DAC Sales Blog
Posted by Jim Shiminski on April 15th, 2012
In 20 years of business we have been involved in supplying nearly 100 Field Erected Air Handling Units. They come in all shapes and sizes and are used in lots of different applications.
Here are the top 4 reasons why field erected units make sense:
- They Fit - It’s very typical that worn out air handling units exist in the bowels of a building. They cannot be replaced by a traditional factory built unit. Site Assembled Units are typically rigged through elevators, hallways and doorways. This construction technique often allows for a larger unit to be built in place to increase capacity.
- They Fit Better - Available mechanical space is maximized by incorporating existing columns, beams and bracing into unit design. Units can be built to the full extent of the space.
- They Cost Less – Yes, believe it. If you include unit, rigging and install cost, then field erected units usually cost less than factory built units.
- They have Shorter Lead Times - Lead time for a site-assembled unit is always less than a factory built unit. Lead times are reduced to the timing of the longest lead time item like fans or coils. 4 to 6 weeks is possible for a custom field erected unit.
Assembling the air handling unit in place provides a cost-effective installation of the preferred air handling system in the preferred location without additional project costs (like knocking down walls) or unacceptable technical sacrifices.
Field erected air handling units utilize the same high quality components used in factory assembled units. Panels and extrusions that makeup the casing system, equipment sub-assemblies and structural unit base sections are factory fabricated exactly as for a factory assembled unit. These pieces are sized and transported on skids to accommodate the rigging limitations of freight elevators, door sizes, hallways or low ceilings, mini
mizing the impact on existing structures. Field erected units are final assembled under the direction of factory trained supervisors.
In the end it’s very difficult to distinguish a field erected unit from a factory built unit.
More questions on field erected air handling units; askRick
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Posted by Jim Shiminski on April 4th, 2012
Q. I have some questions about pumped glycol systems. What happens if all the entrapped air is not removed from the glycol? Should a closed loop have auto bleed?
A. Air bubbles entrapped in the glycol circuit are very detrimental to the thermal performance of the energy recovery system. It causes the heat transfer coefficient in the coil tubes to drop dramatically. In fact, it doesn’t take a lot of air in the glycol circuit to get the thermal energy recovery reduced to less than the pumping energy, turning the energy recovery system in a net energy consumer.
The Konvekta system has several safeguards to insure this is not happening:
- The glycol pumps are equipped with air separators
- A sight-glass on the Hydronic Unit allows the operator to see whether air is in the glycol
- The controller will detect the reduced thermal performance and alert the operator to the problem
Also, according to good engineering practice, air vents are designed at the high points of the piping to allow de-airation if necessary.
Rudolf Zaengerle, Ph.D.
President, Konvekta USA Inc.
5 Independence Way, 3d Floor #95
Princeton, NJ 08540
Phone: 724 462 8207
More questions about Pumped Glycol Energy Recovery Systems, askRick?
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Tags: Pumped Glycol Energy Recovery, Pumped Glycol Run Around Loop, pumped glycol systems
Posted in Ask Rick, Energy Recovery, Pumped Glycol Systems, Show | No Comments »
Posted by Jim Shiminski on April 3rd, 2012
Q. How does a high pressure atomizing humidifier work?
A. Atomizing humidifiers like the Carel humiFog systems utilize a high pressure (1,000 psi) pumping system to pressurize treated water and pump it to atomizing nozzles. The nozzles then reduce the water jet into a very fine water droplet (10-20 microns). Due to the fine droplet size the water can easily change its state into a vapor. The energy required for this transformation in state is provided by the ambient air.
There is a decrease in temperature which may be useful in many applications (adiabatic transformation).
A packaged control system controls the speed of the pump via a variable frequency drive and consequently the flow-rate of the pump. The controller activates a series of solenoid valves that open only the nozzles that are necessary, allowing the system to always operate at the ideal pressure to atomize the water, across a wide range of flow-rates.
Post by Steve Shelley
For more information on High Pressure Humidifiers askRick?
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Posted in Ask Rick, Humidification, Show | No Comments »
Posted by Jim Shiminski on March 28th, 2012
5 reasons to use All Aluminum Construction for Custom Air Handling Units?
Lawrence Hospital - Air Enterprises Unit All Aluminum Construction
- Aluminum provides excellent corrosion resistance without the need for paint.
- Painting and galvanization can be scrapped off during transportation, rigging and assembly of the unit.
- Rust and corrosion reduce the structural integrity of the unit.
- Low Weight - Aluminum construction can reduce overall unit weight by as much as 40%.
- Reduced Rigging Costs
- Reduced structural support costs
- Longer life
- Aluminum equipment has a more than 40 year life expectancy
- Galvanized equipment has a 25 year life expectancy
- Less impact on the environment
- Install one unit in forty years not TWO!
- Air Enterprises- 40 year non-corrosive Guarantee
Post by Steve Shelley
For more information on Custom Air Handling Units, askRick?
