Custom Air Handling Units | 4 Reasons to use Direct Drive Fans

Q. I am designing a lab exhaust system and using Strobic fans. What standards, both ASHRAE and otherwise, should I be using as a reference?

A. Below are a list of standards related to laboratories and laboratory ventilation:

NFPA-45 – Fire Protection for laboratories

UL 705 – standard for Power Ventilators in accordance with the National Electrical Code and NFPA 70 (electrical safety)

ANSI Z9.5 – Laboratory ventilation guide

ASHRAE Laboratory Design Guide

ANSI / AMCA Standard 204-05 – Balance Quality and Vibration Levels for Fans

IBC – International Building Code

ASCE 7-05 – Minimum Design Loads for Building and Other Structures. Seismic design criteria are found here.

ASHRAE Standard 110 – Testing Laboratory Fume Hoods.

AMCA 210 – Standard for fan performance testing

AMCA 260 – Standard for entrained air testing

AMCA 300 – Standard for fan sound testing

SMACNA – Duct design standards

Further questions, make sure to Ask Rick.

Custom Air Handling Units | 5 Reasons to use Custom Air Handling Units

Posted February 28, 2012 by Jim Shiminski

Custom Air Handling Units (AHU’s)

Here’s a look at why engineers and owners choose to use them.

Quality: Custom Air Handling Units are built to last longer. They have significantly better fit and finish. Units fabricated from all aluminum bases and casings, like those from Air Enterprises, have a similar life as a building (50 or more years versus about 20 years for standard packaged equipment).
Higher Pressures: Custom units are built to handle higher pressures; hence, in applications that may involve multiple filters and higher pressure requirements, they are preferred.
Lowest Life Cycle Cost: Custom AHU’s usually have larger cross sections which allow for larger more efficient fan and component sizes. Optimal equipment sizing provides the most energy efficient designs and lowest life cycle costs. Paybacks of 2-5 years are typical over standard packaged equipment.
Component Selection: With a custom unit, both owner and engineer have a choice of component equipment (fans, filters, coils, humidifiers, etc). Equipment standardized across a building or company can be included in a custom unit. These choices are typically not available with standard packaged units.
Easier Maintenance: Custom Air Handling Units provide service access panels to allow for removal of coils and fans thereby allowing quick and ease of servicing over the life of the unit. They are built with more section space to allow for maintenance access. Maintenance on custom units is significantly easier.

Custom AHU’s have a longer useful life, require less energy, and are more reliable and serviceable. In 24/7 applications we have seen simple paybacks around 2-5 years when compared to conventional AHU’s.

Typical for Custom Air Handling Units:

Construction Features:
    Precision Built Construction (All-Aluminum construction preferred)
    Structural, Low-Leakage Casing
    Structural Unit Base with Fully Welded Floors
    Tight-Sealing, Easy Open Access Doors

Component Features:
    High quality energy recovery components
    Industrial, High Efficiency Fans
    Premium Performance Motors
    Enhanced Coil Features
    Industrial Grade, Low-Leakage Dampers
    Structural Filter Assemblies

At DAC Sales we have designed and provided custom air handling units for hundreds of applications throughout New England. Contact us for more information.

If you have any Air Handling Unit questions, feel free to Ask Rick.

Energy Saving VAV Diffusers | 6 Options for Building Automation Systems

Posted February 27, 2012 by Jim Shiminski

We have worked with Variable Air Volume (VAV) Diffusers from Acutherm for 20 years now (they have been around since 1978). In the start there was one option; a stand alone Thermally Powered VAV Diffuser. It was called the Therma-Fuser. That was it and it worked very well. Today we have choices.

There are at least six ways to design a system and a fairly wide range of Building Automation System (BAS) options available. Whether you’re looking for simple individual temperature control, requiring no energy for operation, or a full-scale networked system, it’s available now. Here’s a brief overview of the six basic options.

Acutherm Therma-Fuser

Option 1: Therma-Fuser™ stand alone diffusers
This is as simple as it gets. This configuration provides the comfort and energy savings of individual temperature control at the lowest cost available. Low cost and low maintenance makes it a long time favorite. In this case the BAS is simply controlling supply air temperatures to the VAV Diffusers.

Option 2: Therma-Fuser™ stand alone diffusers with Room Temperature Sensors
Same as above and also monitoring room air temperatures with the BAS. The BAS can read an analog room temperature signal from a sensor installed in each diffuser. In this case the BAS is simply monitoring the system and controlling air temperatures.

