise selection of air valve components. The commonly specified venturi-type valve has a minimum operating pressure that prevents these savings from being realized, and this added pressure drop often creates objectionable noise, which requires even more pressure drop for the system in the form of sound attenuators. This pressure reset strategy requires valves that can operate accurately and safely at low pressures.

The Tek-Air PRD valve provides unmatched pressure performance, and a quick examination of a cross section of the valve shows why:


Each blade of the damper is a smooth airfoil, greatly reducing turbulence and keeping the pressure and acoustic profile of the valve to a minimum.

If pneumatic air is not available, Tek-Air's new Accuvalve provides very similar performance with the convenience of electronic actuation. (And it won an innovation award at the 2008 AHR expo!)



A peek at the cross section of this valve shows how it attains these low pressure drops:


The airfoil shape of the valve assembly assures minimal pressure drop and sound generation for great efficiency in the fan system.

Energy savings cannot come at the cost of safety, and it is imperative that systems utilizing this method of pressure reset have sensors that can operate accurately and effectively in a wide range of pressure regimes. Tek-Air uses vortex shedding flow sensor technology to ensure the most accurate and linear control on the market.

Energy conservation is only going to become a bigger and bigger issue for designers of all building systems, and fume hood systems are a large opportunity for savings. It is important that designers and owners consider all the impacts of their design decisions and their system selections.

(Don't forget about checking the fan for stability: See this article for a review on this issue.)