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Posted by Jim Shiminski on March 26th, 2012
Project Challenge:
This was a new building project. The engineer, owner and contractor were all looking to create a design that provided the maximum energy savings while meeting the Mass. Energy Code. The preliminary design called for 4 separate 30,000 CFM Make-Up Air Handling Units (AHUs) and 2 each Strobic Air Exhaust Energy Recovery Units (ERU’s). The total system air side was 120,000 CFM. The original design included a pumped glycol energy recovery loop connecting each AHU to respective ERUs. We did a preliminary estimates and determined that the energy recovery effectiveness would be about 45% for this system. After subtracting out pumping energy the net effectiveness was expected to be closer to 40%.
Solution:
In this case we proposed to combine both supply and exhaust into one unit. Instead of pumped glycol energy recovery we designed a Heat Pipe from Heat Pipe Technology into each of the units. The Energy Recovery Air Handling Units were each sized for 30,000 CFM on both the supply and exhaust side. The major advantage of this system was that it incorporated the use of a heat pipe to recover 65% of the energy from the exhaust air stream. The costs for the two proposals were comparable after including the piping costs into the pumped glycol solution.
Result:
The revised design was a much easier install. The resulting system is at least 50% more energy efficient. The units are all aluminum construction. The owner now has a passive energy recovery system that does not have to be maintained. That is a huge plus.
For questions on Energy Recovery Air Handling Units, askRick?
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Posted in Energy Recovery, Heat Pipes, High Plume Dilution Fans, Lab Design, Project Snapshots, Show | No Comments »
Posted by Jim Shiminski on March 21st, 2012
Q. What is a typical pressure drop across the Konvekta coils?
A. The air pressure drop across the coils depends on several factors: number of rows, air face velocity, fin spacing and tube alignments. There is a trade-off between thermal efficiency and air pressure drop which will be one of the design considerations if we know the price of heat ($/MBTU) and the price of electricity (fan power). Typically, one can expect an air pressure drop in the range of 0.4″ to 0.7″.
Rudolf Zaengerle, Ph.D.
President, Konvekta USA Inc.
5 Independence Way, 3d Floor #95
Princeton, NJ 08540
Phone: 724 462 8207
More questions about Pumped Glycol Energy Recovery Systems, askRick?
Posted in Ask Rick, Energy Recovery, Pumped Glycol Systems, Show | No Comments »
Posted by Rick McGinley on March 17th, 2012
Q. The commissioning engineer has commented that the Heat Recovery Unit (HRU) does not meet the 25’ separation distance between the Intake hood and Exhaust Discharge requirement.
I believe that our design with the effective plume height of 44’ and the fan discharge 16’ above the inlet of the intake hood is better than a fan 25’ away from an intake. We know that plumes do not come straight down. Do you have any comment regarding separation of air intakes from exhaust discharge or have you seen this type of issue before and provided helpful information?
A. We recognize the recommendation in ASHRAE Standard 170-2008 (the Ventilation of Healthcare Facilities) which calls for recommended distance offsets between exhaust stacks and air intakes (placing an exhaust discharge 25′ from an intake). This recommendation serves as a very useful guide to engineers. It’s language is seen in other standards and shared by local standards as well.
In practice it is not practical to use this recommendation when evaluating High Plume Dilution Fans, like the Strobic Air Tri-Stack Fans. The Tri-Stack Fan uses a patented nozzle design to maintain stack velocities while minimizing horsepower. Increased stack velocities allow the fan to entrain outside air (up to 170% by volume). Process air and entrained air combine to produce a significantly higher effective stack height (the physical height of the equipment plus the plume height.). This stack height calculation is used by wind consultants and CFD dispersion models worldwide. The ASHRAE Standard 170-2008 does not take this stack height calculation into account and therefore should not be applied to a High Plume Dilution Fan type applications.
With High Plume Dilution fans, like the Tri-Stack Fan, we have found that the safest place to position a fan is in close proximity to the building intakes. This insures that the diluted exhaust air will be driven up and away from the intakes. We recommend that the fan discharge velocity be maintained at 3,000 FPM per ANZI Z9.5.
Strobic Air has hundreds of laboratory fans that are located less than 25′ from air intakes. We have many of those here in New England. In 26 years Strobic Air has never experienced a single instance of re-entrainment on a laboratory.
Further questions about Laboratory Exhaust Fans - askRick?
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Posted by Jim Shiminski on March 13th, 2012
Konvekta is the only supplier of high efficiency pumped glycol run-around energy recovery systems in the world. They have been in the business of pumped glycol energy recovery since 1949. That’s all they do. Konvekta offers complete systems – high performance heat exchangers, energy recovery system controls and hydraulic assembly.
The Konvekta coil design is unlike all others – it is truly a high performance heat exchanger. Prior to using this coil we would select standard water coils for all pumped glycol applications. They were the best choice we had.
There are issues involved in selecting standard water coils for glycol heat recovery applications
- Standard water coils always get selected for a degree day that is worst case scenario and never happens. Standard coils are not optimized for the temperatures that they are actually working at.