Acutherm Digital Wall Adjusters

Option 3: Therma-Fuser™ stand alone diffusers with Wall Adjusters
Adjust room temperature set point with the BAS.
The BAS can read and reset the room temperature setpoint of each diffuser using analog signals from an Acutherm Wall Adjuster. The Wall Adjuster may be installed on the diffuser or on the wall and may be either wireless or wired to the diffuser.

Option 4: Therma-Fuser™ stand alone diffusers with Room Temperature Sensors and Wall Adjusters
A combination of Options 2 and 3, this option monitors room air temperatures and adjusts the setpoint with the BAS. The BAS can read an analog room temperature signal from a sensor installed in each diffuser and can read and reset the room temperature setpoint of each diffuser using analog signals from an Acutherm Wall Adjuster.

Option 5: Combination of Therma-Fuser™ stand alone diffusers with Therma-Fuser™ DDC interoperable diffusers
This option offers complete BAS digital input and output on selected diffusers and the simplicity of no wiring to the others. Key spaces are monitored and controlled by the BAS. Other spaces have the benefit of simplicity and low installation cost due to no diffuser wiring.

Option 6: Therma-Fuser™ DDC Interoperable diffusersThis option offers complete BAS digital input and output.
Each diffuser has the ability to supply room temperature, airflow and supply air temperature and receive signals for room temperature setpoint, minimum airflow setpoint, maximum airflow setpoint, override open, override closed, CO2 override and more. Digital signals can be either BACnet or LonWorks.

Take a look at the complete design guide: Acutherm BAS Design Guide

Have more questions, askRick?

Ask Rick: Energy Recovery Wheels on Laboratory Fume Hood Exhaust?

Posted February 24, 2012 by Carol Meader

Q. I am working on a laboratory system. I have several fume hoods and general lab exhaust. I need to incorporate energy recovery. Can I use an energy recovery wheel for this application?

A. We have done a significant number of laboratory fume hood exhaust systems using Energy Recovery Wheels. Of all the air to air energy recovery devices, the energy recovery wheel provides the highest performance (typically 70 to 80% effectiveness). That’s because the energy recovery wheel is the only true enthalpy (water) transfer device. If the application runs in the summer, like most labs, we prefer to use a wheel.

If you use a high quality energy recovery wheel and design the air handling unit correctly (supply fan in blow thru and exhaust fan in draw thru) then cross contamination is kept at a minimum. In most cases the fume hood exhaust stream is significantly diluted by all combined exhaust. If a spill were to occur in a hood it would be nearly impossible for contaminant to be carried back to the supply side. We have done analysis on this and not seen contaminant carryover reach NIOSH threshold limit values (TLV).

Here are Key design elements that we include when specifying Energy Recovery Wheels in lab applications:

Heavy Duty Wheel Structural Frame and Casing – designed and manufactured to allow a maximum rotor deflection of 1/32 inch
Include a Purge Section to eliminate transfer of containment from exhaust air into the supply air. Make it field adjustable.
Wheel Media must be Aluminum Construction
Include only 4Å or 3Å molecular sieve desiccant (size depending on application)
Require a 10 Year Warranty for the Energy Recovery Wheel
Design AHU fan arrangement with supply fan in blow thru and exhaust fan in draw thru (this way any leakage flows to the negative, exhaust side of the AHU)

There are other features that we incorporate into our Laboratory Air Handling Units that make them even more energy efficient. Have questions, askRick?

Other Resources:
Thermotech -Energy Recovery Wheel Specification for Lab Quality Energy Recovery Wheel.
Related Post: Ask Rick: How much cross contamination occurs with an Energy Recovery Wheel?

Ask Rick: High Performance Fume Hoods | Are Pass Thru Fume Hoods considered High Performance Hoods?

Posted February 22, 2012 by Jim Shiminski

Q. Are pass thru fume hoods considered ‘High Performance Hoods’?

A. Pass Thru Fume Hoods are not high performance hoods. Under good conditions, with one sash open between 12” and 18”, the hoods can contain at lower velocities. But, performance is different for each installation and dependent on lots of variables. To achieve maximum hood performance our experience shows that the air flow amount needs to be field adjusted for each pass thru hood.

Pass Thru Fume Hoods have a sash on opposite sides allowing users to access the work surface from either side. They are very practical in some applications and look really cool. They are also some of the most difficult hoods to design into Lab HVAC Systems. It is critical to operate a Pass Thru Fume Hood with one sash closed at all times. That’s how they are designed to work. Alarms can be provided to warn users of improper use (both sides open at once).

Air Sentry High Performance Teaching Hood from Lab Crafters

An alternative to the pass thru hood is the teaching hood. On a teaching hood the baffles are clear to allow viewing through the back of the hood (see photo). The teaching hood can be designed as a High Performance Fume Hood.

Feel free to follow up with comments. Post additional questions on High Performance Fume Hoods to askRick?

Project Snapshot: Lawrence Memorial Hospital | Custom Air Handling Unit

Posted February 20, 2012 by Jim Shiminski

Project:	Lawrence Memorial Hospital
Mechanical Engineer:	Thompson Consultants, Inc.
Mechanical Contractor:	Fraser Engineering
Manufacturer:	Air Eenterprises
Equipment:	Custom Air Handling Unit
Size:	65,000 CFM Unit
DAC Sales Engineer:	Steve Shelley

Project Highlights:

Constraints:
The existing air handling units in the mechanical room that served the hospital and OR suites had exceeded their useful life and needed to be replaced. The hospital could not shut down operations for a retrofit of the existing units in place.

Solution:
A new Air Enterprises Custom Air Handling Unit with a service vestibule was located on a roof curb above the existing mechanical room. A service vestibule was provided for accessibility and serviceability for a roof mounted piece of equipment. The service vestibule contained all the piping as well as the electrical panels, VFDs and control panels.

All the piping was factory installed and insulated. This reduced the amount of field labor required to install the unit. It also limited the amount of time to cut over the new unit and integrate it into the existing systems. The piping was fully coordinated at the factory to maximize service space within the corridor.

After the new Custom Air Handling Unit was operational the existing units were decommissioned on a phased schedule to minimize impact on the hospital’s operation.

The unit was all aluminum construction to provide the maximum life for a roof top mounted piece of equipment. Air Enterprises provided a 40 year casing guarantee.

Have questions on Custom Air Handling Unit Design, askRick?

Ask Rick: What is adiabatic humidification?

Posted February 13, 2012 by Carol Meader

Q. What is adiabatic humidification?

A. There are two basic ways to introduce moisture into air:

Isothermal Humidification – the water vapor is dispersed in the air after having been created by boiling water. Isothermal humidification requires an external source of energy to change the state of the water. In the commercial HVAC world Isothermal Humidification has been used for years in nearly all applications.
Types:
– Direct Steam Injection
– Steam-To-Steam
– Gas-To-Steam
– Electric Steam
– Infra-Red

Adiabatic Humidification – finely atomized water is introduced into the air. The adiabatic process does not involve the contribution of thermal energy from an external source. There is no heat added.
Typical Types:
– High Pressure Atomizing
– Air/Water Atomizing
– Ultrasonic
– Wetted Media Evaporative

The biggest advantages of Adiabatic Humidifiers are:

Significant Energy Savings.
Helpful when Steam or Gas are not available
Precise Humidity Control.
Easy to Install and Retrofit.
Proven and Simple Technology.
Simple to Operate and Maintain.

Disadvantages seen in Adiabatic Humidifiers are:

Longer Absorption Distances (more length need in an air handling unit)
Requires Preheat of Supply air
Typically Require RO Water
Compressed Air required on Air/Water Systems

See manufacture information from Carel for more information on Humidifier types.

Ask Rick with further questions about Adiabatic Humidification.

Ask Rick: Should I use a bypass damper on an Energy Recovery Wheel?

Posted February 13, 2012 by Carol Meader

Q. Should I use a bypass damper on an Energy Recovery Wheel?

A. We typically use a bypass damper around a energy recovery device for frost control and economizer. That is typical for Heat Pipes and plate exchangers. In the case of an Energy Recovery Wheel we typically slow the wheel down to minimum speeds to allow for both frost control and economizer.

Bypassing the wheel in economizer would be less pressure drop and could create savings. The problem is that the unit casing has to grow to accomplish this. After careful study we have found that it is not cost effective to make the Energy Recovery Unit casing larger just to install a bypass for the wheel.

Steam Humidification | Energy Efficient – Short Absorption Steam Humidification

Posted February 9, 2012 by Jim Shiminski