- Standard water coils are generally 8 rows or greater so pressure drops are significant.
- Decreasing flow through a standard water coil with a variable frequency drive (which would optimize heat transfer) , is not possible. As velocity of glycol slows and becomes partially or completely laminar, the heat transfer coefficient drops significantly.
- Bottom Line – Standard water coils are not designed for Pumped Glycol Energy Recovery Applications
Konvekta Coil - Dartmouth College Burke Hall
Konvekta High Efficiency Heat Exchanger
Features:
- Fin-tube heat exchanger with header at both ends
- Optimized Fin Design – thick, flat, wide-spaced fins
- Selected for optimal temperature performance range (not a single point)
- Corrosion protected
Benefits
- Almost pure counter-flow for highest energy transfer
- Low Pressure Drop
- Fin Design provides high heat-transfer factors
- Dual Headers create a high glycol Reynolds number to assure turbulent flow under all operating conditions
- Design offers a very small air-to-glycol approach temperature difference to maximize heat transfer
- Entire depth of coil accessible for cleaning
Konvekta Coils - Dartmouth College Burke Hall
The biggest design features that achieve these benefits are headers on both ends of the coil and thick, flat, wide-spaced fins. This coil is typically 10% more efficient than a standard water coil when used in run-around energy recovery applications.
If you have more questions feel free to askRick?
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Tags: coil, coils, energy, energy conservation, energy recovery, energy recovery systems, glycol, heat exchanger, heat exchanger coil, heat recovery, heat recovery ventilation, heat transfer, heat transfers, heating, konvekta, pumped glycol systems, ventilating
Posted in Pumped Glycol Systems, Show | 2 Comments »
Posted by Jim Shiminski on March 12th, 2012
Project Highlights:
Prior Conditions: Most of the areas of the engineering, manufacturing, assembly, test, inspection and packaging areas were all being served by 2 large central Air Handling Units (AHUs) running constant volume. Manufacturing equipment and machines located at the southern end of the building could never get enough cooling during warmer months. At the same time some interior zones such as inspection area, where people work, were often cold. While there was a Heating mode it was rarely used because the facility generated considerable interior heat load year round.
The VAV Solution:
Premium efficiency motors and Variable Frequency Drives (VFDs) had already been added but a means to distribute and modulate the conditioned air to the all open areas was needed. Bluestone engineers worked with DAC Sales and Acutherm Engineers on a simple retrofit solution. The fix was to replace the old constant volume diffusers with Acutherm VAV Therma-Fuser modules. The VAV Therma-Fuser modules with built in space sensing 
elements could automatically modulate to deliver the precise amount of conditioned air to the local area. Being applied to an exposed duct system, the new Round Therma-Fuser ST model was chosen in most areas while some used standard 2 X 2 ST square units.
The Results:
Now the machinists state they are finally cool and comfortable. The over-conditioned spaces are gone. This results in energy savings at the AHUs and reduced chiller load. During partial load days the Therma-Fuser modules are near the field set minimum position at many locations. This “back-up” of air in the duct increases SP which signals the VFD to back down thus saving on fan energy.
A chiller replacement rounded out the project and utility rebates were included to United Electric for stepping up with an aggressive energy measure program.
To learn more about Acutherm Therma-Fusers contact David Goodman
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Posted by Jim Shiminski on March 8th, 2012
We do our best to design the most Energy Efficient HVAC systems. If possible, we will always pick a Direct Drive Fan over a Belt Driven Fan for a Custom Air Handling Unit.
Here are 4 Reasons why we choose Direct Drive Fans:
- Energy Savings: Eliminating drive losses from the belt and pulley can improve mechanical efficiency by up to 5%.
- Lower Maintenance: A direct drive fan requires minimal maintenance. The routine maintenance of lubrication and belt tensioning is eliminated.
- Motor Longevity: By nature of design, Direct Drive Fans must be controlled by a Variable Frequency Drive (VFD). The controller acts as a soft start, greatly reducing the stress on the motor, and in turn minimizes the risk of motor failure.
- Low Noise Level: Much of the noise in ventilation units is created by the moving belts. Without a belt, the sound level is frequently lowered by 3-9 dBA. As a
result, sound attenuation components can be smaller, and in some cases can be eliminated. Smaller sound attenuators decrease the degree of static pressure drops. Savings are in both initial installation cost and in improved system efficiency
There are other reasons to use Direct Drive Fans in HVAC applications but these are the most common. Be aware that Direct Drive Fans should also be used in standard packaged air handling units for the same reasons.
Related Post: Ask Rick: Why aren’t direct drive fans used on more applications?
More questions about Direct Drive Fans; Ask Rick?
Tags: air enterprises, air handler, air handling unit, and air conditioning, belt driven fans, custom air handling units, direct drive, direct drive fan, fan, fans, heating, hvac, mechanical engineering, variable frequency drive, ventilating, ventilation
Posted in Air Handling Units, Show | 1 Comment »
